Enhancement of crystalline plane orientation in silsesquioxane-containing vaterite particles towards tuning of calcium ion release.

Siloxane-containing vaterite (SiV) particles with spherical- to discoidal-morphologies were selectively prepared by a CO2 gas carbonation process in a methanol-acetone mixed solvent; they are intended for application as osteogenic devices in bone tissue engineering. Moreover, the c/ab-face ratio of vaterite was successfully tuned through the selection of methanol-acetone volume fractions. The solvent increased the supersaturation of CO3 2- ions and accelerated the crystal growth along the ab-axis in the presence of silsesquioxane. The particles released soluble silica species and calcium ions upon soaking in physiological pH buffer solution, which are expected to genetically stimulate osteoblasts to enhance bone reconstruction. An initial calcium ion release from the particles significantly decreased from 3.1 to 1.6 mmol L-1 as the c/ab-face ratio increased, while the composition of the particle and release profiles of soluble silica remained consistent. This demonstrated the possibility of tuning the calcium ion release from SiV particles by controlling the degree of crystalline plane orientation.