Porous silicon biomaterials: PSi/Cyclodextrin drug delivery hybrids and PSi/Calcium phosphate bioceramic cell scaffolds

Resumen

Porous silicon (PSi) is an excellent biomaterial given its biocompatibility, biodegradability and bioresorbability. Nevertheless, it is necessary to adapt its properties depending on the specific application. In that sense, two new PSi-based biomaterials were developed to work in the field of drug delivery and cell scaffolds. PSi-biopolymer hybrids are attractive as drug delivery devices because they improve control over drug release kinetics and stability. According to this, two kinds of PSi, nano- and macro-, were modified by ß-cyclodextrin¿citric-acid in-situ polymerization. Both hybrids were characterized by microscopy and physicochemical techniques. Its biocompatibility was proved by means of L132 cells in vitro culture. Finally, both hybrids were tested as drug delivery systems with ciprofloxacin-base (antibiotic) and prednisolone (anti-inflammatory), in two mediums, distilled water and PBS. Results showed that both kinds of PSi/cyclodextrin hybrids, are functional for drug delivery applications. For the use PSi as cell scaffold in bone tissue engineering, deposition of calcium phosphate (CaP) in its hydroxyapatite (HAP) phase provides an added value. Within this context, the synthesis of CaP/PSi composites by means of two different techniques was developed: Cyclic Spin Coating (CSC) and Cyclic Electrochemical Activation (CEA). CSC and CEA consisted on alternate Ca and P deposition steps on PSi. Each technique produced specific morphologies and CaP phases using the same independent Ca and P stem-solutions at neutral pH. The brushite (BRU) phase was favored with CSC and the HAP phase was better synthesized using CEA. Analyses by RBS on CaP/PSi synthesized by CEA supported that, by controlling the CEA parameters, an HAP coating can be promoted. Besides, its PSi-CaP interface was studied by HAXPES. Biocompatibility was evaluated by bone-derived progenitor cells. Depending on the composite used to culture cells, a characteristic response of adhered cells was obtained. These results can be used for the design and optimization of CaP/PSi composites with enhanced biocompatibility for bone-tissue engineering. Keywords : Porous silicon Drug delivery ß-cyclodextrin/citric acid polymer Cell scaffolds Calcium phosphates