Jimena S. Gonzalez

Development and characterization of Poly (vinyl alcohol) based hydrogels for potential use as an articular cartilage replacement

Hydroxyapatite (HA) reinforced Poly(vinyl alcohol) (PVA) hydrogel composites has been proposed as a promising biomaterial to replace diseased or damaged articular cartilage. Here, PVA/in-situ produced HA hydrogels with 0, 3 and 7.5 wt.% of HA content were obtained by freezing/thawing technique. Thermal, structural and mechanical characterizations were carried out. SEM micrographs revealed that HA was homogeneously distributed in PVA until 3 wt.% whereas partial agglomeration was observed for higher contents (7.5 wt.%). No significant changes were observed in the glass transition temperature (the average value was near to 78 °C ± 3 °C), the melting point and structural water content whereas the gel fraction slightly increased (from 0.72 to 0.78) with the increase the content of HA. The absorbed water decreased (from 85.7% to 80.5%) as a function of HA content The stress-strain curves were really different in hydrated and non-hydrated conditions, changing from non-linear, in presence of water, to linear behavior in a dried state, being in the first case consistent with the articular cartilage . The lowest friction coefficient was obtained for samples with 3 wt. % HA (0.067 ± 0.049), which is, together with a high resistance (721 ± 25 kPa), an important property for materials that will be used as articular replacement. The results indicate that this hydrogel could be used, after other studies, as articular cartilage replacement.

Modified bacterial cellulose scaffolds for localized doxorubicin release in human colorectal HT-29 cells.

Bacterial cellulose (BC) films modified by the in situ method with the addition of alginate (Alg) during the microbial cultivation of Gluconacetobacter hansenii under static conditions increased the loading of doxorubicin by at least three times. Biophysical analysis of BC-Alg films by scanning electron microscopy, thermogravimetry, X-ray diffraction and FTIR showed a highly homogeneous interpenetrated network scaffold without changes in the BC crystalline structure but with an increased amorphous phase. The main molecular interactions determined by FTIR between both biopolymers clearly suggest high compatibility. These results indicate that alginate plays a key role in the biophysical properties of the hybrid BC matrix. BC-Alg scaffold analysis by nitrogen adsorption isotherms revealed by the Brunauer-Emmett-Teller (BET) method an increase in surface area of about 84% and in pore volume of more than 200%. The Barrett-Joyner-Halenda (BJH) model also showed an increase of about 25% in the pore size compared to the BC film. Loading BC-Alg scaffolds with different amounts of doxorubicin decreased the cell viability of HT-29 human colorectal adenocarcinoma cell line compared to the free Dox from around 95-53% after 24h and from 63% to 37% after 48 h. Dox kinetic release from the BC-Alg nanocomposite displayed hyperbolic curves related to the different amounts of drug payload and was stable for at least 14 days. The results of the BC-Alg nanocomposites show a promissory potential for anticancer therapies of solid tumors.

Water Remediation: PVA-Based Magnetic Gels as Efficient Devices to Heavy Metal Removal

Scientific and technological researches are devoted to obtain materials capable of retaining different kinds of pollutants, contributing to contamination solutions. In this context, hydrogels have emerged as great candidates because of their excellent absorption properties as well as good mechanical, thermal and chemical properties. More specifically, ferrogels (magnetic gels) present the extra advantage of being easily manipulated by a permanent magnet. Here, we present the results derived from the application of ferrogels as efficient tools to extract heavy metal pollutants from wastewater samples. The gels were prepared following the method of freezing and thawing of a polyvinyl alcohol aqueous solution with magnetic nanoparticles coated with polyacrylic acid. Ferrogels were fully characterized and their ability to retain Cu2+ and Cd2+, as model heavy metals, was studied. Thus kinetics and mechanisms of adsorption were evaluated and modeled. The concentration of MNPs on the PVA matrix was key to improve the adsorption capability (approximately the double of retention is improved by the MNPs addition). The adsorption kinetics was determined as pseudo-second order model, whereas the Langmuir model was the most appropriate to explain the behavior of the gels. Finally reuse ability was evaluated to determine the real potential of these materials, the ferrogels demonstrated high efficiency up to about five cycles, retaining about 80–90% of their initial adsorption capability. All the results indicated that the materials are promising candidates able to compete with the commercial technology regarding to water remediation.

Biodegradable Polymeric Microparticles as Drug Delivery Devices

There are many disadvantages associated with the use of certain drugs. Therefore, therapeutically effective and patient-compliant drug delivery systems continuously lead researchers to design novel tools and strategies. Polymers are an excellent choice to obtain drug-carriers because of their stability and capability for high loading of many agents and their control over drug release kinetics and capability for modified their surface for attached ligands. In this work the behavior of polymers as drug carriers was studied. Salicylic acid loaded polymeric microparticles were synthesized and fully characterized showing that they are potential drug deliv-ery systems.