Synergistic effect of silanol group and calcium ion in chitosan membrane on apatite forming ability in simulated body fluid

A chitosan membrane modified with silanol groups and calcium ions on its surface and in its structure, respectively, was newly developed and evaluated for the potential application as a bioactive-guided bone-regeneration membrane. The chitosan membrane, which contained calcium nitrate tetrahydrate, was prepared and further subjected to surface modification with 3-isocyanatopropyl triethoxysilane (IPTS) following hydrolysis with HCl solution. As control, chitosan membranes which contained only calcium nitrate tetrahydrate and modified with only silanol groups were prepared, respectively. Three membranes were exposed to simulated body fluid (SBF) for a period ranging from 3 h to 7 days. The SBF exposure led to the deposition of a layer of apatite crystals on the surface of the chitosan membrane modified with silanol groups and calcium ions, while those modified with only calcium ions or silanol groups did not show the apatite-forming ability. It implies that the silanol groups and calcium ion acted together in a synergistic fashion in the formation of apatite crystals; the silanol groups and calcium ions acted as the nucleation sites and accelerator for the formation of apatite crystals, respectively. Therefore, this new chitosan membrane is likely to have a potential for the application as a bioactive guided bone regeneration membrane because of its apatite-forming ability in the SBF.