@booklet {11954, title = {{CA2510960A1 Ophtalmic articles.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @booklet {11944, title = {{EP1611877A1 ophtalmic articles.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @booklet {11953, title = {{EP1611877A1 ophtalmic articles.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @article {Leite, title = {{No Title}}, year = {Submitted}, note = {n/a}, abstract = {n/a}, keywords = {chemical engineering department, ciepqpf, corresponding author, de sousa, dr, Drug delivery systems, herminio c, s institution, Supercritical solvent impregnation, Therapeutic contact lenses, university of}, author = {Leite, Eug{\'e}nio and Gil, Maria H. and Sousa, Herminio C De} } @booklet {11946, title = {{US2006008506A1 Ophtalmic articles.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @booklet {11951, title = {{US2006008506A1 Ophtalmic articles.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @booklet {11947, title = {{WO2015151030A1 Method to obtain collagen{\_}gelatin from marine sponges.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @booklet {11950, title = {{WO2015151030A1 Method to obtain collagen{\_}gelatin from marine sponges.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @booklet {11948, title = {{WO2016181371A1{\_}An ureteral stent and methods thereof.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @booklet {11949, title = {{WO2016181371A1{\_}An ureteral stent and methods thereof.pdf}}, year = {Submitted}, note = {n/a}, abstract = {n/a} } @article {Duarte2017a, title = {{A comparison between pure active pharmaceutical ingredients and therapeutic deep eutectic solvents: Solubility and permeability studies}}, journal = {European Journal of Pharmaceutics and Biopharmaceutics}, volume = {114}, year = {2017}, note = {n/a}, pages = {296{\textendash}304}, publisher = {Elsevier B.V.}, abstract = {

THEDES, so called therapeutic deep eutectic solvents are here defined as a mixture of two components, which at a particular molar composition become liquid at room temperature and in which one of them is an active pharmaceutical ingredient (API). In this work, THEDES based on menthol complexed with three different APIs, ibuprofen (ibu), BA (BA) and phenylacetic acid (PA), were prepared. The interactions between the components that constitute the THEDES were studied by NMR, confirming that the eutectic system is formed by H-bonds between menthol and the API. The mobility of the THEDES components was studied by PFGSE NMR spectroscopy. It was determined that the self-diffusion of the species followed the same behavior as observed previously for ionic liquids, in which the components migrate via jumping between voids in the suprastructure created by punctual thermal fluctuations. The solubility and permeability of the systems in an isotonic solution was evaluated and a comparison with the pure APIs was established through diffusion and permeability studies carried out in a Franz cell. The solubility of the APIs when in the THEDES system can be improved up to 12 fold, namely for the system containing ibu. Furthermore, for this system the permeability was calculated to be 14~{\texttimes}~10-5~cm/s representing a 3 fold increase in comparison with the pure API. With the exception of the systems containing PA an increase in the solubility, coupled with an increase in permeability was observed. In this work, we hence demonstrate the efficiency of THEDES as a new formulation for the enhancement of the bioavailability of APIs by changing the physical state of the molecules from a solid dosage to a liquid system.

}, keywords = {Diffusion coefficient, Drug solubility, permeability, Pharmaceutical and biomedical applications, Therapeutic deep eutectic solvents}, issn = {18733441}, doi = {10.1016/j.ejpb.2017.02.003}, url = {http://dx.doi.org/10.1016/j.ejpb.2017.02.003}, author = {Duarte, Ana Rita C and Ferreira, Ana Sofia D. and Barreiros, Susana and Eurico Cabrita and Reis, Rui L and Paiva, Alexandre} } @article {Fassini2017, title = {{Bioinspiring Chondrosia reniformis (Nardo, 1847) Collagen-Based Hydrogel: A New Extraction Method to Obtain a Sticky and Self-Healing Collagenous Material}}, journal = {Marine Drugs}, volume = {15}, number = {12}, year = {2017}, note = {n/a}, pages = {380}, abstract = {

Collagen is a natural and abundant polymer that serves multiple functions in both invertebrates and vertebrates. As collagen is the natural scaffolding for cells, collagen-based hydrogels are regarded as ideal materials for tissue engineering applications since they can mimic the natural cellular microenvironment. Chondrosia reniformis is a marine demosponge particularly rich in collagen, characterized by the presence of labile interfibrillar crosslinks similarly to those described in the mutable collagenous tissues (MCTs) of echinoderms. As a result single fibrils can be isolated using calcium-chelating and disulphide-reducing chemicals. In the present work we firstly describe a new extraction method that directly produces a highly hydrated hydrogel with interesting self-healing properties. The materials obtained were then biochemically and rheologically characterized. Our investigation has shown that the developed extraction procedure is able to extract collagen as well as other proteins and Glycosaminoglycans (GAG)-like molecules that give the collagenous hydrogel interesting and new rheological properties when compared to other described collagenous materials. The present work motivates further in-depth investigations towards the development of a new class of injectable collagenous hydrogels with tailored specifications.

}, keywords = {collagen rheology, Hydrogel, marine biomaterials, marine collagen, marine sponge GAG, {\textless}i{\textgreater}Chondrosia reniformis{\textless}/i{\textgreater}}, issn = {1660-3397}, doi = {10.3390/md15120380}, url = {http://www.mdpi.com/1660-3397/15/12/380}, author = {Fassini, Dario and Duarte, Ana Rita and Reis, Rui and Tiago Silva} } @article {Duarte2017, title = {{Biomaterials and Bioactive Agents in Spinal Fusion}}, journal = {Tissue Engineering Part B: Reviews}, volume = {23}, number = {6}, year = {2017}, note = {n/a}, pages = {ten.teb.2017.0072}, abstract = {

Management of degenerative spine pathologies frequently leads to the need for spinal fusion (SF), where bone growth is induced toward stabilization of the interventioned spine. Autologous bone graft (ABG) remains the gold-standard inducer, whereas new bone graft substitutes attempt to achieve effective de novo bone formation and solid fusion. Limited fusion outcomes have driven motivation for more sophisticated and multidisciplinary solutions, involving new biomaterials and/or biologics, through innovative delivery platforms. The present review will analyze the most recent body of literature that is focused on new approaches for consistent bone fusion of spinal vertebrae, including the development of new biomaterials that pursue physical and chemical aptitudes; the delivery of growth factors (GF) to accelerate new bone formation; and the use of cells to improve functional bone development. Bone graft substitutes currently in clinical practice, such as demineralized bone matrix and ceramics, are still used as a starting point for the study of new bioactive agents. Polyesters such as polycaprolactone and polylactic acid arise as platforms for the development of composites, where a mineral element and cell/GF constitute the delivery system. Exciting fusion outcomes were obtained in several small and large animal models with these. On what regards bioactive agents, mesenchymal stem cells, preferentially derived from the bone marrow or adipose tissue, were studied in this context. Autologous and allogeneic approaches, as well as osteogenically differentiated cells, have been tested. These cell sources have further been genetically engineered for specific GF expression. Nevertheless, results on fusion efficacy with cells have been inconsistent. On the other hand, the delivery of GF (most commonly bone morphogenetic protein-2 [BMP-2]) has provided favorable outcomes. Complications related to burst release and dosing are still the target of research through the development of controlled release systems or alternative GF such as Nel-like molecule-1 (NELL-1), Oxysterols, or COMP-Ang1. Promising solutions with new biomaterial and GF compositions are becoming closer to the human patient, as these evidence high-fusion performance, while offering cost and safety advantages. The use of cells has not yet proved solid benefits, whereas a further understanding of cell behavior remains a challenge.

}, keywords = {adult stem cells, growth factors, polymeric scaffolds, spinal fusion}, issn = {1937-3368}, doi = {10.1089/ten.teb.2017.0072}, url = {http://online.liebertpub.com/doi/10.1089/ten.teb.2017.0072}, author = {Duarte, Rui M. and Varanda, Pedro and Reis, Rui L and Duarte, Ana Rita C and Correia-Pinto, Jorge} } @article {Salgado2017, title = {{Development of barley and yeast $\beta$-glucan aerogels for drug delivery by supercritical fluids}}, journal = {Journal of CO2 Utilization}, volume = {22}, number = {August}, year = {2017}, note = {n/a}, pages = {262{\textendash}269}, publisher = {Elsevier}, abstract = {

Polysaccharide aerogels are a good alternative as carriers for drug delivery, since they allow high loading of the active compounds in matrices that are non-toxic, biocompatible and from a renewable feedstock. In this work, barley and yeast $\beta$-glucans aerogels were produced by gelation in aqueous solution, followed by solvent exchange and drying with supercritical CO2. First, viscoelastic properties and melting profile of the hydrogels were determined. Then, the obtained aerogels were analyzed regarding morphology, mechanical properties and behavior in physiological fluid. Both in the hydrogels and in the aerogels, big differences were observed between barley and yeast $\beta$-glucans due to their different chain structure and gelation behavior. Finally, impregnation of acetylsalicylic acid was performed at the same time as the drying of the alcogels with supercritical CO2. The release profile of the drug in PBS was analyzed in order to determine the mechanism governing the release from the $\beta$-glucan matrix. 2017 Elsevier Ltd. All rights reserved.

}, keywords = {$\beta$-glucan, Acetylsalicylic acid, Aerogel, Rheology, Supercritical drying, Supercritical impregnation}, issn = {22129820}, doi = {10.1016/j.jcou.2017.10.006}, url = {http://dx.doi.org/10.1016/j.jcou.2017.10.006}, author = {Salgado, Marta and Santos, Filipa and Rodr{\'\i}guez-Rojo, Soraya and Reis, Rui L and Duarte, Ana Rita C and Cocero, Mar{\'\i}a Jos{\'e}} } @article {Silva2017, title = {{Engineered tubular structures based on chitosan for tissue engineering applications}}, journal = {Journal of Biomaterials Applications}, year = {2017}, note = {n/a}, pages = {088532821774469}, abstract = {n/a}, keywords = {biofunctionality, biomaterials, biomimetic, chitosan, tissue engineering}, issn = {0885-3282}, doi = {10.1177/0885328217744698}, url = {http://journals.sagepub.com/doi/10.1177/0885328217744698}, author = {Silva, Joana M and Rodrigues, Lu{\'\i}sa C and Silva, Simone S and Reis, Rui L and Duarte, Ana Rita C} } @article {Barros2017, title = {{Green solvents for enhanced impregnation processes in biomedicine}}, journal = {Current Opinion in Green and Sustainable Chemistry}, volume = {5}, year = {2017}, note = {n/a}, pages = {82{\textendash}87}, publisher = {Elsevier Ltd}, abstract = {

Supercritical carbon dioxide has been used as a green solvent due to their well-known potential in biomaterials impregnation. The versatility of this technique enables the loading of implants with Active Pharmaceutical Ingredients which present several benefits when compared with traditional techniques to impregnate active compounds. In this review, we have summarized the recent progresses achieved in supercritical CO2assisted impregnation of active compounds and therapeutic deep eutectic systems for biomedical applications.

}, issn = {24522236}, doi = {10.1016/j.cogsc.2017.03.014}, url = {http://dx.doi.org/10.1016/j.cogsc.2017.03.014}, author = {Barros, Alexandre A. and Silva, Joana M and Craveiro, Rita and Paiva, Alexandre and Reis, Rui L and Duarte, Ana Rita C} } @article {Gertrudes2017, title = {{How Do Animals Survive Extreme Temperature Amplitudes? the Role of Natural Deep Eutectic Solvents}}, journal = {ACS Sustainable Chemistry and Engineering}, volume = {5}, number = {11}, year = {2017}, note = {n/a}, abstract = {

{\textcopyright} 2017 American Chemical Society. Recent findings have reported the reason why some living beings are able to withstand the huge thermal amplitudes between winter and summer in their natural habitats. They are able to produce metabolites decreasing deeply the crystallization temperature of water, avoiding cell disrupture due to the presence of ice crystals and overcoming osmotic effects. In vitro, the possibility to cool living cells and tissues to cryogenic temperatures in the absence of ice can be achieved through a vitrification process. Vitrification has been suggested as an alternative approach to cryopreservation and could hereafter follow an interesting biomimetic perspective. The metabolites produced by these animals are mostly sugars, organic acids, choline derivatives, or urea. When combined at a particular composition, these compounds form a new liquid phase which has been defined as Natural Deep Eutectic Solvents (NADES). In this review, we relate the findings of different areas of knowledge from evolutive biology, cryobiology, and thermodynamics and give a perspective to the potential of NADES in the development of new cryoprotective agents.

}, keywords = {Cryopreservation, Cryoprotective agents, Deep eutectic solvents, Glycerol, Vitrification}, issn = {21680485}, doi = {10.1021/acssuschemeng.7b01707}, author = {Gertrudes, A. and Craveiro, R. and Eltayari, Z. and Reis, R.L. and Paiva, A. and Duarte, A.R.C.} } @article {Barros2017a, title = {{In vivo assessment of a novel biodegradable ureteral stent}}, journal = {World Journal of Urology}, year = {2017}, note = {n/a}, abstract = {

{\textcopyright} 2017 Springer-Verlag GmbH Germany, part of Springer Nature Purpose: To perform an in vivo assessment of a newly developed biodegradable ureteral stent (BUS) produced with natural-based polymers. Methods: The BUS is based on a patented technology combining the injection process with the use of supercritical fluid technology. Study was conducted at ICVS{\textemdash}University of Minho (Braga, Portugal) and a total of ten domestic pigs were used. In seven animals, the experimental BUS stent was inserted, whereas in the remaining a commercially available stent was used (6-Fr Biosoft {\textregistered} duo stents, Porges Coloplast, Denmark). Post-stenting intravenous pyelogram was used to evaluate the degree of hydronephrosis. The in vivo stent degradation was measured as function of the weight loss. Moreover, the tensile properties of the BUS were tested during in vivo degradation. After maximum 10 days, animals were killed and necropsy was performed. Tissues were compared between the stented groups as well as between the non-stented contralateral ureters and stented ureters in each group. Biocompatibility was assessed by histopathological grading. Results: In all cases, the BUS was only visible during the first 24 h on X-ray, and in all cases the BUS was completely degraded in urine after 10 days, as confirmed on necropsy. During the degradation process, the mechanical properties of the BUS decreased, while the commercial ureteral stents remained constant. At all time-points after stent insertion, the level of hydronephrosis was minimal. Overall, animals stented with BUS had an average grade of hydronephrosis which was lower compared to the controls. The BUS showed better pathological conditions, and hence better biocompatibility when compared with commercial stents. Conclusions: Notwithstanding the limitations of the present study, the in vivo testing of our novel natural origin polymer-based BUS suggests this device to feature homogeneous degradation, good urine drainage, and high biocompatibility. Next steps will be to increase its stability, and to improve the radiopacity without compromising its degradation. Ultimately, clinical studies will be required to determine the safety and feasibility of its use in humans.

}, keywords = {Biodegradable, Polymers, Ureteral stent, Ureteroscopy}, issn = {14338726}, doi = {10.1007/s00345-017-2124-3}, author = {Barros, A.A. and Oliveira, C. and Ribeiro, A.J. and Autorino, R. and Reis, R.L. and Duarte, A.R.C. and Lima, E.} } @article {Barros2017b, title = {{In~Vitro and Ex~Vivo Permeability Studies of Paclitaxel and Doxorubicin From Drug-Eluting Biodegradable Ureteral Stents}}, journal = {Journal of Pharmaceutical Sciences}, volume = {106}, number = {6}, year = {2017}, note = {n/a}, abstract = {

{\textcopyright} 2017 American Pharmacists Association{\textregistered} A drug-eluting biodegradable ureteral stent (BUS) has been developed as a new approach for the treatment of urothelial tumors of upper urinary tract cancer. In a previous work, this system has proven to be a good carrier for anticancer drugs as a potential effective and sustainable intravesical drug delivery system. BUS has revealed to reduce in 75{\%} the viability of human urothelial cancer cells (T24) after 72~h of contact and demonstrated minimal cytotoxic effect on human umbilical vein endothelial cells (HUVECs) which were used as a control. In this work, we studied the permeability of the anticancer drugs, such as paclitaxel and doxorubicin, alone or released from the BUS developed. We used 3 different membranes to study the permeability: polyethersulfone (PES) membrane, HUVECs cell monolayer, and an ex~vivo porcine ureter. The ureter thickness was measured (864.51 $μ$m) and histological analysis was performed to confirm the integrity of urothelium. Permeability profiles were measured during 8~h for paclitaxel and doxorubicin. The drugs per se have shown to have a different profile and as expected, increasing the complexity of the membrane to be permeated, the permeability decreased, with the PES being more permeable and the ex~vivo ureter tissue being less permeable. The molecular weight has also shown to influence the permeability of each drug and a higher percentage for doxorubicin (26{\%}) and lower for paclitaxel (18{\%}) was observed across the ex~vivo ureter. The permeability (P), diffusion (D), and partition (K d ) coefficients of paclitaxel and doxorubicin through the permeable membranes were calculated. Finally, we showed that paclitaxel and doxorubicin drugs released from the BUS were able to remain in the ex~vivo ureter and only a small amount of the drugs can across the different permeable membranes with a permeability of 3{\%} for paclitaxel and 11{\%} for doxorubicin. The estimated amount of paclitaxel that remains in the ex~vivo ureter tissue is shown to be effective to affect the cancer cell and not affect the noncancer cells.

