Preparation of bioactive microspheres of organic modified calcium silicates through sol–gel processing

Bioactive ceramics show specific biological activity, a bone-bonding ability, and are used as bone-repairing materials. Particles of bioactive ceramics may be used as fillers for fabricating bioactive composites where bioactive fillers are dispersed in a polymer matrix. Chemical bonding between the filler and the organic matrix requires an effective organic modification of the bioactive filler. Previous studies have reported that inorganic glasses in the CaO–SiO₂ system act as fundamental components showing bioactivity, as they show a high potential to form bone-like apatite after exposure to a body fluid. Therefore, organically modified microspheres composed of CaO–SiO₂ gels can be useful as bioactive fillers to produce bioactive composites. In this study, the conditions for the preparation of organically modified gels composed of CaO–SiO₂ were investigated using sol–gel processing of tetraethoxysilane, calcium nitrate tetrahydrate and silane coupling agents (SCAs), such as 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane (GPS), along with polyethyleneglycol (PEG). Spherical particles with diameter of 2–3 μm were obtained when adding the SCAs, except for GPS with PEG. Incorporation of the SCAs was confirmed using Fourier transform infrared spectroscopy. All the samples prepared with the SCAs formed bone-like apatite on their surfaces in a simulated body fluid within a period of 1 day. These results indicate that bioactive microspheres of organically modified CaO–SiO₂ gels can be obtained using sol–gel processing with SCAs.