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When soluble salts are used in the sol-gel processing of bioactive glasses, the resulting materials are not homogeneous. To produce homogeneous gel-glasses, a sol-gel method using all alkoxide precursors was developed. In this work the in vitro bioactivity of the new all-alkoxide gel-glasses is investigated. Three compositions in the system, CaO-P2O5-SiO2, were studied. Solid samples were soaked in Tris buffer and simulated body fluid (SBF), and the rate of formation of hydroxy carbonate apatite (HCA) on the surface of the glasses was measured by Fourier transform infrared spectroscopy. The solutions were analyzed before and after reaction by inductively coupled plasma. All compositions studied formed a hydroxy carbonate apatite (HCA) layer within 8 h in both test solutions. The HCA layer grew rapidly when SBF was used.

An apatite layer can he formed on pure gel-silica soaked in simulated body fluid. The rate of formation depends on solution parameters and sintering temperature of the gelsilica. In this study, the effect of the texture of the gel-silica on the rate of hydroxyapatite formation was investigated. The apatite formation was monitored by means of Fouriertransform infrared reflection spectroscopy as well as by the measurement of changes in the ion concentration of the fluid. The induction time for apatite nucleation on the gelsilica decreased as pore size and pore volume increased. The substrate parameters that affect nucleation are discussed and a mechanism that assumes pores as nucleation sites for hydroxyapatite is proposed.

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A new class of materials based on inorganic and organic species combined at a nanoscale level has received large attention recently. In this work the idea of producing hybrid materials with controllable properties is applied to obtain foams to be used as scaffolds for tissue engineering. Hybrids were synthesized by reacting poly(vinyl alcohol) in acidic solution with tetraethylorthosilicate. The inorganic phase was also modified by incorporating a calcium compound. Hydrated calcium chloride was used as precursor. A surfactant was added and a foam was produced by vigorous agitation, which was cast just before the gel point. Hydrofluoric acid solution was added in order to catalyze the gelation. The foamed hybrids were aged at 40 degrees C and vacuum dried at 40 degrees C. The hybrid foams were analyzed by Scanning Electron Microscopy, Mercury Porosimetry, Nitrogen Adsorption, X-ray Diffraction and Infra-red Spectroscopy. The mechanical behavior was evaluated by compression tests. The foams obtained had a high porosity varying from 60 to 90% and the macropore diameter ranged from 30 to 500 microm. The modal macropore diameter varied with the inorganic phase composition and with the polymer content in the hybrid. The surface area and mesopore volume decreased as polymer concentration increased in the hybrids. The strain at fracture of the hybrid foams was substantially greater than pure gel-glass foams.

In the present work we report the synthesis, characterization, and preliminary biocompatibility of polymer blends based on Chitosan and poly(vinyl alcohol) (PVA) with low degree of hydrolysis and chemically crosslinked by glutaraldehyde for potential application on skin tissue repairing. The microstructure and morphology of the blended hydrogels were characterized through Fourier Transform Infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM/EDX) analysis. Hydrogels were investigated by swelling as preliminary in vitro test using simulated body fluid. In addition, biocompatibility, cytotoxicity, and cell viability were assessed via MTT assay with VERO cell culture and cell spreading-adhesion analysis. It was found that by increasing the chitosan to PVA ratio, simulated body fluid uptake of the material was significantly altered. All the tested hydrogels have clearly presented adequate cell viability, non-toxicity, and suitable properties which can be tailored for prospective use in skin tissue engineering.

Tissue engineering is an important technique for regenerating diseased or damaged tissues. In tissue engineering, a highly porous artificial extracellular matrix or scaffold is required to accommodate cells and guide their growth and tissue regeneration in three dimensions. The choice of scaffolding material is crucial to the success of the technique. Bioactive glasses are an option as scaffold material for bone tissue engineering owing to their recognised osteoconductive and osteoinductive properties and controllable degradation rate. Resorbable 3D macroporous bioactive scaffolds have been produced by foaming sol-gel derived bioactive glasses with the aid of a surfactant. The foams exhibit a hierarchical structure, with interconnected macropores (10-600 mm) and mesopores (2-50 nm). The effects of processing variables on the structure and properties of the obtained bioactive glass foams are discussed in the present paper. The method is then applied to produce bioactive glass-polymer (polyvinyl alcohol) hybrid scaffolds with improved mechanical properties.