}, keywords = {Biodegradable polymers, doxorubicin permeability, paclitaxel, Upper tract urothelial carcinoma, ureteral stents}, issn = {15206017}, doi = {10.1016/j.xphs.2017.02.023}, author = {Barros, A.A. and Oliveira, C. and Reis, R.L. and Lima, E. and Duarte, A.R.C.} } @article {Aroso2017, title = {{Natural deep eutectic solvents from choline chloride and betaine {\textendash} Physicochemical properties}}, journal = {Journal of Molecular Liquids}, volume = {241}, year = {2017}, note = {n/a}, abstract = {

{\textcopyright} 2017 Elsevier B.V. The preparation of natural deep eutectic solvents (NADESs) from cheap and readily available raw materials is reported. In this work, we have considered mixtures of choline chloride (CC) or betaine (Bet) with 3 sugar molecules (glucose (Glu), xylose (Xyl) and sucrose (Suc)) and 2 carboxylic acids (citric (CA) and tartaric (Tart) acids). The formation of NADESs was investigated by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The CC mixtures give origin to NADESs for 1:1~M ratio with the sugar molecules and for 2:1, 1:1 and 1:2 with the carboxylic acids, while Bet mixtures only formed NADES with the carboxylic acids. The effect of water content (up to 5{\%} (wt.{\%})) and temperature in conductivity and rheology were characterized. The NADESs were found to be non-thixotropic, Newtonian liquids with high viscosity, decreasing with increasing temperature and water content. The conductivity is limited by charge carrier mobility, thus increasing with water content and temperature.

}, keywords = {Conductivity, Hydrogen bond acceptor, Hydrogen bond donor, Natural deep eutectic solvents, Rheology, Thermophysical properties}, issn = {01677322}, doi = {10.1016/j.molliq.2017.06.051}, author = {Aroso, I.M. and Paiva, A. and Reis, R.L. and Duarte, A.R.C.} } @article {Salgado2017a, title = {{Preparation of barley and yeast $\beta$-glucan scaffolds by hydrogel foaming: Evaluation of dexamethasone release}}, journal = {Journal of Supercritical Fluids}, year = {2017}, note = {n/a}, abstract = {

{\textcopyright} 2017 Elsevier B.V. Porous polymeric materials are studied in tissue engineering, because they can act as support for cell proliferation and as drug delivery vehicles for regeneration of tissues. Hydrogel foaming with supercritical CO 2 is a suitable alternative for the creation of these structures, since it avoids the use of organic solvents and high temperature in the processing. In this work, $\beta$-glucans were used as raw materials to create hydrogels due to their easily gelation and biological properties. The enhancement of porosity was generated by a fast decompression after keeping the hydrogels in contact with CO 2 . The effect of the processing conditions and type of $\beta$-glucan in the final properties was assessed regarding morphological and mechanical properties. Finally, the ability of these materials to sustainably deliver dexamethasone was evaluated. The scaffolds had good morphology and provided a controlled release, thus being suitable to be used as scaffolds and drug delivery vehicles.

}, keywords = {$\beta$-glucan, Dexamethasone, Drug delivery, Scaffolds, Supercritical hydrogel foaming}, issn = {08968446}, doi = {10.1016/j.supflu.2017.04.006}, author = {Salgado, M. and Rodr{\'\i}guez-Rojo, S. and Reis, R.L. and Cocero, M.J. and Duarte, A.R.C.} } @article {Mano2017, title = {{Production of Electrospun Fast-Dissolving Drug Delivery Systems with Therapeutic Eutectic Systems Encapsulated in Gelatin}}, journal = {AAPS PharmSciTech}, number = {5}, year = {2017}, note = {n/a}, publisher = {AAPS PharmSciTech}, abstract = {

Fast-dissolving delivery systems (FDDS) have received increasing attention in the last years. Oral drug delivery is still the preferred route for the administration of pharmaceutical ingredients. Nevertheless, some patients, e.g. children or elderly people, have difficulties in swallowing solid tablets. In this work, gelatin membranes were produced by electrospinning, containing an encapsulated therapeutic deep-eutectic solvent (THEDES) composed by choline chloride/mandelic acid, in a 1:2 molar ratio. A gelatin solution (30{\%} w/v) with 2{\%} (v/v) of THEDES was used to produce electrospun fibers and the experimental parameters were optimized. Due to the high surface area of polymer fibers, this type of construct has wide applicability. With no cytotoxicity effect, and showing a fast-dissolving release profile in PBS, the gelatin fibers with encapsulated THEDES seem to have promising applications in the development of new drug delivery systems.

}, keywords = {anti-bacterial studies, fast-dissolving drug delivery systems, gelatin, mandelic acid, therapeutic deep-eutectic solvents}, isbn = {1530-9932}, issn = {1530-9932}, doi = {10.1208/s12249-016-0703-z}, url = {http://link.springer.com/10.1208/s12249-016-0703-z}, author = {Mano, Francisca and Martins, Marta and Isabel S{\'a}-Nogueira and Barreiros, Susana and Jo{\~a}o Paulo Borges and Reis, Rui L and Duarte, Ana Rita C and Paiva, Alexandre} } @article {Aroso2016, title = {{Dissolution enhancement of active pharmaceutical ingredients by therapeutic deep eutectic systems}}, journal = {European Journal of Pharmaceutics and Biopharmaceutics}, volume = {98}, year = {2016}, note = {n/a}, pages = {57{\textendash}66}, publisher = {Elsevier B.V.}, abstract = {

A therapeutic deep eutectic system (THEDES) is here defined as a deep eutectic solvent (DES) having an active pharmaceutical ingredient (API) as one of the components. In this work, THEDESs are proposed as enhanced transporters and delivery vehicles for bioactive molecules. THEDESs based on choline chloride (ChCl) or menthol conjugated with three different APIs, namely acetylsalicylic acid (AA), benzoic acid (BA) and phenylacetic acid (PA), were synthesized and characterized for thermal behaviour, structural features, dissolution rate and antibacterial activity. Differential scanning calorimetry and polarized optical microscopy showed that ChCl:PA (1:1), ChCl:AA (1:1), menthol:AA (3:1), menthol:BA (3:1), menthol:PA (2:1) and menthol:PA (3:1) were liquid at room temperature. Dissolution studies in PBS led to increased dissolution rates for the APIs when in the form of THEDES, compared to the API alone. The increase in dissolution rate was particularly noticeable for menthol-based THEDES. Antibacterial activity was assessed using both Gram-positive and Gram-negative model organisms. The results show that all the THEDESs retain the antibacterial activity of the API. Overall, our results highlight the great potential of THEDES as dissolution enhancers in the development of novel and more effective drug delivery systems.

}, keywords = {Drug solubility, Green technologies, Pharmaceutical and biomedical applications, Therapeutic deep eutectic systems}, isbn = {1873-3441 (Electronic)$\backslash$r0939-6411 (Linking)}, issn = {18733441}, doi = {10.1016/j.ejpb.2015.11.002}, url = {http://dx.doi.org/10.1016/j.ejpb.2015.11.002}, author = {Aroso, Ivo M and Silva, Jo{\~a}o C. and Mano, Francisca and Ferreira, Ana S. D. and Dion{\'\i}sio, Madalena and Isabel S{\'a}-Nogueira and Barreiros, Susana and Reis, Rui L and Paiva, Alexandre and Duarte, Ana Rita C} } @article {Barros2016a, title = {{Drug-eluting biodegradable ureteral stent: New approach for urothelial tumors of upper urinary tract cancer}}, journal = {International Journal of Pharmaceutics}, volume = {513}, number = {1-2}, year = {2016}, note = {n/a}, abstract = {

{\textcopyright} 2016 Elsevier B.V. Upper urinary tract urothelial carcinoma (UTUC) accounts for 5{\textendash}10{\%} of urothelial carcinomas and is a disease that has not been widely studied as carcinoma of the bladder. To avoid the problems of conventional therapies, such as the need for frequent drug instillation due to poor drug retention, we developed a biodegradable ureteral stent (BUS) impregnated by supercritical fluid CO 2 (scCO 2 ) with the most commonly used anti-cancer drugs, namely paclitaxel, epirubicin, doxorubicin, and gemcitabine. The release kinetics of anti-cancer therapeutics from drug-eluting stents was measured in artificial urine solution (AUS). The in vitro release showed a faster release in the first 72~h for the four anti-cancer drugs, after this time a plateau was achieved and finally the stent degraded after 9~days. Regarding the amount of impregnated drugs by scCO 2 , gemcitabine showed the highest amount of loading (19.57~$μ$g drug /mg polymer: 2{\%} loaded), while the lowest amount was obtained for paclitaxel (0.067~$μ$g drug /mg polymer : 0.01{\%} loaded). A cancer cell line (T24) was exposed to graded concentrations (0.01{\textendash}2000~ng/ml) of each drugs for 4 and 72~h to determine the sensitivities of the cells to each drug (IC 50 ). The direct and indirect contact study of the anti-cancer biodegradable ureteral stents with the T24 and HUVEC cell lines confirmed the anti-tumoral effect of the BUS impregnated with the four anti-cancer drugs tested, reducing around 75{\%} of the viability of the T24 cell line after 72~h and demonstrating minimal cytotoxic effect on HUVECs.

}, keywords = {Anti-cancer drugs, Biodegradable polymers, supercritical fluid technology, T24 cell line, Upper tract urothelial carcinoma, ureteral stents}, issn = {18733476}, doi = {10.1016/j.ijpharm.2016.08.061}, author = {Barros, A.A. and Browne, S. and Oliveira, C. and Lima, E. and Duarte, A.R.C. and Healy, K.E. and Reis, R.L.} } @article {Silva2016, title = {{Extraction of Collagen/Gelatin from the Marine Demosponge Chondrosia reniformis (Nardo, 1847) Using Water Acidified with Carbon Dioxide - Process Optimization}}, journal = {Industrial and Engineering Chemistry Research}, volume = {55}, number = {25}, year = {2016}, note = {n/a}, pages = {6922{\textendash}6930}, abstract = {

Marine sponges are a rich source of natural bioactive compounds. One of the most abundant valuable products is collagen/gelatin, which presents an interesting alternative source for pharmaceutical and biomedical applications. We have previously proposed an innovative green technology for the extraction of collagen/gelatin from marine sponges based in water acidified with carbon dioxide. In this work, we have optimized the process operating conditions toward high yields and collagen quality as well as to reduce extraction procedure duration and energy consumption. The process extraction efficiency is higher than 50{\%}, corresponding to a yield of approximately 10{\%} of the sponge dry mass, obtained for mild operating conditions of 10 bar and 3 h. The extracted material was characterized by scanning electron microscopy (SEM), rheology, Fourier transformed infrared spectroscopy (FTIR), circular dichroism (CD), amino acid analysis, and SDS-PAGE. The extracts were found to be composed of highly pure mixtures of co...

}, issn = {15205045}, doi = {10.1021/acs.iecr.6b00523}, author = {Silva, Jo{\~a}o C. and Barros, Alexandre A. and Aroso, Ivo M and Fassini, Dario and Silva, Tiago H. and Reis, Rui L and Duarte, Ana Rita C} } @article {Duarte2016, title = {{From honeycomb- to microsphere-patterned surfaces of poly(lactic acid) and a starch-poly(lactic acid) blend via the breath figure method.}}, journal = {Journal of applied biomaterials {\&} functional materials}, volume = {15}, number = {1}, year = {2016}, note = {n/a}, abstract = {

BACKGROUND This study investigated the preparation of ordered patterned surfaces and/or microspheres from a natural-based polymer, using the breath figure and reverse breath figure methods. METHODS Poly(D,L-lactic acid) and starch poly(lactic acid) solutions were precipitated in different conditions - namely, polymer concentration, vapor atmosphere temperature and substrate - to evaluate the effect of these conditions on the morphology of the precipitates obtained. RESULTS The possibility of fine-tuning the properties of the final patterns simply by changing the vapor atmosphere was also demonstrated here using a range of compositions of the vapor phase. Porous films or discrete particles are formed when the differences in surface tension determine the ability of polymer solution to surround water droplets or methanol to surround polymer droplets, respectively. In vitro cytotoxicity was assessed applying a simple standard protocol to evaluate the possibility to use these materials in biomedical applications. Moreover, fluorescent microscopy images showed a good interaction of cells with the material, which were able to adhere on the patterned surfaces after 24 hours in culture. CONCLUSIONS The development of patterned surfaces using the breath figure method was tested in this work for the preparation of both poly(lactic acid) and a blend containing starch and poly(lactic acid). The potential of these films to be used in the biomedical area was confirmed by a preliminary cytotoxicity test and by morphological observation of cell adhesion.

}, keywords = {biomaterials, breath figures, lactic acid, natural polymers, patterns, poly, starch}, isbn = {2280-8000 (Electronic)$\backslash$r2280-8000 (Linking)}, issn = {2280-8000}, doi = {10.5301/jabfm.5000281}, url = {http://www.ncbi.nlm.nih.gov/pubmed/27647384}, author = {Duarte, Ana Rita C and Maniglio, Devid and Sousa, Nuno and Jo{\~a}o F. Mano and Reis, Rui L and Migliaresi, Claudio} } @article {Barros2016, title = {{Hybrid Alginate-Based Cryogels for Life Science Applications}}, journal = {Chemie-Ingenieur-Technik}, volume = {88}, number = {11}, year = {2016}, note = {n/a}, abstract = {

{\textcopyright} 2016 WILEY-VCH Verlag GmbH {\&} Co. KGaA, Weinheim. This work presents a novel route toward porous scaffolds for tissue engineering and regenerative medicine (TERM) applications. Hybrid cryogels with gelatin, gellan gum, carboxymethylcellulose, and lignin were prepared by a two-step process. Textural properties of the cryogels were analyzed by SEM and micro-computed tomography. The results indicated that rapid freezing retained sample shape and yielded macroporous materials. The mechanical properties of the cryogels were characterized in compression mode. Cytotoxicity studies indicated that the hybrid-alginate cryogels did not present cytotoxicity and have the potential to be used in TERM.

}, keywords = {Alginate, Cryogel, Freeze-drying}, issn = {15222640}, doi = {10.1002/cite.201600096}, author = {Barros, A. and Quraishi, S. and Martins, M and Gurikov, P. and Subrahmanyam, R. and Smirnova, I. and Duarte, A.R.C. and Reis, R.L.} } @article {Barros2016b, title = {{In vitro bioactivity studies of ceramic structures isolated from marine sponges}}, journal = {Biomedical Materials (Bristol)}, volume = {11}, number = {4}, year = {2016}, note = {n/a}, abstract = {

{\textcopyright} 2016 IOP Publishing Ltd. In this work, we focused on the potential of bioceramics from different marine sponges - namely Petrosia ficiformis, Agelas oroides and Chondrosia reniformis - for novel biomedical/industrial applications. The bioceramics from these sponges were obtained after calcination at 750 {\textdegree}C for 6 h in a furnace. The morphological characteristics were evaluated by scanning electron microscopy (SEM). The in vitro bioactivity of the bioceramics was evaluated in simulated body fluid (SBF) after 14 and 21 d. Observation of the bioceramics by SEM after immersion in SBF solution, coupled with spectroscopic elemental analysis (EDS), showed that the surface morphology was consistent with a calcium-phosphate (Ca/P) coating, similar to hydroxyapatite crystals (HA). Evaluation of the characteristic peaks of Ca/P crystals by Fourier transform infrared spectroscopy and x-ray diffraction further confirmed the existence of HA. Cytotoxicity studies were carried out with the different ceramics and these were compared with a commercially available Bioglass {\textregistered} . In vitro tests demonstrated that marine bioceramics from these sponges are non-cytotoxic and have the potential to be used as substitutes for synthetic Bioglass {\textregistered} .

