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Alves A, Duarte AR, Mano JF, Sousa RA, Reis RL. {PDLLA enriched with ulvan particles as a novel 3D porous scaffold targeted for bone engineering}. Journal of Supercritical Fluids. 2012;65:32-8. Abstractpdf

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°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. © 2012 Elsevier B.V. All rights reserved.

Aroso IM, Craveiro R, Rocha Â, Dionísio M, Barreiros S, Reis RL, Paiva A, Duarte AR. {Design of controlled release systems for THEDES - Therapeutic deep eutectic solvents, using supercritical fluid technology}. International Journal of Pharmaceutics. 2015;492. Abstract

© 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-Ï$μ$-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 °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.

Aroso IM, Silva JC, Mano F, Ferreira AS, Dionísio M, Sá-Nogueira I, Barreiros S, Reis RL, Paiva A, Duarte AR. {Dissolution enhancement of active pharmaceutical ingredients by therapeutic deep eutectic systems}. European Journal of Pharmaceutics and Biopharmaceutics. 2016;98:57-66. Abstractpdf

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.

Aroso IM, Paiva A, Reis RL, Duarte AR. {Natural deep eutectic solvents from choline chloride and betaine – Physicochemical properties}. Journal of Molecular Liquids. 2017;241. Abstract

© 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.

Aroso IM, Duarte AR, Pires RR, Mano JF, Reis RL. {Cork processing with supercritical carbon dioxide: Impregnation and sorption studies}. Journal of Supercritical Fluids. 2015;104:251-8. Abstractpdf

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.