Analysis of the structure and bioactivity on SiO₂ film cured from perhydropolysilazane

Bioactive ceramics, one of the most popular biomaterial, is now widely used for bone-repairing. However, its application is limited to less loaded regions because of its low fracture toughness. We focused on Perhydropoh/silazane (PHPS) which is an organosilicate polymer consisting of cyclic (SiH ₂-NH)_n units. PHPS converts easily to silicon dioxide by heat-treatment lower than 150°C and is capable of compounding with low-melting polymers. By compounding with such materials SiO₂ film bearing several mechanical properties can be cured from PHPS. In this study, SiO₂ films were cured under various conditions. In order to investigate the existence of Si-OH, inducing the nucleus formation of apatite, sample surfaces were characterized by Fourier transform infrared reflection (FT-IR). Bioactiveness of each samples was tested by immersing in Simulated body fluid (SBF), solution which ion concentration is nearly equal to that of human blood plasma, for seven days. From the immersion tests, some samples showed bioactivity. Zeta potential of each samples were also measured. The dissolution of SiO₂ films under immersion were examined by Atomic absorption spectroscopy (AAS). From these results, SiO₂ films of (i) relatively less Si-H, witch repels the Ca ion bonding, (ii) surface Si-OH existing without condensation, (iii) Si-O-2NBO (Non-bridging oxygen) containing siloxane structure witch encourages the dissolution of silicate ion, showed bioactivity.