}, keywords = {Bioactive glass, Bioactivity, Bioceramics, Hydroxyapatite, Marine sponge}, issn = {1748605X}, doi = {10.1088/1748-6041/11/4/045004}, author = {Barros, A.A. and Aroso, I.M. and Silva, T.H. and Mano, J.F. and Duarte, A.R.C. and Reis, R.L.} } @article {Barros2015a, title = {{Bioresorbable ureteral stents from natural origin polymers}}, journal = {Journal of Biomedical Materials Research - Part B Applied Biomaterials}, volume = {103}, number = {3}, year = {2015}, note = {n/a}, pages = {608{\textendash}617}, abstract = {

In this work, stents were produced from natural origin polysaccharides. Alginate, gellan gum, and a blend of these with gelatin were used to produce hollow tube (stents) following a combination of templated gelation and critical point carbon dioxide drying. Morphological analysis of the surface of the stents was carried out by scanning electron microscopy. Indwelling time, encrustation, and stability of the stents in artificial urine solution was carried out up to 60 days of immersion. In vitro studies carried out with simulated urine demonstrated that the tubes present a high fluid uptake ability, about 1000{\%}. Despite this, the materials are able to maintain their shape and do not present an extensive swelling behavior. The bioresorption profile was observed to be highly dependent on the composition of the stent and it can be tuned. Complete dissolution of the materials may occur between 14 and 60 days. Additionally, no encrustation was observed within the tested timeframe. The ability to resist bacterial adherence was evaluated with Gram-positive Staphylococcus aureus and two Gram-negatives Escherichia coli DH5 alpha and Klebsiella oxytoca. For K. oxytoca, no differences were observed in comparison with a commercial stent (Biosoft((R)) duo, Porges), although, for S. aureus all tested compositions had a higher inhibition of bacterial adhesion compared to the commercial stents. In case of E. coli, the addition of gelatin to the formulations reduced the bacterial adhesion in a highly significant manner compared to the commercial stents. The stents produced by the developed technology fulfill the requirements for ureteral stents and will contribute in the development of biocompatible and bioresorbable urinary stents.

}, keywords = {aerogel/hydrogel, bioresorbable polymers, kidney stones, natural polymers, supercritical fluid technology, ureteral stents}, isbn = {1552-4973}, issn = {15524981}, doi = {10.1002/jbm.b.33237}, author = {Barros, Alexandre A. and Rita, A N A and Duarte, A.R.C. and Pires, Ricardo A. and Sampaio-Marques, Bel{\'e}m and Ludovico, Paula and Lima, Estev{\~a}o and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Aroso2015, title = {{Cork processing with supercritical carbon dioxide: Impregnation and sorption studies}}, journal = {Journal of Supercritical Fluids}, volume = {104}, year = {2015}, note = {n/a}, pages = {251{\textendash}258}, publisher = {Elsevier B.V.}, abstract = {

Abstract The present study relates to the use of supercritical carbon dioxide (SCCO{\textless}inf{\textgreater}2{\textless}/inf{\textgreater}) to modify the properties of cork by incorporation of new molecules. The impact of SCCO{\textless}inf{\textgreater}2{\textless}/inf{\textgreater}processing on the morphology and on the mechanical properties was found to be negligible.The impregnation of disperse blue 14 (blue dye) on cubic shaped cork samples of 5 mm occurs progressively,is dependent of the processing conditions and of the presence of lenticels and growth rings. The impregnation of the samples bulk was achieved with processing at 10 MPa and 313 K for 16 h. The solubility and sorption of SCCO{\textless}inf{\textgreater}2{\textless}/inf{\textgreater} in the cork matrix was measured using circular discs and the diffusion coefficients calculated to be on the order of 10{\textless}sup{\textgreater}-8{\textless}/sup{\textgreater} cm{\textless}sup{\textgreater}2{\textless}/sup{\textgreater}/s, the same order as for wood materials. This work demonstrates the feasibility of supercritical fluid technology to impart new features to cork, which may lead to innovative architectural, outdoor and industrial applications.

}, keywords = {Carbon dioxide, cork, Impregnation, Natural matrices, sorption, Supercritical fluids}, issn = {08968446}, doi = {10.1016/j.supflu.2015.06.024}, url = {http://dx.doi.org/10.1016/j.supflu.2015.06.024}, author = {Aroso, Ivo M and Duarte, Ana Rita C and Pires, Ricardo R. and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Aroso2015a, title = {{Design of controlled release systems for THEDES - Therapeutic deep eutectic solvents, using supercritical fluid technology}}, journal = {International Journal of Pharmaceutics}, volume = {492}, number = {1-2}, year = {2015}, note = {n/a}, abstract = {

{\textcopyright} 2015 Elsevier B.V. Abstract Deep eutectic solvents (DES) can be formed by bioactive compounds or pharmaceutical ingredients. A therapeutic DES (THEDES) based on ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), and menthol was synthesized and its thermal behavior was analyzed by differential scanning calorimetry (DSC). A controlled drug delivery system was developed by impregnating a starch:poly-{\"I}$μ$-caprolactone polymeric blend (SPCL 30:70) with the menthol:ibuprofen THEDES in different ratios (10 and 20 wt{\%}), after supercritical fluid sintering at 20 MPa and 50 {\textdegree}C. The morphological characterization of SPCL matrices impregnated with THEDES was performed by scanning electron microscopy (SEM) and micro-computed tomography (micro-CT). Drug release studies were carried out in a phosphate buffered saline. The results obtained provide important clues for the development of carriers for the sustainable delivery of bioactive compounds.

}, keywords = {Biodegradable polymers, Drug delivery systems, Ibuprofen, supercritical carbon dioxide, Therapeutic deep eutectic solvents}, issn = {18733476}, doi = {10.1016/j.ijpharm.2015.06.038}, author = {Aroso, I.M. and Craveiro, R. and Rocha, {\^A}. and M. Dion{\'\i}sio and S. Barreiros and Reis, R.L. and Paiva, A. and Duarte, A.R.C.} } @article {Barros2015b, title = {{Ketoprofen-eluting biodegradable ureteral stents by CO{\textless}inf{\textgreater}2{\textless}/inf{\textgreater}impregnation: In vitro study}}, journal = {International Journal of Pharmaceutics}, volume = {495}, number = {2}, year = {2015}, note = {n/a}, abstract = {

{\textcopyright} 2015 Elsevier B.V. Ureteral stents are indispensable tools in urologic practice. The main complications associated with ureteral stents are dislocation, infection, pain and encrustation. Biodegradable ureteral stents are one of the most attractive designs with the potential to eliminate several complications associated with the stenting procedure. In this work we hypothesize the impregnation of ketoprofen, by CO 2 -impregnation in a patented biodegradable ureteral stent previously developed in our group. The biodegradable ureteral stents with each formulation: alginate-based, gellan gum-based were impregnated with ketoprofen and the impregnation conditions tested were 100 bar, 2 h and three different temperatures (35 {\textdegree}C, 40{\textdegree}C and 50{\textdegree}C). The impregnation was confirmed by FTIR and DSC demonstrated the amorphization of the drug upon impregnation. The in vitro elution profile in artificial urine solution (AUS) during degradation of a biodegradable ureteral stent loaded with ketoprofen was evaluated. According to the kinetics results these systems have shown to be very promising for the release ketoprofen in the first 72 h, which is the necessary time for anti-inflammatory delivery after the surgical procedure. The in vitro release studied revealed an influence of the temperature on the impregnation yield, with a higher impregnation yield at 40{\textdegree}C. Higher yields were also obtained for gellan gum-based stents. The non-cytotoxicity characteristic of the developed ketoprofen-eluting biodegradable ureteral stents was evaluated in L929 cell line by MTS assay which demonstrated the feasibility of this product as a medical device.

}, keywords = {Biodegradable polymers, Hydrogel, Ketoprofen-eluting, kidney stones, natural polymers, supercritical fluid technology, ureteral stents}, issn = {18733476}, doi = {10.1016/j.ijpharm.2015.08.040}, author = {Barros, A.A. and Oliveira, C. and Reis, R.L. and Lima, E. and Duarte, A.R.C.} } @article {Quraishi2015, title = {{Novel non-cytotoxic alginate{\textendash}lignin hybrid aerogels as scaffolds for tissue engineering}}, journal = {Journal of Supercritical Fluids}, volume = {105}, year = {2015}, note = {n/a}, pages = {1{\textendash}8}, publisher = {Elsevier B.V.}, abstract = {

This paper presents a novel approach toward the production of hybrid alginate{\textendash}lignin aerogels. The key idea of the approach is to employ pressurized carbon dioxide for gelation. Exposure of alginate and lignin aqueous alkali solution containing calcium carbonate to CO2at 4.5~MPa resulted in a hydrogel formation. Various lignin and CaCO3concentrations were studied. Stable hydrogels could be formed up to 2:1 (w/w) alginate-to-lignin ratio (1.5~wt{\%} overall biopolymer concentration). Upon substitution of water with ethanol, gels were dried in supercritical CO2to produce aerogels. Aerogels with bulk density in the range 0.03{\textendash}0.07~g/cm3, surface area up to 564~m2/g and pore volume up to 7.2~cm3/g were obtained. To introduce macroporosity, the CO2induced gelation was supplemented with rapid depressurization (foaming process). Macroporosity up to 31.3~{\textpm}~1.9{\%} with interconnectivity up to 33.2~{\textpm}~8.3{\%} could be achieved at depressurization rate of 3~MPa/min as assessed by micro-CT. Young{\textquoteright}s modulus of alginate{\textendash}lignin aerogels was measured in both dry and wet states. Cell studies revealed that alginate{\textendash}lignin aerogels are non-cytotoxic and feature good cell adhesion making them attractive candidates for a wide range of applications including tissue engineering and regenerative medicine.

}, keywords = {Alginate, biomaterials, Lignin, Scaffolds, Supercritical, tissue engineering}, isbn = {4042878407}, issn = {08968446}, doi = {10.1016/j.supflu.2014.12.026}, url = {http://dx.doi.org/10.1016/j.supflu.2014.12.026}, author = {Quraishi, Sakeena and Martins, Marta and Barros, Alexandre A. and Gurikov, Pavel and Raman, S. P. and Smirnova, Irina and Duarte, Ana Rita C and Reis, Rui L} } @article {Martins2015, title = {{Preparation of macroporous alginate-based aerogels for biomedical applications}}, journal = {Journal of Supercritical Fluids}, year = {2015}, note = {n/a}, publisher = {Elsevier B.V.}, abstract = {

Aerogels are a special class of ultra-light porous materials with growing interest in biomedical applications due to their open pore structure and high surface area. However, they usually lack macroporosity, while mesoporosity is typically high. In this work, carbon dioxide induced gelation followed by expansion of the dissolved CO{\textless}inf{\textgreater}2{\textless}/inf{\textgreater} was performed to produce hybrid calcium-crosslinked alginate-starch hydrogels with dual meso- and macroporosity. The hydrogels were subjected to solvent exchange and supercritical drying to obtain aerogels. Significant increase in macroporosity from 2 to 25{\%} was achieved by increasing expansion rate from 0.1 to 30 bar/min with retaining mesoporosity (BET surface and BJH pore volume in the range 183-544m{\textless}sup{\textgreater}2{\textless}/sup{\textgreater}/g and 2.0-6.8cm{\textless}sup{\textgreater}3{\textless}/sup{\textgreater}/g, respectively). In vitro bioactivity studies showed that the alginate-starch aerogels are bioactive, i.e. they form hydroxyapatite crystals when immersed in a simulated body fluid solution. Bioactivity is attributed to the presence of calcium in the matrix. The assessment of the biological performance showed that the aerogels do not present a cytotoxic effect and the cells are able to colonize and grow on their surface. Results presented in this work provide a good indication of the potential of the alginate-starch aerogels in biomedical applications, particularly for bone regeneration.

}, keywords = {Aerogels, Alginate, CO{\textless}inf{\textgreater}2{\textless}/inf{\textgreater} induced gelation, starch, Supercritical fluids, tissue engineering}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2015.05.010}, url = {http://dx.doi.org/10.1016/j.supflu.2015.05.010}, author = {Martins, Marta and Barros, Alexandre A. and Quraishi, Sakeena and Gurikov, Pavel and Raman, S. P. and Smirnova, Irina and Duarte, Ana Rita C and Reis, Rui L} } @article {Barros2015, title = {{Water and carbon dioxide: Green solvents for the extraction of collagen/gelatin from marine sponges}}, journal = {ACS Sustainable Chemistry and Engineering}, volume = {3}, number = {2}, year = {2015}, note = {n/a}, pages = {254{\textendash}260}, abstract = {

Marine sponges are extremely rich in natural products and are considered a promising biological resource. The major objective of this work is to couple a green extraction process with a natural origin raw material to obtain sponge origin collagen/gelatin for biomedical applications. Marine sponge collagen has unique physicochemical properties, but its application is hindered by the lack of availability due to inefficient extraction methodologies. Traditional extraction methods are time consuming as they involve several operating steps and large amounts of solvents. In this work, we propose a new extraction methodology under mild operating conditions in which water is acidified with carbon dioxide (CO2) to promote the extraction of collagen/gelatin from different marine sponge species. An extraction yield of approximately 50{\%} of collagen/gelatin was achieved. The results of Fourier transformed infrared spectroscopy (FTIR), circular dichroism (CD), and differential scanning calorimetry (DSC) spectra suggest a mixture of collagen/gelatin with high purity, and the analysis of the amino acid composition has shown similarities with collagen from other marine sources. Additionally, in vitro cytotoxicity studies did not demonstrate any toxicity effects for three of the extracts.

}, keywords = {Carbon dioxide, Collagen, Extraction, gelatin, Green solvents, Marine sponges, Natural products, water}, issn = {21680485}, doi = {10.1021/sc500621z}, author = {Barros, Alexandre A. and Aroso, Ivo M and Silva, Tiago H. and Jo{\~a}o F. Mano and Duarte, Ana Rita C and Reis, Rui L} } @article {11971, title = {pubs.acs.org/acssce}, volume = {2}, number = {5}, year = {2014}, note = {n/a}, pages = {2014}, abstract = {n/a} } @article {Martins2014, title = {{Enhanced performance of supercritical fluid foaming of natural-based polymers by deep eutectic solvents}}, journal = {AIChE Journal}, volume = {60}, number = {11}, year = {2014}, note = {n/a}, abstract = {

{\textcopyright} 2014 American Institute of Chemical Engineers. Significance: Natural deep eutectic solvents (NADES) are defined as a mixture of two or more solid or liquid components, which at a particular composition present a high melting point depression becoming liquids at room temperature. NADES are constituted by natural molecules and fully represent the green chemistry principles. For these reasons, the authors believe that the submitted manuscript is a highly valuable contribution to the field of green chemistry and chemical engineering. For the first time, the possibility to use NADES as enhancers of supercritical fluid technology is revealed.

}, keywords = {biomaterials, Green engineering, Polymer processing, Supercritical processes}, issn = {15475905}, doi = {10.1002/aic.14607}, author = {Martins, M and Aroso, I.M. and Reis, R.L. and Duarte, A.R.C. and Craveiro, R. and Paiva, A.} } @article {Duarte2014, title = {{Micro fluidic Production of Perfluorocarbon-Alginate Core - Shell Microparticles for Ultrasound Therapeutic Applications}}, journal = {Langmuir}, year = {2014}, note = {n/a}, abstract = {n/a}, isbn = {0743-7463}, doi = {10.1021/la502822}, author = {Duarte, Ana Rita C and Mano, F and Reis, Rui L and Jensen, Klavs F} } @article {Silva2014, title = {{Nanostructured Hollow Tubes Based on Chitosan and Alginate Multilayers}}, journal = {Advanced Healthcare Materials}, volume = {3}, number = {3}, year = {2014}, note = {n/a}, pages = {433{\textendash}440}, abstract = {

The design and production of structures with nanometer-sized polymer films based on layer-by-layer (LbL) are of particular interest for tissue engineering since they allow the precise control of physical and biochemical cues of implantable devices. In this work, a method is developed for the preparation of nanostructured hollow multilayers tubes combining LbL and template leaching. The aim is to produce hollow tubes based on polyelectrolyte multilayer films with tuned physical-chemical properties and study their effects on cell behavior. The final tubular structures are characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), microscopy, swelling, and mechanical tests, including dynamic mechanical analysis (DMA) in physiological simulated conditions. It is found that more robust films could be produced upon chemical cross-linking with genipin. In particular, the mechanical properties confirms the viscoelastic properties and a storage and young modulus about two times higher. The water uptake decreases from about 390{\%} to 110{\%} after the cross-linking. The biological performance is assessed in terms of cell adhesion, viability, and proliferation. The results obtained with the cross-linked tubes demonstrate that these are more suitable structures for cell adhesion and spreading. The results suggest the potential of these structures to boost the development of innovative tubular structures for tissue engineering approaches.

