Preparation of 0.7SiO2·0.3CaO/PCL hybrid layers via sol–gel dip coating for the surface modification of titanium implants: characterization, bioactivity and biocompatibility evaluation

Abstract

When reactive coatings are applied to medical implants by means of the sol–gel dip-coating technique, the biological properties of the implant surface can be modified to simulate the properties of the surrounding tissues in such a way to provide a firm fixation of the implant. The aim of this study has been to modify the surface of titanium grade 4 (a material generally used in dental application) by dip coating with sol–gel synthesized organic/inorganic hybrid materials in order to improve their osseointegration ability. Different hybrids have been obtained, consisting of an inorganic 0.7SiO2·0.3CaO-based matrix in which a biodegradable polymer, poly-e-caprolactone (PCL), has been incorporated in different percentages. These materials, still in the sol phase, have been used to coat the titanium substrates by means of the dip-coating technique. Fourier transform infrared spectroscopy allowed the characterization of the materials and their classification as Class I hybrids, whereas a microstructural analysis of the obtained coatings, performed using scanning electron microscopy (SEM), detected that the PCL content affects film morphology. The potential applications of these coatings in the biomedical field have been evaluated by bioactivity and biocompatibility tests. SEM–EDS analysis of the coated titanium surfaces showed that the hydroxylapatite deposition occurs after 21 days of immersion in a simulated body fluid, an index of in vivo bone-bonding capability. Moreover, a WST-8 assay has shown that the vitality of fibroblast cells (3T3) seeded on the titanium specimens is higher when the coatings are applied and that the biocompatibility depends on PCL amount.