A Thermoresponsive injectable drug delivery system of chitosan/ß-glycerophosphate with gellan gum/alginate microparticles.

The development of new Drug Delivery Systems (DDS) by incorporating microparticles within hydrogels can prolong the release rate of drugs and/or other bioactive agents. In this study, we combined gellan gum/alginate microparticles within a thermoresponsive chitosan (Ch) hydrogel with ß-Glycerophosphate (ß-GP), designing the system to be in the sol state at 21 °C and in the gel state at 37 °C to enable the injectability of the system. The system was in the sol state between 10 °C and 21 °C. Higher concentrations of ß-GP (0, 2, 3, 4, 5 w/v%) and microparticles (0, 2 and 5 w/v%) allowed a faster sol-gel transition with higher mechanical strength at 37 °C. However, the sol-gel transition was not instantaneous. The release profile of methylene blue (MB) from the microparticles was significantly affected by their incorporation in Ch/ß-GP hydrogels, only allowing the release of 60-70 % of MB for 6 days, while the microparticles alone released all the MB in 48 h. The proposed system did not present cytotoxicity to VERO cell lines as a preliminary assay, with the Ch/ß-GP/GG:Alg having >90 % of cellular viability. The proposed Ch/ß-GP system proved to have a delaying effect on drug release and biocompatible properties, being a promising future DDS.

Evaluation of smart gelatin matrices for the development of scaffolds via 3D bioprinting.

Throughout history, different techniques have been used for the development of scaffolds for Tissue Engineering. Among them, three-dimensional (3D) printing for this application has been recently enhanced due to its ease in defining the structure of the material. In this sense, a novel potential alternative could be the development of a three-part device whose leading utility is to improve the introduction of the scaffold in a bioreactor. Thus, the device consists of a polycaprolactone support on which smart gelatin (GE) matrix, and finally, on top, a collagen (C) scaffold. This gelatin matrix is included to integrate the scaffold into the support, but once both are assembled, it must be removed, leaving only the support and the scaffold. Thus, in the present work, a small gelatin matrix has been evaluated. To this end, matrices with different gelatin percentages were studied, evaluating their mechanical and morphological properties at different temperatures (22 and 37 °C) to control their deposition and elimination. The results show the high application of this smart matrix for the development of scaffolds via 3D bioprinting for Tissue Engineering.

Crosslinking of hybrid scaffolds produced from collagen and chitosan.

The development of biodegradable scaffolds able to support cell growth has recently become of great importance. Therefore, the main objective of this work was the development of hybrid scaffolds made from the mixture of two biopolymers (collagen and chitosan) and the comparison of the effect of glutaraldehyde as crosslinking agent with three different crosslinking methods (chemical: genipin; physical: temperature and enzymatic: transglutaminase) in order to look for a promising candidate to substitute it. To achieve this purpose, the mechanical properties, structure, porosity, degree of crosslinking and swelling of the different scaffolds were assessed. The best ratio of biopolymers (collagen:chitosan) to form hybrid scaffolds was 1:1, which improve their mechanical and morphological properties compared to unitary scaffolds (only collagen or chitosan). In addition, the incorporation of 10% w/w transglutaminase (crosslinking agent) with respect to the mass of biopolymers made these scaffolds a good structure for the growth and proliferation of cells.