}, keywords = {Alginate, chitosan, Layer-by-layer, tissue engineering, Tubular structures}, isbn = {2192-2640 (Print)$\backslash$r2192-2640 (Linking)}, issn = {21922659}, doi = {10.1002/adhm.201300265}, author = {Silva, Joana M and Duarte, Ana Rita C and Cust{\'o}dio, Catarina A. and Sher, Praveen and Neto, Ana I. and Pinho, Ant{\'o}nio C M and Fonseca, Jaime and Reis, Rui L and Jo{\~a}o F. Mano} } @article {Paiva2014, title = {{Natural deep eutectic solvents - Solvents for the 21st century}}, journal = {ACS Sustainable Chemistry and Engineering}, volume = {2}, number = {5}, year = {2014}, note = {n/a}, abstract = {

Green technology actively seeks new solvents to replace common organic solvents that present inherent toxicity and have high volatility, leading to evaporation of volatile organic compounds to the atmosphere. Over the past two decades, ionic liquids (ILs) have gained enormous attention from the scientific community, and the number of reported articles in the literature has grown exponentially. Nevertheless, IL "greenness" is often challenged, mainly due to their poor biodegradability, biocompatibility, and sustainability. An alternative to ILs are deep eutectic solvents (DES). Deep eutectic solvents are defined as a mixture of two or more components, which may be solid or liquid and that at a particular composition present a high melting point depression becoming liquids at room temperature. When the compounds that constitute the DES are primary metabolites, namely, aminoacids, organic acids, sugars, or choline derivatives, the DES are so called natural deep eutectic solvents (NADES). NADES fully represent green chemistry principles. Can natural deep eutectic solvents be foreseen as the next generation solvents and can a similar path to ionic liquids be outlined? The current state of the art concerning the advances made on these solvents in the past few years is reviewed in this paper, which is more than an overview on the different applications for which they have been suggested, particularly, biocatalysis, electrochemistry, and extraction of new data. Citotoxicity of different NADES was evaluated and compared to conventional imidazolium-based ionic liquids, and hints at the extraction of phenolic compounds from green coffee beans and on the foaming effect of NADES are revealed. Future perspectives on the major directions toward which the research on NADES is envisaged are here discussed, and these comprised undoubtedly a wide range of chemically related subjects. {\textcopyright} 2014 American Chemical Society.

}, keywords = {Choline chloride, Green chemistry, ionic liquids, Natural deep eutectic solvents, Physical-chemistry properties}, issn = {21680485}, doi = {10.1021/sc500096j}, author = {Paiva, A. and Craveiro, R. and Aroso, I. and Martins, M and Reis, R.L. and Duarte, A.R.C.} } @article {Babo2014, title = {{Platelet lysate membranes as new autologous templates for tissue engineering applications}}, journal = {Inflammation and Regeneration}, volume = {34}, number = {1}, year = {2014}, note = {n/a}, pages = {033{\textendash}044}, abstract = {n/a}, issn = {1880-9693}, doi = {10.2492/inflammregen.34.033}, url = {http://jlc.jst.go.jp/DN/JST.JSTAGE/inflammregen/34.033?lang=en{\&}from=CrossRef{\&}type=abstract}, author = {Babo, Pedro and Santo, V{\^{}}|{\^{}}iacute;tor E and Duarte, Ana Rita C and Correia, Cl{\^{}}|{\^{}}aacute;udia and Costa, Marta H G and Mano, Jo{\^{}}|{\^{}}atilde;o F and Reis, Rui L and Gomes, Manuela E.} } @article {Craveiro2014, title = {{Starch-based polymer-IL composites formed by compression moulding and supercritical fluid foaming for self-supported conductive materials}}, journal = {RSC Advances}, volume = {4}, number = {33}, year = {2014}, note = {n/a}, abstract = {

In this work, blends of starch and poly-$ε$-caprolactone (PCL) doped with different concentrations of 1-butyl-3-methylimidazolium acetate ([BMIM]Ac) or 1-butyl-3-methylimidazolium chloride ([BMIM] Cl) were studied. The blends were characterized by mechanical analysis, infra-red spectroscopy (FTIR), differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS), evaluating the IL doping effect. The samples were subjected to supercritical carbon dioxide foaming and the morphology of the structures was assessed. DSC shows a single glass transition and melting endotherm for foamed and unfoamed samples, having no effect upon IL doping, and DRS shows increased molecular mobility for blends with higher IL concentrations, and some hindrance for lower ones. The conductivity for SPCL doped with 30{\%} [BMIM] Cl, before and after foaming, is comparable to the conductivity of the IL but exhibits more stable conductivity values, opening doors for applications as self-supported conductive materials. {\textcopyright} 2014 the Partner Organisations.

}, issn = {20462069}, doi = {10.1039/c4ra01424c}, author = {Craveiro, R. and Martins, M and Santos, G.B. and Correia, N. and M. Dion{\'\i}sio and S. Barreiros and Duarte, A.R.C. and Reis, R.L. and Paiva, A.} } @article {Martins2014a, title = {{Supercritical fluid processing of natural based polymers doped with ionic liquids}}, journal = {Chemical Engineering Journal}, volume = {241}, year = {2014}, note = {n/a}, abstract = {

Some approaches have been developed in our group to investigate the role of novel ionic liquids as process and property modifiers of natural-based polymers. In our previous work, we proposed the use of ionic liquids as plasticizing agents for the creation of porous structures from a semi-crystalline natural-based polymer. The current work intended to complement the previous studies, evaluating the ability of ionic liquid (IL) to plasticize polymers such as blends of starch-poly-lactic acid (SPLA) and its effect on supercritical fluid foaming process (SCF) and providing more insights on the mechanisms involved. For this purpose, blends of starch with poly (lactic) acid, with different ratios of starch and poly-lactic acid of 50:50 and 30:70 were modified and processed using 1-butyl-3-methylimidazolium chloride ([bmim]Cl). Supercritical fluid foaming was studied at different soaking times (1, 3 and 6h) using carbon dioxide at 20.0MPa and 40{\textdegree}C. The blends were characterized by different techniques, such as infra-red spectroscopy, differential scanning calorimetry and compression and tensile mechanical analysis. The morphology of the foamed structures was analyzed by scanning electron microscopy and micro-computed tomography. The results suggest that after 3h of soaking time an equilibrium state of carbon dioxide into the bulk samples is attained, yielding structures with 6{\%} and 15{\%} of porosity, for SPLA70 and SPLA50 respectively. The solubility of carbon dioxide within the matrices was studied for the same conditions and the results demonstrate a higher sorption degree in the samples doped with ionic liquid. Sorption and desorption diffusion coefficients of supercritical CO 2 in the SPLA matrix were determined for the raw polymer and for the SPLA doped with [bmim]Cl. It was found that the lower desorption diffusion coefficients are related with the higher porosity obtained by the foaming process. {\textcopyright} 2013.

}, keywords = {Carbon dioxide, ionic liquids, Poly (lactic acid), Polymer processing, starch, Supercritical fluid foaming}, issn = {13858947}, doi = {10.1016/j.cej.2013.11.080}, author = {Martins, M and Craveiro, R. and Paiva, A. and Duarte, A.R.C. and Reis, R.L.} } @article {Barros2014, title = {{Surface modification of silica-based marine sponge bioceramics induce hydroxyapatite formation}}, journal = {Crystal Growth and Design}, volume = {14}, number = {9}, year = {2014}, note = {n/a}, pages = {4545{\textendash}4552}, abstract = {

Marine biomaterials are a new emerging area of research with significant applications. Recently, researchers are dedicating considerable attention to marine-sponge biomaterials for various applications. We have focused on the potential of biosilica from Petrosia ficidormis for novel biomedical/industrial applications. A bioceramic structure from this sponge was obtained after calcination at 750 {\textdegree}C for 6 h in a furnace. The morphological characteristics of the three-dimensional architecture were evaluated by scanning electron microscopy (SEM) and microcomputed tomography, revealing a highly porous and interconnected structure. The skeleton of P. ficidormis is a siliceous matrix composed of SiO2, which does not present inherent bioactivity. Induction of bioactivity was attained by subjecting the bioceramics structure to an alkaline treatment (2M KOH) and acidic treatment (2M HCl) for 1 and 3 h. In vitro bioactivity of the bioceramics structure was evaluated in simulated body fluid (SBF), after 7 and 14 days. Observation of the structures by SEM, coupled with spectroscopic elemental analysis (EDS), has shown that the surface morphology presented a calcium-phosphate CaP coating, similar to hydroxyapatite (HA). The determination of the Ca/P ratio, together with the evaluation of the characteristic peaks of HA by infrared spectroscopy and X-ray diffraction, have proven the existence of HA. In vitro biological performance of the structures was evaluated using an osteoblast cell line, and the acidic treatment has shown to be the most effective treatment. Cells were seeded on bioceramics structures and their morphology; viability and growth were evaluated by SEM, MTS assay, and DNA quantification, respectively, demonstrating that cells are able to grow and colonize the bioceramic structures. {\textcopyright} 2014 American Chemical Society.

}, issn = {15287505}, doi = {10.1021/cg500654u}, author = {Barros, Alexandre A. and Aroso, Ivo M and Silva, Tiago H. and Jo{\~a}o F. Mano and Duarte, Ana Rita C and Reis, Rui L} } @article {Silva2014a, title = {{Tailored freestanding multilayered membranes based on chitosan and alginate}}, journal = {Biomacromolecules}, volume = {15}, number = {10}, year = {2014}, note = {n/a}, abstract = {

{\textcopyright} 2014 American Chemical Society. Engineering metabolically demanding tissues requires the supply of nutrients, oxygen, and removal of metabolic byproducts, as well as adequate mechanical properties. In this work, we propose the development of chitosan (CHIT)/alginate (ALG) freestanding membranes fabricated by layer-by-layer (LbL) assembly. CHIT/ALG membranes were cross-linked with genipin at a concentration of 1 mg{\textperiodcentered}mL {\textless} sup {\textgreater} -1 {\textless} /sup {\textgreater} or 5 mg{\textperiodcentered}mL {\textless} sup {\textgreater} -1 {\textless} /sup {\textgreater} . Mass transport properties of glucose and oxygen were evaluated on the freestanding membranes. The diffusion of glucose and oxygen decreases with increasing cross-linking concentration. Mechanical properties were also evaluated in physiological-simulated conditions. Increasing cross-linking density leads to an increase of storage modulus, Young modulus, and ultimate tensile strength, but to a decrease in the maximum hydrostatic pressure. The in vitro biological performance demonstrates that cross-linked films are more favorable for cell adhesion. This work demonstrates the versatility and feasibility of LbL assembly to generate nanostructured constructs with tunable permeability, mechanical, and biological properties.

}, issn = {15264602}, doi = {10.1021/bm501156v}, author = {Silva, J.M. and Duarte, A.R.C. and Caridade, S.G. and Picart, C. and Reis, R.L. and Mano, J.F.} } @article {Silva2013a, title = {{Alternative methodology for chitin-hydroxyapatite composites using ionic liquids and supercritical fluid technology}}, journal = {Journal of Bioactive and Compatible Polymers}, volume = {28}, number = {5}, year = {2013}, note = {n/a}, abstract = {

An alternative, green method was used to develop chitin-based biocomposite (ChHA) materials by an integrated strategy using ionic liquids, supercritical fluid drying, and salt leaching. ChHA matrices were produced by dissolving chitin in 1-butyl-methylimidazolium acetate along with salt and/or hydroxyapatite particles and then subsequent drying. The ChHA composite formed had a heterogeneous porous microstructure with 65{\%}-85{\%} porosity and pore sizes in the range of 100-300 $μ$m. The hydroxyapatite was found to be well distributed within the composite structures and had a positive effect in the viability and proliferation of osteoblast-like cells, in vitro. Our findings indicate that these ChHA matrices have potential applications in bone tissue engineering. {\textcopyright} The Author(s) 2013.

}, keywords = {Chitin, Composites, controlled pore sizes, Hydroxyapatite, ionic liquids, salt leaching, scaffold pores sizing, supercritical fluid technology}, issn = {08839115}, doi = {10.1177/0883911513501595}, author = {Silva, S.S. and Duarte, A.R.C. and Oliveira, J.M. and Mano, J.F. and Reis, R.L.} } @article {Silva2013, title = {{Design and functionalization of chitin-based microsphere scaffolds}}, journal = {Green Chemistry}, volume = {15}, number = {11}, year = {2013}, note = {n/a}, pages = {3252}, abstract = {

Chitin agglomerated scaffolds were produced and functionalized using the green chemistry principles and clean technologies. Such combination enabled the functionalization of chitin microparticles prepared through dissolution of the polymer in ionic liquids, followed by of the application of a sol-gel method. Finally, the 3D constructs were moulded and dried using a supercritical assisted agglomeration method. Structural and morphological characterization is presented using scanning electronic microscopy (SEM) and micro-computed tomography ([small micro]-CT). An evaluation of the bioactive behavior of the matrices was made by immersing them in simulated body fluid (SBF) for up to 21 days. The potential of such matrices as drug delivery systems was evaluated after the incorporation of dexamethasone into the matrices during drying in supercritical assisted agglomeration. The findings suggested that the morphological features such as porosity, interconnectivity and pore size distribution of the matrices can be tunned by changing particle size, chitin concentration and the pressure applied during moulding. Chitin microspheres were modified by siloxane and silanol groups, providing a bioactive behavior; the apatite formation was shown to be dependent on the amount and arrangement of silanol groups. Furthermore, in vitro drug release studies showed that dexamethasone was sustainably released. All findings suggest that this strategy is a feasible and advantageous process to obtain chitin-based 3D structures with both functional and structural characteristics that make then suitable for regenerative medicine applications.

}, isbn = {1463-9262}, issn = {1463-9262}, doi = {10.1039/c3gc41060a}, url = {http://xlink.rsc.org/?DOI=c3gc41060a}, author = {Silva, Simone S and Duarte, Ana Rita C and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Fernandes-Silva2013, title = {{Porous hydrogels from shark skin collagen crosslinked under dense carbon dioxide atmosphere}}, journal = {Macromolecular Bioscience}, volume = {13}, number = {11}, year = {2013}, note = {n/a}, abstract = {

The possibility to fabricate marine collagen porous structures crosslinked with genipin under high pressure carbon dioxide is investigated. Collagen from shark skin is used to prepare pre-scaffolds by freeze-drying. The poor stability of the structures and low mechanical properties require crosslinking of the structures. Under dense CO 2 atmosphere, crosslinking of collagen pre-scaffolds is allowed for 16 h. Additionally, the hydrogels are foamed and the scaffolds obtained present a highly porous structure. In vitro cell culture tests performed with a chondrocyte-like cell line show good cell adherence and proliferation, which is a strong indication of the potential of these scaffolds to be used in tissue cartilage tissue engineering. The development of an optimized processing technique for the preparation of stable structures from marine origin collagen is described. The samples are processed under a dense carbon dioxide atmosphere that promotes crosslinking and enhances the morphology of the 3D architectures obtained. {\textcopyright} 2013 WILEY-VCH Verlag GmbH {\&} Co. KGaA, Weinheim.

}, keywords = {Collagen, hydrogels, marine biotechnology, Supercritical fluids, tissue engineering}, issn = {16165187}, doi = {10.1002/mabi.201300228}, author = {Fernandes-Silva, S. and Moreira-Silva, J. and Silva, T.H. and Perez-Martin, R.I. and Sotelo, C.G. and Mano, J.F. and Duarte, A.R.C. and Reis, R.L.} } @article {Engineering2013, title = {{PT 106220}}, volume = {106220}, number = {11}, year = {2013}, note = {n/a}, abstract = {n/a}, author = {Engineering, Tissue and Based, Cell and Gualtar, Campus D E and Manuela, Maria and Gomes, Estima and Rita, A N A and Duarte, Cruz and Fornecer, Sentido D E and Estrutura, U M A and Interconectada, Porosa E and Crescimento, D E Suporte A O} } @article {Engineering2013, title = {{PT 106220}}, volume = {106220}, number = {11}, year = {2013}, note = {n/a}, abstract = {n/a}, author = {Engineering, Tissue and Based, Cell and Gualtar, Campus D E and Manuela, Maria and Gomes, Estima and Rita, A N A and Duarte, Cruz and Fornecer, Sentido D E and Estrutura, U M A and Interconectada, Porosa E and Crescimento, D E Suporte A O} } @article {Duarte2013, title = {{Unleashing the potential of supercritical fluids for polymer processing in tissue engineering and regenerative medicine}}, journal = {Journal of Supercritical Fluids}, volume = {79}, year = {2013}, note = {n/a}, pages = {177{\textendash}185}, publisher = {Elsevier B.V.}, abstract = {

One of the major scientific challenges that tissue engineering and regenerative medicine (TERM) faces to move from benchtop to bedside regards biomaterials development, despite the latest advances in polymer processing technologies. A variety of scaffolds processing techniques have been developed and include solvent casting and particles leaching, compression molding and particle leaching, thermally induced phase separation, rapid prototyping, among others. Supercritical fluids appear as an interesting alternative to the conventional methods for processing biopolymers as they do not require the use of large amounts of organic solvents and the processes can be conducted at mild temperatures. However, this processing technique has only recently started to receive more attention from researchers. Different processing methods based on the use of supercritical carbon dioxide have been proposed for the creation of novel architectures based on natural and synthetic polymers and these will be unleashed in this paper. {\textcopyright} 2013 Elsevier B.V. All rights reserved.

}, keywords = {biomaterials, Foaming, natural polymers, Phase inversion, Scaffolds, Supercritical fluid drying, Supercritical fluids, tissue engineering}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2013.01.004}, url = {http://dx.doi.org/10.1016/j.supflu.2013.01.004}, author = {Duarte, Ana Rita C and Santo, Vitor E. and Alves, Anabela and Silva, Simone S and Moreira-Silva, Joana and Silva, Tiago H. and Marques, Alexandra P. and Sousa, Rui A. and Gomes, Manuela E. and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Duarte2013a, title = {{Unleashing the potential of supercritical fluids for polymer processing in tissue engineering and regenerative medicine}}, journal = {Journal of Supercritical Fluids}, volume = {79}, year = {2013}, note = {n/a}, pages = {177{\textendash}185}, publisher = {Elsevier B.V.}, abstract = {

One of the major scientific challenges that tissue engineering and regenerative medicine (TERM) faces to move from benchtop to bedside regards biomaterials development, despite the latest advances in polymer processing technologies. A variety of scaffolds processing techniques have been developed and include solvent casting and particles leaching, compression molding and particle leaching, thermally induced phase separation, rapid prototyping, among others. Supercritical fluids appear as an interesting alternative to the conventional methods for processing biopolymers as they do not require the use of large amounts of organic solvents and the processes can be conducted at mild temperatures. However, this processing technique has only recently started to receive more attention from researchers. Different processing methods based on the use of supercritical carbon dioxide have been proposed for the creation of novel architectures based on natural and synthetic polymers and these will be unleashed in this paper. {\textcopyright} 2013 Elsevier B.V. All rights reserved.

}, keywords = {biomaterials, Foaming, natural polymers, Phase inversion, Scaffolds, Supercritical fluid drying, Supercritical fluids, tissue engineering}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2013.01.004}, url = {http://dx.doi.org/10.1016/j.supflu.2013.01.004}, author = {Duarte, Ana Rita C and Santo, Vitor E. and Alves, Anabela and Silva, Simone S and Moreira-Silva, Joana and Silva, Tiago H. and Marques, Alexandra P. and Sousa, Rui A. and Gomes, Manuela E. and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Correia2012, title = {{Dynamic culturing of cartilage tissue: The significance of hydrostatic pressure}}, journal = {Tissue Engineering - Part A}, volume = {18}, number = {19-20}, year = {2012}, note = {n/a}, abstract = {

Human articular cartilage functions under a wide range of mechanical loads in synovial joints, where hydrostatic pressure (HP) is the prevalent actuating force. We hypothesized that the formation of engineered cartilage can be augmented by applying such physiologic stimuli to chondrogenic cells or stem cells, cultured in hydrogels, using custom-designed HP bioreactors. To test this hypothesis, we investigated the effects of distinct HP regimens on cartilage formation in vitro by either human nasal chondrocytes (HNCs) or human adipose stem cells (hASCs) encapsulated in gellan gum (GG) hydrogels. To this end, we varied the frequency of low HP, by applying pulsatile hydrostatic pressure or a steady hydrostatic pressure load to HNC-GG constructs over a period of 3 weeks, and evaluated their effects on cartilage tissue-engineering outcomes. HNCs (10{\texttimes}10 6 cells/mL) were encapsulated in GG hydrogels (1.5{\%}) and cultured in a chondrogenic medium under three regimens for 3 weeks: (1) 0.4 MPa Pulsatile HP; (2) 0.4 MPa Steady HP; and (3) Static. Subsequently, we applied the pulsatile regimen to hASC-GG constructs and varied the amplitude of loading, by generating both low (0.4 MPa) and physiologic (5 MPa) HP levels. hASCs (10{\texttimes}10 6 cells/mL) were encapsulated in GG hydrogels (1.5{\%}) and cultured in a chondrogenic medium under three regimens for 4 weeks: (1) 0.4 MPa Pulsatile HP; (2) 5 MPa Pulsatile HP; and (3) Static. In the HNC study, the best tissue development was achieved by the pulsatile HP regimen, whereas in the hASC study, greater chondrogenic differentiation and matrix deposition were obtained for physiologic loading, as evidenced by gene expression of aggrecan, collagen type II, and sox-9; metachromatic staining of cartilage extracellular matrix; and immunolocalization of collagens. We thus propose that both HNCs and hASCs detect and respond to physical forces, thus resembling joint loading, by enhancing cartilage tissue development in a frequency- and amplitude-dependant manner. {\textcopyright} Copyright 2012, Mary Ann Liebert, Inc.

}, issn = {1937335X}, doi = {10.1089/ten.tea.2012.0083}, author = {Correia, C and Pereira, A.L. and Duarte, A.R.C. and Frias, A.M. and Pedro, A.J. and Oliveira, J.T. and Sousa, R.A. and Reis, R.L.} } @article {Santo2012, title = {{Enhancement of osteogenic differentiation of human adipose derived stem cells by the controlled release of platelet lysates from hybrid scaffolds produced by supercritical fluid foaming}}, journal = {Journal of Controlled Release}, volume = {162}, number = {1}, year = {2012}, note = {n/a}, abstract = {

A new generation of scaffolds capable of acting not only as support for cells but also as a source of biological cues to promote tissue regeneration is currently a hot topic of in bone Tissue Engineering (TE) research. The inclusion of growth factor (GF) controlled release functionalities in the scaffolds is a possible strategy to achieve such goal. Platelet Lysate (PL) is an autologous source of GFs, providing several bioactive agents known to act on bone regeneration. In this study, chitosan-chondroitin sulfate nanoparticles loaded with PL were included in a poly(d,l-lactic acid) foam produced by supercritical fluid foaming. The tridimensional (3D) structures were then seeded with human adipose-derived stem cells (hASCs) and cultured in vitro under osteogenic stimulus. The osteogenic differentiation of the seeded hASCs was observed earlier for the PL-loaded constructs, as shown by the earlier alkaline phosphatase peak and calcium detection and stronger Runx2 expression at day 7 of culture, in comparison with the control scaffolds. Osteocalcin gene expression was upregulated in presence of PL during all culture period, which indicates an enhanced osteogenic induction. These results suggest the synergistic effect of PL and hASCs in combinatory TE strategies and support the potential of PL to increase the multifunctionality of the 3D hybrid construct for bone TE applications. {\textcopyright} 2012 Elsevier B.V. All rights reserved.

}, keywords = {Adipose derived stem cells, Bone tissue engineering, Controlled release, Platelet lysate, Scaffold, Supercritical fluids}, issn = {01683659}, doi = {10.1016/j.jconrel.2012.06.001}, author = {Santo, V.E. and Duarte, A.R.C. and Popa, E.G. and Gomes, M.E. and Mano, J.F. and Reis, R.L.} } @article {Duarte2012a, title = {{Ionic liquids as foaming agents of semi-crystalline natural-based polymers}}, journal = {Green Chemistry}, volume = {14}, number = {7}, year = {2012}, note = {n/a}, abstract = {

In this work, the ability to foam semi-crystalline natural-based polymers by supercritical fluid technology is evaluated. The application of this technique to natural polymers has been limited due to the fact that they are normally semi-crystalline polymers, which do not plasticize in the presence of carbon dioxide. This can be overcome by the use of plasticizers, such as glycerol, which is a commonly used plasticizer, or ionic liquids, which have recently been proposed as plasticizing agents for different polymers. Following the green chemistry principles, the main aim is, hereafter, the design and development of new 3D architectures of natural-based polymers, combining ionic liquids (IL) and supercritical fluid (SCF) technology. A polymeric blend of starch, one of the most abundantly occurring natural polymers, and poly-$ε$-caprolactone, a synthetic polymer, which is a biodegradable aliphatic polyester commonly used in an array of biomedical applications (SPCL), was processed by supercritical fluid foaming, at different operating conditions, namely pressure (10.0 up to 20.0 MPa), temperature (35 up to 60 {\textdegree}C) and soaking time (30 min up to 3 h). The ionic liquid tested in this work was 1-butyl-3-methylimidazolium acetate ([bmim]Ac). The interactions between SPCL and [bmim] Ac or glycerol were analysed by Fourier transform infrared spectroscopy, differential scanning calorimetry and by mechanical tests, using both tensile and compressive modes. Morphological analysis, porosity, interconnectivity and pore size distribution of the matrixes were evaluated and the morphology was analyzed by scanning electron microscopy and by micro-computed tomography. To our knowledge the use of ionic liquids as foaming agents is reported here for the first time. The results obtained suggest that this approach can further promote the development of composite polymer-IL materials, particularly for catalysis, chromatography, extraction and separation purposes. {\textcopyright} The Royal Society of Chemistry 2012.

}, issn = {14639262}, doi = {10.1039/c2gc16652f}, author = {Duarte, A.R.C. and Silva, S.S. and Mano, J.F. and Reis, R.L.} } @article {Alves2012, title = {{PDLLA enriched with ulvan particles as a novel 3D porous scaffold targeted for bone engineering}}, journal = {Journal of Supercritical Fluids}, volume = {65}, year = {2012}, note = {n/a}, pages = {32{\textendash}38}, publisher = {Elsevier B.V.}, abstract = {

A marine derived polysaccharide, ulvan, extracted from green algae, was combined with poly-d, l-lactic acid (PDLLA) in order to produce a novel scaffold for bone tissue engineering applications. Three dimensional (3D) scaffolds of PDLLA loaded with ulvan particles were originally prepared by subcritical fluid sintering with carbon dioxide at 40{\textdegree}C and 50 bar. Prepared matrixes were characterized in order to validate their suitability to be used as scaffolds for bone tissue regeneration. Characterization included micro-computed tomography, mechanical compression testing, water uptake and degradation testing, and cytotoxicity assays. In addition, ulvan particles loaded with dexamethasone, were also dispersed within the PDLLA matrix and the respective release profile from the samples was evaluated. Prepared PDLLA scaffolds enriched with ulvan particles demonstrated appropriate physicochemical and cytocompatible features to be used for the envisaged applications. On the other hand, the release of dexamethasone from ulvan particles embedded within the PDLLA matrix revealed that the designed systems can be potentially suitable for localized drug delivery. These results further contribute to the establishment of ulvan as a potential novel biomaterial. {\textcopyright} 2012 Elsevier B.V. All rights reserved.

}, keywords = {l-lactic acid, Poly-d, Scaffold, Subcritical sintering, tissue engineering, Ulvan}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2012.02.023}, url = {http://dx.doi.org/10.1016/j.supflu.2012.02.023}, author = {Alves, Anabela and Duarte, Ana Rita C and Jo{\~a}o F. Mano and Sousa, Rui A. and Reis, Rui L} } @article {Duarte2012, title = {{The role of organic solvent on the preparation of chitosan scaffolds by supercritical assisted phase inversion}}, journal = {Journal of Supercritical Fluids}, volume = {72}, year = {2012}, note = {n/a}, pages = {326{\textendash}332}, abstract = {

The aim of this study was to evaluate the possibility of preparing chitosan porous matrixes using supercritical fluid technology. Supercritical immersion precipitation technique was used to prepare scaffolds of a natural biocompatible polymer, chitosan for tissue engineering purposes. The physicochemical and biological properties of chitosan make it an excellent material for the preparation of drug delivery systems and for the development of new biomedical applications in many fields from skin to bone or cartilage. Supercritical assisted phase inversion experiments were carried out and the effect of different organic solvents on the morphology of the scaffolds was assessed. Chitosan scaffold morphology, porosity and pore size were evaluated by SEM and micro-CT. A thermodynamic analysis of the process was carried out and insights on the solubility parameter and Flory-Huggins interaction parameters are given. The preparation of a highly porous and interconnected structure of a natural material, chitosan, using a clean and environmentally friendly technology constitutes a new processing technology for the preparation of scaffolds for tissue engineering using these materials. {\textcopyright} 2011 Elsevier B.V.

}, keywords = {chitosan, Flory-Huggins interaction parameter, Scaffolds, Solubility parameter, Supercritical fluids, tissue engineering}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2010.12.004}, author = {Duarte, Ana Rita C and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Tutak2012, title = {{Tissue Engineering and Regenerative Medicine}}, journal = {Journal of Tissue Engineering and Regenerative Medicine}, volume = {6}, number = {i}, year = {2012}, note = {n/a}, pages = {1{\textendash}429}, abstract = {n/a}, isbn = {1932-7005}, issn = {19326254}, doi = {10.1002/term.1586}, url = {http://doi.wiley.com/10.1002/term.1586}, author = {Tutak, W and Farooque, T. and Simon, G C} } @article {Turner2012, title = {{Tissue Engineering and Regenerative Medicine}}, journal = {Journal of Tissue Engineering and Regenerative Medicine}, volume = {6}, year = {2012}, note = {n/a}, pages = {1{\textendash}429}, abstract = {n/a}, isbn = {1932-7005}, issn = {19326254}, doi = {10.1002/term.1586}, url = {http://doi.wiley.com/10.1002/term.1586}, author = {Turner, N J and Sicari, B M and Keane, T J and Londono, R and Crapo, P M and Tottey, S and Matsushima, R and Shimatsu, Y and Nam, K and Kimura, T and Fujisato, T} } @article {Silva2011, title = {{Green processing of porous chitin structures for biomedical applications combining ionic liquids and supercritical fluid technology}}, journal = {Acta Biomaterialia}, volume = {7}, number = {3}, year = {2011}, note = {n/a}, pages = {1166{\textendash}1172}, abstract = {

The application of green chemistry principles in the processing of materials for advanced technologies is a steadily increasing field of research. In this work porous chitin-based materials were developed by combining the processing of chitin using ionic liquids (ILs) as a green solvent together with the use of supercritical fluid technology (SCF) as clean technology. Chitin was dissolved in 1-butyl-3-imidazolium acetate, followed by regeneration of the polymer in ethanol in specific moulds. The IL was removed using Soxhlet extraction and successive steps of extraction with SCF using carbon dioxide/ethanol ratios of 50/50 and 70/30. The developed porous chitin-based structures (ChIL) can be classified as mesoporous materials, with very low density and high porosity. The cytotoxicity of ChIL extracts was investigated using L929 fibroblast-like cells, and the results demonstrated that the produced materials have extremely low cytotoxicity levels. Therefore, the findings suggest that the porous chitin structures may be potential candidates for a number of biomedical applications, including tissue engineering. {\textcopyright} 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

}, keywords = {biomaterials, Biomedical applications, Chitin, ionic liquids, Supercritical drying}, isbn = {1878-7568 (Electronic)$\backslash$r1742-7061 (Linking)}, issn = {17427061}, doi = {10.1016/j.actbio.2010.09.041}, author = {Silva, Simone S and Duarte, Ana Rita C and Carvalho, Ana Paula and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Trueba2011, title = {{Phase equilibrium measurements of structure II clathrate hydrates of hydrogen with various promoters}}, journal = {Fluid Phase Equilibria}, volume = {307}, number = {1}, year = {2011}, note = {n/a}, pages = {6{\textendash}10}, abstract = {

Phase equilibrium measurements of single and mixed organic clathrate hydrates with hydrogen were determined within a pressure range of 2.0-14.0. MPa. The organic compounds studied were furan, 2,5-dihydrofuran, tetrahydropyran, 1,3-dioxolane and cyclopentane. These organic compounds are known to form structure II clathrate hydrates with water. It was found that the addition of hydrogen to form a mixed clathrate hydrate increases the stability compared to the single organic clathrate hydrates. Moreover, the mixed clathrate hydrate also has a much higher stability compared to a pure hydrogen structure II clathrate hydrate. Therefore, the organic compounds act as promoter materials. The stabilities of the single and mixed organic clathrate hydrates with hydrogen showed the following trend in increasing order: 1,3-dioxolane {\textless} 2,5-dihydrofuran {\textless} tetrahydropyran {\textless} furan {\textless} cyclopentane, indicating that both size and geometry of the organic compound determine the stability of the clathrate hydrates. {\textcopyright} 2011 Elsevier B.V.

}, keywords = {1, 2, 3-Dioxolane, 5-Dihydrofuran, Clathrate hydrate, Cyclopentane, Furan, Hydrogen, Phase equilibrium, Structure II, Tetrahydropyran}, issn = {03783812}, doi = {10.1016/j.fluid.2011.04.025}, author = {Trueba, Alondra Torres and Rovetto, Laura J. and Florusse, Louw J. and Kroon, Maaike C. and Peters, Cor J.} } @article {Duarte2011, title = {{Thermosensitive polymeric matrices for three-dimensional cell culture strategies}}, journal = {Acta Biomaterialia}, volume = {7}, number = {2}, year = {2011}, note = {n/a}, abstract = {

A completely new strategy for cell culture focusing on the design of three-dimensional (3D) smart surfaces by supercritical fluid technology has been developed. This approach might overcome the limitations on cell expansion and proliferation of currently existing techniques. An alternative technology, based on supercritical carbon dioxide, was used to polymerize poly(N- isopropylacrylamide) (PNIPAAm) and to foam poly(d,l-lactic acid) (P D,L LA), creating a thermosensitive 3D structure which has proven to have potential as a substrate for cell growth and expansion. We demonstrated that the thermosensitive matrices promoted cell detachment, thus P D,L LA scaffolds have the potential to be used as substrates for cell growth and expansion avoiding enzymatic and mechanical methods of cell harvesting. The harvested cells were replated to evaluate their viability, which was not compromised. A major advantage of this technology is the fact that the prepared materials can be recovered and reused. Therefore, the same substrate can be recycled and reused for different batches. An indirect impact of the technology developed is related to the field of biotechnology, as this novel technology for cell expansion can be applied to any adherent cell cultures. {\textcopyright} 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

}, keywords = {Cell expansion, Poly-lactic acid, Supercritical fluids, Thermoresponsive matrices, tissue engineering}, issn = {17427061}, doi = {10.1016/j.actbio.2010.09.032}, author = {Duarte, A.R.C. and Mano, J.F. and Reis, R.L.} } @article {Costa2010, title = {{Development of therapeutic contact lenses using a supercritical solvent impregnation method}}, journal = {Journal of Supercritical Fluids}, volume = {52}, number = {3}, year = {2010}, note = {n/a}, pages = {306{\textendash}316}, abstract = {

We present some selected results indicating the feasibility of preparing therapeutic finished ophthalmic articles, namely commercially available soft contact lenses, using a supercritical solvent impregnation (SSI) technique. Several commercial soft contact lenses were tested and, among these, four lenses were selected for more complete studies: Nelfilcon A (FocusDailies{\textregistered}, CIBA Vision), Omafilcon A (Proclear{\textregistered} Compatibles, CooperVision), Methafilcon A (Frequency{\textregistered} 55, CooperVision) and Hilafilcon B (SofLens{\textregistered} 59 Comfort, Bausch {\&} Lomb). Supercritical carbon dioxide (scCO2) was the chosen supercritical fluid and two ophthalmic drugs were tested: flurbiprofen (a NSAID, hydrophobic) and timolol maleate (an anti-glaucoma drug, hydrophilic). The effects of operational pressure, of impregnation duration and of the addition of a cosolvent (ethanol) were studied on the overall drug loading yields. Depending on the experiment, we employed pressures from 9 up to 16 MPa and impregnation times from 30 up to 180 min. Temperature was kept constant and equal to 313 K. The employed depressurization rates were kept low and between 0.1 and 0.2 MPa/min. Results are discussed in terms of the employed operational conditions and taking in consideration all the possible interactions between supercritical fluids, drugs, cosolvents and the polymers which compose the employed hydrogel contact lenses. In vitro drug release experiments were carried out in order to evaluate the resulting drug release profiles. Obtained results were also compared with drug-loaded contact lenses obtained by conventional drug "soaking" in aqueous solutions. Results also proved that SSI can be considered as a viable, efficient and safe alternative for the impregnation of drugs, including those of hydrophobic character or presenting low aqueous solubility, into commercial soft contact lenses. SSI proved to be a "tunable" process since the variation of the employed operational conditions indicated that it is possible to control the amount of impregnated drug. In the end, the ophthalmic articles were recovered undamaged and without the presence of harmful solvent residues. This method also permits to process already prepared commercial contact lenses, without interfering with their manufacture methods and, after processing, store them for future use. {\textcopyright} 2010 Elsevier B.V. All rights reserved.

}, keywords = {Drug delivery systems, Supercritical solvent impregnation, Therapeutic contact lenses}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2010.02.001}, author = {Costa, Viviana P. and Braga, Mara E.M. and Guerra, Joana P. and Duarte, Ana R.C. and Duarte, Catarina M.M. and Leite, Eug{\'e}nio O.B. and Gil, Maria H. and de Sousa, Herm{\'\i}nio C.} } @article {Duarte2010a, title = {{Enzymatic degradation of 3D scaffolds of starch-poly-(?-caprolactone) prepared by supercritical fluid technology}}, journal = {Polymer Degradation and Stability}, volume = {95}, number = {10}, year = {2010}, note = {n/a}, pages = {2110{\textendash}2117}, abstract = {

Starch-based polymers have been proposed for different tissue engineering applications due to their inherent properties. In this work, a polymeric blend of starch-poly-(?-caprolactone) (SPCL) was processed using supercritical fluid technology, namely, by supercritical assisted phase inversion. As SPCL is a biodegradable polymer, the matrices produced are susceptible of undergoing enzymatic degradation upon implantation in the human body. In vitro assessment of the enzymatic degradation of SPCL was carried out in different buffer solutions containing a-amylase and/or lipase. The effect of the presence ofthese enzymes was studied by monitoring different parameters in order to characterise both bulk and the surface of the scaffolds. As regards to bulk analysis, weight loss of the samples incubated for 1, 3, 7, 14 and 21 days was determined, further differential scanning calorimetry was carried out. The morphology of the scaffolds after these periods was analysed by micro-computed tomography (?-CT) and surface chemistry was characterised by infra-red spectroscopy and contact angle measurements. Results suggest that SPLC scaffolds undergo bulk degradation, which is typically characterised by hydrolysis of chemical bonds in the polymer chain at the centre of the matrix, resulting in a highly porous material. ? 2010 Elsevier Ltd. All rights reserved.

}, keywords = {Enzymatic degradation, natural polymers, Polycaprolactone, starch, Supercritical fluids, tissue engineering}, isbn = {0141-3910}, issn = {01413910}, doi = {10.1016/j.polymdegradstab.2010.06.020}, author = {Duarte, Ana Rita C and Mano, Jo?o F. and Reis, Rui L} } @article {Santo2010, title = {{Hybrid 3D structure of poly(d,l-lactic acid) loaded with chitosan/chondroitin sulfate nanoparticles to be used as carriers for biomacromolecules in tissue engineering}}, journal = {Journal of Supercritical Fluids}, volume = {54}, number = {3}, year = {2010}, note = {n/a}, abstract = {

In the tissue engineering (TE) field, the concept of producing multifunctional scaffolds, capable not only of acting as templates for cell transplantation but also of delivering bioactive agents in a controlled manner, is an emerging strategy aimed to enhance tissue regeneration. In this work, a complex hybrid release system consisting in a three-dimensional (3D) structure based on poly(d,l-lactic acid) (PDLLA) impregnated with chitosan/chondroitin sulfate nanoparticles (NPs) was developed. The scaffolds were prepared by supercritical fluid foaming at 200 bar and 35 {\textdegree}C, and were then characterized by scanning electron microscopy (SEM) and micro-CT. SEM also allowed to assess the distribution of the NPs within the structure, showing that the particles could be found in different areas of the scaffold, indicating a homogeneous distribution within the 3D structure. Water uptake and weight loss measurements were also carried out and the results obtained demonstrated that weight loss was not significantly enhanced although the entrapment of the NPs in the 3D structure clearly enhances the swelling of the structure. Moreover, the hybrid porous biomaterial displayed adequate mechanical properties for cell adhesion and support. The possibility of using this scaffold as a multifunctional material was further evaluated by the incorporation of a model protein, bovine serum albumin (BSA), either directly into the PDLLA foam or in the NPs that were eventually included in the scaffold. The obtained results show that it is possible to achieve different release kinetics, suggesting that this system is a promising candidate for dual protein delivery system for TE applications. {\textcopyright} 2010 Elsevier B.V.

}, keywords = {chitosan, Chondroitin sulfate, Controlled release, l-lactic acid), Poly(d, Scaffolds, Supercritical fluid foaming, tissue engineering}, issn = {08968446}, doi = {10.1016/j.supflu.2010.05.021}, author = {Santo, V.E. and Duarte, A.R.C. and Gomes, M.E. and Mano, J.F. and Reis, R.L.} } @article {Sabil2010, title = {{Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution}}, journal = {International Journal of Greenhouse Gas Control}, volume = {4}, number = {5}, year = {2010}, note = {n/a}, pages = {798{\textendash}805}, publisher = {Elsevier Ltd}, abstract = {

A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide-tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time decreases with the increase of the initial carbon dioxide pressure up to 2.96. MPa. Beyond this pressure, the induction time is becoming relatively constant with the increase of initial carbon dioxide pressure indicating that the liquid phase is completely supersaturated with carbon dioxide. Experimental results show that the inclusion of tetrahydrofuran reduces the induction time required for hydrate formation. These observations indicate hydrate nucleation process and onset growth are more readily to occur in the presence of tetrahydrofuran. In contrast, the presence of sodium chloride prolongs the induction time due to clustering of water molecules with the ions and the salting-out effects. It is also shown that the degree of subcooling required for hydrate formation is affected by the presence of tetrahydrofuran and sodium chloride in the hydrate forming system. The presence of tetrahydrofuran in the hydrate system significantly reduces the amount of carbon dioxide uptake. The apparent rate constant, k, for those systems are reported. {\textcopyright} 2010.

}, keywords = {Carbon dioxide hydrate, Hydrate massive growth, Induction period, Kinetic of hydrate formation, Tetrahydrofuran}, isbn = {1750-5836}, issn = {17505836}, doi = {10.1016/j.ijggc.2010.05.010}, url = {http://dx.doi.org/10.1016/j.ijggc.2010.05.010}, author = {Sabil, Khalik M. and Duarte, Ana Rita C and Zevenbergen, John and Ahmad, Murni M. and Yusup, Suzana and Omar, Abdul A. and Peters, Cor J.} } @article {Duarte2010, title = {{Novel 3D scaffolds of chitosan-PLLA blends for tissue engineering applications: Preparation and characterization}}, journal = {Journal of Supercritical Fluids}, volume = {54}, number = {3}, year = {2010}, note = {n/a}, pages = {282{\textendash}289}, abstract = {

This work addresses the preparation of 3D porous scaffolds of blends of chitosan and poly(l-lactic acid), CHT and PLLA, using supercritical fluid technology. Supercritical assisted phase-inversion was used to prepare scaffolds for tissue engineering purposes. The physicochemical and biological properties of chitosan make it an excellent material for the preparation of drug delivery systems and for the development of new biomedical applications in many fields from skin to bone or cartilage regeneration. On the other hand, PLLA is a synthetic biodegradable polymer widely used for biomedical applications. Supercritical assisted phase-inversion experiments were carried out in samples with different polymer ratios and different polymer solution concentrations. The effect of CHT:PLLA ratio and polymer concentration and on the morphology and topography of the scaffolds was assessed by SEM and Micro-CT. Infra-red spectroscopic imaging analysis of the scaffolds allowed a better understanding on the distribution of the two polymers within the matrix. This work demonstrates that supercritical fluid technology constitutes a new processing technology, clean and environmentally friendly for the preparation of scaffolds for tissue engineering using these materials. {\textcopyright} 2010 Elsevier B.V.

}, keywords = {chitosan, Poly(l-lactic acid), Scaffolds, Supercritical fluids, tissue engineering}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2010.05.017}, author = {Duarte, Ana Rita C and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Martins2010, title = {{Osteogenic induction of hBMSCs by electrospun scaffolds with dexamethasone release functionality}}, journal = {Biomaterials}, volume = {31}, number = {22}, year = {2010}, note = {n/a}, abstract = {

Electrospun structures were proposed as scaffolds owing to their morphological and structural similarities with the extracellular matrix found in many native tissues. These fibrous structures were also proposed as drug release systems by exploiting the direct dependence of the release rate of a drug on the surface area. An osteogenic differentiation factor, dexamethasone (DEX), was incorporated into electrospun polycaprolactone (PCL) nanofibers at different concentrations (5, 10, 15 and 20 wt.{\%} polymer), in a single-step process. The DEX incorporated into the polymeric carrier is in amorphous state, as det ermined by DSC, and does not influence the typical nanofibers morphology. In vitro drug release studies demonstrated that the dexamethasone release was sustained over a period of 15 days. The bioactivity of the released dexamethasone was assessed by cultivating human bone marrow mesenchymal stem cells (hBMSCs) on 15 wt.{\%} DEX-loaded PCL NFMs, under dexamethasone-absent osteogenic differentiation medium formulation. An increased concentration of alkaline phosphatase and deposition of a mineralized matrix was observed. Phenotypic and genotypic expression of osteoblastic-specific markers corroborates the osteogenic activity of the loaded growth/differentiation factor. Overall data suggests that the electrospun biodegradable nanofibers can be used as carriers for the sustained release of growth/differentiation factors relevant for bone tissue engineering strategies. {\textcopyright} 2010 Elsevier Ltd.

}, keywords = {Bone tissue engineering, Drug release, Mesenchymal stem cells, Molecular biology, Polycaprolactone}, issn = {01429612}, doi = {10.1016/j.biomaterials.2010.04.010}, author = {A. Martins and Duarte, A.R.C. and Faria, S. and Marques, A.P. and Reis, R.L. and Neves, N.M.} } @book {Duarte2010c, title = {{Preparation of chitosan scaffolds for tissue engineering using supercritical fluid technology}}, series = {Materials Science Forum}, volume = {636-637}, year = {2010}, note = {n/a}, abstract = {

The aim of this study was to evaluate the possibility of preparing chitosan porous matrixes using supercritical fluid technology. Supercritical immersion precipitation technique was used to prepare scaffolds of a natural biocompatible polymer, chitosan, for tissue engineering purposes. The physicochemical and biological properties of chitosan make it an excellent material for the preparation of drug delivery systems and for the development of new biomedical applications in many fields from skin to bone or cartilage. Immersion precipitation experiments were carried out at different operational conditions in order to optimize the processing method. The effect of different organic solvents on the morphology of the scaffolds was assessed. Additionally, different parameters that influence the process were tested and the effect of the processing variables such as polymer concentration, temperature and pressure in the chitosan scaffold morphology, porosity and interconnectivity was evaluated by micro computed tomography. The preparation of a highly porous and interconnected structure of a natural material, chitosan, using a clean and environmentally friendly technology constitutes a new processing technology for the preparation of scaffolds for tissue engineering using these materials. {\textcopyright} (2010) Trans Tech Publications.

}, keywords = {Biopolymers, chitosan, Phase inversion, Scaffolds, Supercritical fluids, tissue engineering}, isbn = {0878492887}, issn = {02555476}, doi = {10.4028/www.scientific.net/MSF.636-637.22}, author = {Duarte, A.R.C. and Mano, J.F. and Reis, R.L.} } @article {Duarte2010b, title = {{Supercritical phase inversion of starch-poly($ε$-caprolactone) for tissue engineering applications}}, journal = {Journal of Materials Science: Materials in Medicine}, volume = {21}, number = {2}, year = {2010}, note = {n/a}, pages = {533{\textendash}540}, abstract = {

In this work, a starch-based polymer, namely a blend of starch-poly(epsilon-caprolactone) was processed by supercritical assisted phase inversion process. This processing technique has been proposed for the development of 3D structures with potential applications in tissue engineering applications, as scaffolds. The use of carbon dioxide as non-solvent in the phase inversion process leads to the formation of a porous and interconnected structure, dry and free of any residual solvent. Different processing conditions such as pressure (from 80 up to 150 bar) and temperature (45 and 55 degrees C) were studied and the effect on the morphological features of the scaffolds was evaluated by scanning electron microscopy and micro-computed tomography. The mechanical properties of the SPCL scaffolds prepared were also studied. Additionally, in this work, the in vitro biological performance of the scaffolds was studied. Cell adhesion and morphology, viability and proliferation was assessed and the results suggest that the materials prepared are allow cell attachment and promote cell proliferation having thus potential to be used in some for biomedical applications.

}, isbn = {1085600939}, issn = {09574530}, doi = {10.1007/s10856-009-3909-8}, author = {Duarte, Ana Rita C and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Duarte2009b, title = {{Dexamethasone-loaded scaffolds prepared by supercritical-assisted phase inversion}}, journal = {Acta Biomaterialia}, volume = {5}, number = {6}, year = {2009}, note = {n/a}, pages = {2054{\textendash}2062}, abstract = {

The aim of this study was to evaluate the possibility of preparing dexamethasone-loaded starch-based porous matrices in a one-step process. Supercritical phase inversion technique was used to prepare composite scaffolds of dexamethasone and a polymeric blend of starch and poly(l-lactic acid) (SPLA) for tissue engineering purposes. Dexamethasone is used in osteogenic media to direct the differentiation of stem cells towards the osteogenic lineage. Samples with different drug concentrations (5-15 wt.{\%} polymer) were prepared at 200 bar and 55 {\textdegree}C. The presence of dexamethasone did not affect the porosity or interconnectivity of the polymeric matrices. Water uptake and degradation studies were also performed on SPLA scaffolds. We conclude that SPLA matrices prepared by supercritical phase inversion have a swelling degree of nearly 90{\%} and the material presents a weight loss of \~{}25{\%} after 21 days in solution. Furthermore, in vitro drug release studies were carried out and the results show that a sustained release of dexamethasone was achieved over 21 days. The fitting of the power law to the experimental data demonstrated that drug release is governed by an anomalous transport, i.e., both the drug diffusion and the swelling of the matrix influence the release of dexamethasone out of the scaffold. The kinetic constant was also determined. This study reports the feasibility of using supercritical fluid technology to process in one step a porous matrix loaded with a pharmaceutical agent for tissue engineering purposes. {\textcopyright} 2009 Acta Materialia Inc.

}, keywords = {Drug delivery, Phase inversion, PLLA, Supercritical fluids, tissue engineering}, isbn = {1742-7061}, issn = {17427061}, doi = {10.1016/j.actbio.2009.01.047}, author = {Duarte, Ana Rita C and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Duarte2009a, title = {{Perspectives on: Supercritical fluid technology for 3d tissue engineering scaffold applications}}, journal = {Journal of Bioactive and Compatible Polymers}, volume = {24}, number = {4}, year = {2009}, note = {n/a}, pages = {385{\textendash}400}, abstract = {

Supercritical fluid technology has proven to be useful for many pharmaceutical applications and is now emerging as an alternative to conventional processes for the preparation of 3D structures and injectable particles suitable to be used in regenerative medicine. A current overview of the basic principles underlying supercritical fluid technology, the state of the art and future potential of this technology are presented.

}, keywords = {Drug delivery, Foaming, Impregnation, Phase inversion, Polymer, Scaffolds, Sterilization., Supercritical fluids, tissue engineering}, issn = {08839115}, doi = {10.1177/0883911509105796}, author = {Duarte, Ana Rita C and Mano, Joo F. and Reis, Rui L} } @article {Duarte2009d, title = {{Preparation of chitosan scaffolds loaded with dexamethasone for tissue engineering applications using supercritical fluid technology}}, journal = {European Polymer Journal}, volume = {45}, number = {1}, year = {2009}, note = {n/a}, pages = {141{\textendash}148}, abstract = {

Supercritical fluid impregnation was tested to prepare a new scaffold loaded with a bioactive compound. Dexamethasone is used in osteogenic media to direct the differentiation of stem cells towards the osteogenic lineage. Dexamethasone was impregnated in chitosan scaffolds at different operating conditions, in order to optimize the impregnation process. Pressure and temperature affect the carbon dioxide density and influence the swelling of the polymer and the drug solubility in the fluid phase, therefore these are two important parameters that were studied in this work. Chitosan sponges prepared by freeze drying were impregnated with the active compound at pressures from 8.0 up to 14.0 MPa and temperatures from 35 up to 55 {\textdegree}C. The effect of the impregnation contact time (3 h and 6 h) was also evaluated. From the experiments performed we can conclude that the yield of impregnation is lower when increasing pressure and temperature. The contact time will mainly influence the amount of drug impregnated in the scaffold and for higher contact times the impregnation yield is also higher. Scanning electron microscopy shows particles of dexamethasone in the bulk of the scaffold, which confirms the feasibility of the supercritical fluid impregnation technology for the preparation of delivery devices. The loading capacity of the scaffolds was determined by spectroscopic analysis and the highest loading was achieved for the experiments performed at 8.0 MPa and 35 {\textdegree}C. Furthermore, in vitro drug release studies were carried out and the results show that dexamethasone was sustainably released. Supercritical fluid impregnation proved to be feasible for the preparation of a drug delivery system for bone tissue engineering purposes. {\textcopyright} 2008 Elsevier Ltd. All rights reserved.

}, keywords = {chitosan, Dexamethasone, Drug delivery, Impregnation, Scaffolds, Supercritical fluids}, isbn = {0014-3057}, issn = {00143057}, doi = {10.1016/j.eurpolymj.2008.10.004}, author = {Duarte, Ana Rita C and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Duarte2009c, title = {{Preparation of starch-based scaffolds for tissue engineering by supercritical immersion precipitation}}, journal = {Journal of Supercritical Fluids}, volume = {49}, number = {2}, year = {2009}, note = {n/a}, pages = {279{\textendash}285}, abstract = {

The aim of this study was to evaluate the possibility of preparing starch-based porous matrixes using supercritical fluid technology. Supercritical immersion precipitation technique was used to prepare scaffolds of a polymeric blend of starch and poly(l-lactic acid) for tissue engineering purposes.Immersion precipitation experiments were carried out at different operational conditions and highly porous and interconnected scaffolds were obtained. Two organic solvents, dichloromethane and chloroform were tested, and from the results obtained chloroform was the more favourable for the process. The effect of polymer solution concentration (5 up to 20 wt{\%}), temperature (35 up to 55 {\textdegree}C) and pressure (100 up to 200 bar) in the SPLA (50:50 wt{\%}) membrane morphology, porosity and interconnectivity was evaluated. All the conditions tested were in the region of total miscibility between the organic solvent and carbon dioxide. Additionally, a blend with a different starch-poly(l-lactic acid) ratio (30:70 wt{\%}) was tested. Bicontinuous structures were formed indicating that the L-L demixing process that governs the phase inversion is the spinodal decomposition. {\textcopyright} 2008 Elsevier B.V. All rights reserved.

}, keywords = {Immersion precipitation, natural polymers, Phase inversion, PLLA, Scaffolds, Supercritical fluids, tissue engineering}, isbn = {08968446}, issn = {08968446}, doi = {10.1016/j.supflu.2008.12.008}, author = {Duarte, Ana Rita C and Jo{\~a}o F. Mano and Reis, Rui L} } @article {Duarte2009, title = {{Processing of novel bioactive polymeric matrixes for tissue engineering using supercritical fluid technology}}, journal = {Materials Science and Engineering C}, volume = {29}, number = {7}, year = {2009}, note = {n/a}, pages = {2110{\textendash}2115}, abstract = {

The aim of this study was to develop a new process for the production of bioactive 3D scaffolds using a clean and environmentally friendly technology. The possibility of preparing composite scaffolds of Bioglass?? and a polymeric blend of starch and poly(l-lactic acid) (SPLA50) was evaluated. Supercritical phase-inversion technique was used to prepare inorganic particles loaded starch-based porous composite matrixes in a one-step process for bone tissue engineering purposes. Due to their osteoconductive properties some glasses and ceramics are interesting materials to be used for bone tissue engineering purposes; however their poor mechanical properties create the need of a polymeric support where the inorganic fraction can be dispersed. Samples impregnated with different concentrations of Bioglass?? (10 and 15{\%} wt/wt polymer) were prepared at 200??bar and 55????C. The presence of Bioglass?? did not affect the porosity or interconnectivity of the polymeric matrixes. Dynamic mechanical analysis has proven that the modulus of the SPLA50 scaffolds increases when glass particles are impregnated within the matrix. In vitro bioactivity studies were carried out using simulated body fluid and the results show that a calcium-phosphate layer started to be formed after only 1??day of immersion. Chemical analysis of the apatite layer formed on the surface of the scaffold was performed by different techniques, namely EDS and FTIR spectroscopy and X-ray diffraction (XRD). The ion concentration in the simulated body fluid was also carried out by ICP analysis. Results suggest that a bone-like apatite layer was formed. This study reports the feasibility of using supercritical fluid technology to process, in one step, a porous matrix loaded with a bioactive material for tissue engineering purposes. ?? 2009 Elsevier B.V. All rights reserved.

}, keywords = {Bioglass??, natural polymers, Phase inversion, PLLA, Supercritical fluids, tissue engineering}, isbn = {0928-4931}, issn = {09284931}, doi = {10.1016/j.msec.2009.04.012}, author = {Duarte, Ana Rita C and Caridade, Sofia G. and Mano, Jo??o F. and Reis, Rui L} } @article {Duarte2009e, title = {{Supercritical fluids in biomedical and tissue engineering applications: a review}}, journal = {International Materials Reviews}, volume = {54}, number = {4}, year = {2009}, note = {n/a}, pages = {214{\textendash}222}, abstract = {

Over the past several years, the definition of a scaffold for tissue engineering has changed dramatically, from a material that acts only as an inert structural support for cell attachment to serving as a more complex and dynamic environment for tissue development. This paper is a review on the existing and on the new emerging techniques based on supercritical fluid technology for the preparation of scaffolds and particles for tissue engineering applications. Supercritical fluid technology has already proven to be feasible for many pharmaceutical applications and is now emerging as an alternative to conventional materials{\textquoteright} processing methods for the preparation of three-dimensional structures and injectable particles suitable to be used in regenerative medicine. The basic principles underlying each technique are here presented as well as the advantages and disadvantages of each process. The state of the art is reviewed and the major conclusions of the studies reported in the literature are discussed.

}, isbn = {0950-6608}, issn = {0950-6608}, doi = {10.1179/174328009X411181}, url = {http://www.tandfonline.com/doi/full/10.1179/174328009X411181}, author = {Duarte, A.R.C. and Mano, J.F. and Reis, R.L.} } @article {Coimbra2008, title = {{T O T S I U Rib N Tio T O T S I N}}, year = {2008}, note = {n/a}, pages = {102{\textendash}107}, abstract = {n/a}, keywords = {anti-inflammatory agents, Biocompatible polymers, Impregnation, Ophthalmic drug delivery, Supercritical fluids}, author = {Coimbra, Patr{\'\i}cia and Gil, MH and Sousa, Herminio C De and Duarte, Catarina M.M.} } @article {Duarte2008, title = {{Water cavities of sH clathrate hydrate stabilized by molecular hydrogen: Phase equilibrium measurements}}, journal = {Journal of Physical Chemistry B}, volume = {112}, number = {7}, year = {2008}, note = {n/a}, abstract = {

In this experimental phase equilibrium study, we show for the first time that it is possible to stabilize structure sH of hydrogen clathrate hydrate with the help of some selected promoters. It was established that the formation pressures of these systems are significantly higher than that of structure sII of hydrogen clathrate hydrate when tetrahydrofuran (THF) is used as a promoter. Although no experimental evidence is available yet, it is estimated that the hydrogen storage capacity of structure sH can be as high as 1.4 wt {\%} of H 2 , which is about 40{\%} higher compared to the hydrogen storage capacity in structure sH. {\textcopyright} 2008 American Chemical Society.

}, issn = {15206106}, doi = {10.1021/jp7110605}, author = {Duarte, A.R.C. and Shariati, A. and Rovetto, L.J. and Peters, C. J.} } @article {Duarte2007a, title = {{Preparation of acetazolamide composite microparticles by supercritical anti-solvent techniques}}, journal = {International Journal of Pharmaceutics}, volume = {332}, number = {1-2}, year = {2007}, note = {n/a}, pages = {132{\textendash}139}, abstract = {

The possibility of preparation of ophthalmic drug delivery systems using compressed anti-solvent technology was evaluated. Eudragit RS 100 and RL 100 were used as drug carriers, acetazolamide was the model drug processed. Compressed anti-solvent experiments were carried out as a semi-continuous or a batch operation from a liquid solution of polymer(s) + solute dissolved in acetone. Both techniques allowed the recovery of composite particles, but the semi-continuous operation yielded smaller and less aggregated populations than the batch operation. The release behaviour of acetazolamide from the prepared microparticles was studied and most products exhibited a slower release than the single drug. Moreover, the release could be controlled to some extent by varying the ratio of the two Eudragit used in the formulation and by selecting one or the other anti-solvent technique. Simple diffusion models satisfactorily described the release profiles. Composites specifically produced by semi-continuous technique have a drug release rate controlled by a diffusion mechanism, whereas for composites produced by the batch operation, the polymer swelling also contributes to the overall transport mechanism. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, keywords = {Acetazolamide, Drug delivery, Eudragit, GAS, SAS, Supercritical fluids}, isbn = {0378-5173 (Print)$\backslash$r0378-5173 (Linking)}, issn = {03785173}, doi = {10.1016/j.ijpharm.2006.09.041}, author = {Duarte, Ana Rita C and Roy, Christelle and Vega-Gonz{\'a}lez, Arlette and Duarte, Catarina M.M. and Subra-Paternault, Pascale} } @article {Duarte2007b, title = {{Preparation of acetazolamide composite microparticles by supercritical anti-solvent techniques}}, journal = {International Journal of Pharmaceutics}, volume = {332}, number = {1-2}, year = {2007}, note = {n/a}, pages = {132{\textendash}139}, abstract = {

The possibility of preparation of ophthalmic drug delivery systems using compressed anti-solvent technology was evaluated. Eudragit RS 100 and RL 100 were used as drug carriers, acetazolamide was the model drug processed. Compressed anti-solvent experiments were carried out as a semi-continuous or a batch operation from a liquid solution of polymer(s) + solute dissolved in acetone. Both techniques allowed the recovery of composite particles, but the semi-continuous operation yielded smaller and less aggregated populations than the batch operation. The release behaviour of acetazolamide from the prepared microparticles was studied and most products exhibited a slower release than the single drug. Moreover, the release could be controlled to some extent by varying the ratio of the two Eudragit used in the formulation and by selecting one or the other anti-solvent technique. Simple diffusion models satisfactorily described the release profiles. Composites specifically produced by semi-continuous technique have a drug release rate controlled by a diffusion mechanism, whereas for composites produced by the batch operation, the polymer swelling also contributes to the overall transport mechanism. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, keywords = {Acetazolamide, Drug delivery, Eudragit, GAS, SAS, Supercritical fluids}, isbn = {0378-5173 (Print)$\backslash$r0378-5173 (Linking)}, issn = {03785173}, doi = {10.1016/j.ijpharm.2006.09.041}, author = {Duarte, Ana Rita C and Roy, Christelle and Vega-Gonz{\'a}lez, Arlette and Duarte, Catarina M.M. and Subra-Paternault, Pascale} } @article {Cravo2007, title = {{Solubility of carbon dioxide in a natural biodegradable polymer: Determination of diffusion coefficients}}, journal = {Journal of Supercritical Fluids}, volume = {40}, number = {2}, year = {2007}, note = {n/a}, abstract = {

Carbon dioxide solubility in a natural biodegradable polymer, namely poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and the diffusion coefficients are reported. Equilibrium solubility of dense carbon dioxide in PHBV was studied by a gravimetric method in a temperature range from 308 to 313 K and a pressure range from 10.0 to 15.0 MPa. The copolymer presented Fickian behavior and Fick{\textquoteright}s diffusion model was applied to determine the amount of carbon dioxide present in the samples after a predermined exposure time as well as the diffusion coefficients. Diffusion coefficients for the sorption under supercritical (sc) conditions and desorption at ambient conditions were determined and compared. To evaluate the influence of the HV content in the amount of maximum sorption degree of the polymer, different samples of PHBV copolymers were tested and the sorption curves are here presented. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, keywords = {Biodegradable natural polymers, Carbon dioxide, Diffusion coefficients, PHBV, sorption}, issn = {08968446}, doi = {10.1016/j.supflu.2006.07.004}, author = {Cravo, C. and Duarte, A.R.C. and Duarte, C.M.M.} } @article {Costa2007, title = {{Supercritical antisolvent precipitation of PHBV microparticles}}, journal = {International Journal of Pharmaceutics}, volume = {328}, number = {1 SPEC. ISS.}, year = {2007}, note = {n/a}, pages = {72{\textendash}77}, abstract = {

The micronization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from organic solutions using supercritical antisolvent (SAS) technique has been successfully achieved. SAS experiments were carried out at different operational conditions and microspheres with mean diameters ranging from 3 to 9 $μ$m were obtained. The effect of CO2 and liquid flow, temperature and pressure on particle size and particle size distribution was evaluated. The microspheres were precipitated from a dichloromethane (DCM) solution. The best process conditions for this mixture were, according to our study, 40 {\textdegree}C, 100 bar, 1 mL min-1 liquid flow and 10 L min-1 carbon dioxide flow. Experiments with polymers containing different HV percentages were carried out. The powders obtained became more spherical as the HV content decreased. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, keywords = {Drug delivery, Micronization, natural polymers, PHBV, SAS, Supercritical fluids}, isbn = {0032-5910}, issn = {03785173}, doi = {10.1016/j.ijpharm.2006.08.004}, author = {Costa, Mariana Sousa and Duarte, Ana Rita C and Cardoso, M. Margarida and Duarte, Catarina M.M.} } @article {Duarte2007, title = {{Supercritical fluid impregnation of a biocompatible polymer for ophthalmic drug delivery}}, journal = {Journal of Supercritical Fluids}, volume = {42}, number = {3 SPEC. ISS.}, year = {2007}, note = {n/a}, pages = {373{\textendash}377}, abstract = {

Supercritical fluid impregnation was tested to prepare a new ophthalmic drug delivery device. Poly(methylmethacrylate-co-ethylhexylacrylate-co-ethyleneglycoldimethacr ylate), P(MMA-EHA-EGDMA) has been proposed by Mariz [M. Mariz, Prepara{\c c}{\~a}o de uma lente intra-ocular dotada de um sistema de liberta{\c c}{\~a}o controlada de f{\'a}rmaco, Master Thesis, Universidade de Coimbra, 1999] as a promising matrix to be used for intraocular delivery of anti-inflammatory drugs used in eye surgery. This matrix was successfully impregnated with flurbiprofen, a non-steroidal anti-inflammatory agent. The success of the impregnation was evaluated by scanning electron microscopy (SEM) analysis and also by in vitro drug release studies. The effect of some operating parameters was evaluated, namely, pressure and contact time. The operating pressure will influence both the solubility of the drug in the supercritical fluid but also the sorption degree of the polymeric matrix in the presence of carbon dioxide. The solubility of the drug in carbon dioxide and the sorption degree are reported in previous studies. A comparison between the batch and the semi-continuous impregnation process is also presented. The supercritical fluid impregnation proved to be feasible for the preparation of a new ophthalmic drug delivery system. The drug release profiles suggest that the drug can be released up to three months, which is a major advantage for the prevention of the inflammatory response after ophthalmic surgery. {\textcopyright} 2007 Elsevier B.V. All rights reserved.

}, keywords = {Biocompatible polymers, Impregnation, Ophthalmic drug delivery, Supercritical fluids}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2007.01.007}, author = {Duarte, Ana Rita C and Simplicio, Ana Luisa and Vega-Gonz{\'a}lez, Arlette and Subra-Paternault, Pascale and Coimbra, Patr{\'\i}cia and Gil, MH and de Sousa, Herminio C. and Duarte, Catarina M.M.} } @article {Duarte2006c, title = {{Preparation of controlled release microspheres using supercritical fluid technology for delivery of anti-inflammatory drugs}}, journal = {International Journal of Pharmaceutics}, volume = {308}, number = {1-2}, year = {2006}, note = {n/a}, pages = {168{\textendash}174}, abstract = {

Ethylcellulose/methylcellulose blends were produced using different precipitation techniques and impregnated with naproxen, a non-steroidal anti-inflammatory drug (NSAID). Solvent-evaporation technique was used not only for the preparation of ethylcellulose/methylcellulose microspheres but also to encapsulate naproxen. Supercritical fluid (SCF) impregnation was also performed to prepare naproxen loaded microspheres. The microspheres, impregnated by the SCF technique, were prepared both by solvent-evaporation and by a supercritical antisolvent (SAS) process. In vitro release profiles at pH 7.4 and 1.2, of naproxen-loaded microspheres were evaluated and the results were modelled Fick{\textquoteright}s law of diffusion and Power law. Miscrospheres prepared by supercritical antisolvent have a higher loading capacity and present a slower release profile. The systems studied present a release mechanism controlled by drug diffusion which complies Fick{\textquoteright}s law of diffusion. {\textcopyright} 2005 Elsevier B.V. All rights reserved.

}, keywords = {Anti-inflammatory drugs, Controlled delivery systems, Ethylcellulose, SAS, Supercritical fluids}, isbn = {0378-5173 FIELD Electronic Internat.Standard Doc. Number:}, issn = {03785173}, doi = {10.1016/j.ijpharm.2005.11.012}, author = {Duarte, Ana Rita C and Costa, Mariana Sousa and Simpl{\'\i}cio, Ana Lu{\'\i}sa and Cardoso, Maria Margarida and Duarte, Catarina M.M.} } @article {Duarte2006b, title = {{Preparation of ethyl cellulose/methyl cellulose blends by supercritical antisolvent precipitation}}, journal = {International Journal of Pharmaceutics}, volume = {311}, number = {1-2}, year = {2006}, note = {n/a}, pages = {50{\textendash}54}, abstract = {

The supercritical antisolvent (SAS) technique was used to prepare ethyl cellulose/methyl cellulose blends, two biocompatible polymers commonly used as drug carriers in controlled delivery systems. Ethyl cellulose is widely used as a drug carrier. The drug release of the delivery devices can be controlled to some extent by addition of a water-soluble or water swellable polymer, such as methyl cellulose. This leads to the solubility enhancement of poorly water-soluble molecules. SAS experiments were carried out at different operational conditions and microspheres with mean diameters ranging from 5 to 30 $μ$m were obtained. The effect of CO2 and liquid flow, temperature and pressure on particle size and particle size distribution was evaluated. The microspheres were precipitated from a mixture of dichloromethane (DCM) and dimethylsulfoxide (DMSO) (4:1 ratio). The best process conditions for this mixture were according to our study 40{\textdegree}C and 80 bar. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, keywords = {Biocompatible polymers, Micronization, Release systems, Supercritical fluid antisolvent (SAS)}, issn = {03785173}, doi = {10.1016/j.ijpharm.2005.12.010}, author = {Duarte, Ana Rita C and Gordillo, M. D. and Cardoso, M. Margarida and Simpl{\'\i}cio, Ana Lu{\'\i}sa and Duarte, Catarina M.M.} } @article {Duarte2006a, title = {{Sorption and diffusion of dense carbon dioxide in a biocompatible polymer}}, journal = {Journal of Supercritical Fluids}, volume = {38}, number = {3}, year = {2006}, note = {n/a}, pages = {392{\textendash}398}, abstract = {

Mass sorption and diffusion coefficients in one acrylate biocompatible copolymer contacted with supercritical (sc) carbon dioxide are reported. Equilibrium solubility of dense carbon dioxide in poly(methylmethacrylate-co-ethylhexylacrylate-co-ethyleneglycoldimethacr ylate) (P(MMA-EHA-EGDMA)) was studied by a gravimetric method in a temperature range from 308 to 323 K and a pressure range from 10.0 to 20.0 MPa. The cross-linked copolymer presented Fickian behavior and Fick{\textquoteright}s diffusion model was applied to determine the amount of carbon dioxide present and the diffusion coefficients. Diffusion coefficients for the sorption under supercritical conditions and desorption at ambient conditions were determined and compared. Samples of P(MMA-EHA-EGDMA) with different thickness were used for comparison of the maximum sorption degree. Polymerization conditions were also varied in order to evaluate the influence of the molecular weight of the copolymer in the CO2 sorption process. To investigate the possibility of impregnating this acrylate copolymer with an anti-inflammatory drug, a preliminary experiment was performed. {\textcopyright} 2005 Elsevier B.V. All rights reserved.

}, keywords = {Biocompatible polymers, Diffusion, Fick{\textquoteright}s law, sorption, Supercritical fluids}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2005.12.002}, author = {Duarte, Ana Rita C and Martins, Carlos and Coimbra, Patr{\'\i}cia and Gil, Maria H.M. and de Sousa, Herm{\'\i}nio C. and Duarte, Catarina M.M.} } @article {Duarte2006, title = {{Supercritical fluid polymerisation and impregnation of molecularly imprinted polymers for drug delivery}}, journal = {Journal of Supercritical Fluids}, volume = {39}, number = {1}, year = {2006}, note = {n/a}, pages = {102{\textendash}106}, abstract = {

Herein the preparation of molecularly imprinted polymers (MIPs) using supercritical fluid technology is evaluated. Poly(diethylene glycol dimethacrylate), polyDEGDMA, was synthesised in supercritical carbon dioxide (scCO2) using a carboxylic acid end-capped perfluoropolyether oil as stabiliser. Polymerisations were carried out in the presence of different concentrations of two different template drug molecules, salicylic acid and acetylsalicylic acid. Results suggest that molecular imprinted polymers were successfully prepared by supercritical polymerisation and then impregnated with the template in order to prepare controlled release systems. {\textcopyright} 2006 Elsevier B.V. All rights reserved.

}, keywords = {Cross-linking, Diethylene glycol dimethacrylate, Impregnation, Molecular imprinting, polymerisation, supercritical carbon dioxide}, isbn = {0896-8446}, issn = {08968446}, doi = {10.1016/j.supflu.2006.01.013}, author = {Duarte, Ana Rita C and Casimiro, Teresa and Aguiar-Ricardo, Ana and Simpl{\'\i}cio, Ana Lu{\'\i}sa and Duarte, Catarina M.M.} } @article {Duarte2005a, title = {{A comparison between gravimetric and in situ spectroscopic methods to measure the sorption of CO{\textless}inf{\textgreater}2{\textless}/inf{\textgreater} in a biocompatible polymer}}, journal = {Journal of Supercritical Fluids}, volume = {36}, number = {2}, year = {2005}, note = {n/a}, abstract = {

In situ ATR-IR spectroscopy was used to simultaneously measure the sorption and swelling of carbon dioxide at high pressures in a biocompatible acrylate copolymer poly(methylmethacrylate-co-ethylhexylacrylate-co- ethyleneglycoldimethacrylate), P(MMA-EHA-EGDMA). The $ν$ 3 band of CO 2 dissolved in the polymer (at 2335 cm -1 ) was used to calculate the sorption data and the polymer swelling was determined by analyzing the changes in the absorbance of the $ν$(CO) band (at 1730 cm -1 ) of the polymer. Transmission spectroscopy in the near-IR region was also used to study the sorption of CO 2 in the polymer using combinational and overtone bands. The experiments were carried out in a pressure range of 2.0-12.0 MPa and in a temperature range of 27-40 {\textdegree}C. The data for CO 2 sorption in this polymer obtained by in situ spectroscopic methods have been compared to the data obtained by the gravimetric technique. {\textcopyright} 2005 Elsevier B.V. All rights reserved.

}, keywords = {ATR-FTIR, CO sorption 2, Near-IR spectroscopy, Polymer swelling}, issn = {08968446}, doi = {10.1016/j.supflu.2005.04.003}, author = {Duarte, A.R.C. and Anderson, L.E. and Duarte, C.M.M. and Kazarian, S.G.} } @article {Duarte2005, title = {{Solubility of acetazolamide in supercritical carbon dioxide in the presence of ethanol as a cosolvent}}, journal = {Journal of Chemical and Engineering Data}, volume = {50}, number = {1}, year = {2005}, note = {n/a}, pages = {216{\textendash}220}, abstract = {

Equilibrium solubility of acetazolamide, a carbonic-anhydrase inhibitor, in supercritical carbon dioxide in the presence of a cosolvent was measured by a static analytical method for three mole fractions of ethanol (5, 7.5, and 10) {\%} at 313.0 K from (13.0 to 21.0) MPa and at 323.0 K from (13.0 to 21.0) MPa for a mole fraction of 5{\%} ethanol The presence of a cosolvent (ethanol) was essential for the solubilization of the bioactive compound in supercritical carbon dioxide. The results obtained are useful for the design of supercritical processes with this drug. Experimental solubility data were correlated with two enhanced density-based models (Chrastil, I. Solubility of Solids in Supercritical Gases. J. Phys. Chem. 1982, 86, 3016-3021; Santiago, J. M.; Teja, A. S. The solubility of solids in supercritical fluids. Fluid Phase Equilib. 1999, 158-160, 501-510).

}, issn = {00219568}, doi = {10.1021/je049722m}, author = {Duarte, Ana Rita C and Santiago, Susana and {De Sousa}, Herm{\'\i}nio C. and Duarte, Catarina M.M.} } @article {Duarte2004, title = {{Solubility of flurbiprofen in supercritical carbon dioxide}}, journal = {Journal of Chemical and Engineering Data}, volume = {49}, number = {3}, year = {2004}, note = {n/a}, abstract = {

Equilibrium solubility of flurbiprofen, a nonsteroidal antiinflammatory agent, in supercritical carbon dioxide was measured by a static analytical method in the pressure range from (8.0 to 25.0) MPa, at temperatures of (303.0, 313.0, and 323.0) K. The cosolvent effect of ethanol in the solubility of the bioactive compound in supercritical carbon dioxide was investigated at 18 MPa and 313 K. The results obtained have a potential application in supercritical processes for this drug. Experimental solubility data were correlated with an empirical density-based Chrastil model.

}, issn = {00219568}, doi = {10.1021/je034099b}, author = {Duarte, A.R.C. and Coimbra, P. and {De Sousa}, H.C. and Duarte, C.M.M.} } @article {CruzDuarte2003, title = {{Measurement and modelling of bubble and dew points in the binary systems carbon dioxide + cyclobutanone and propane + cyclobutanone}}, journal = {Fluid Phase Equilibria}, volume = {214}, number = {2}, year = {2003}, note = {n/a}, pages = {121{\textendash}136}, abstract = {

The fluid phase behaviour for the binary systems carbon dioxide+cyclobutanone and propane+cyclobutanone has been determined experimentally, using Cailletet equipment. For both the systems bubble points have been determined for a number of isopleths covering the whole mole fraction range. Additionally, for the binary system carbon dioxide+cyclobutanone dew points and critical points could be observed for a number of overall-compositions rich in carbon dioxide. The temperature and pressure range were, respectively, from 278 to 369K and from 0.1 to 14.0MPa. Correlation of the experimental data of both systems has been performed using the Soave-Redlich-Kwong (SRK) equation of state. Satisfactory results have been achieved using only one binary interaction parameter. {\textcopyright} 2003 Elsevier B.V. All rights reserved.

}, keywords = {Carbon dioxide, Cyclobutanone, Modelling, Phase behaviour, Propane}, issn = {03783812}, doi = {10.1016/S0378-3812(03)00325-X}, author = {{Cruz Duarte}, A. R. and {Mooijer-Van Den Heuvel}, M. M. and Duarte, C.M.M. and Peters, C. J.} }