Thin film of low-crystalline calcium phosphate apatite formed at low temperature.

Surface modification of biomaterials to improve biocompatibility without changing their bulk properties is desired for many clinical applications and has become an emerging technology in biomaterial research and industry. In the present study, a simple method of coating the solid surfaces of metals, organic tissue matrices, glasses, inorganic ceramics as well as organic polymers with a thin film of low-crystalline apatite crystals (LCA) was developed. Acidic solution containing calcium and phosphate ions was neutralized with alkaline solution to form calcium phosphate precipitates at low temperature. Precipitates of solid calcium phosphate particles were, then, removed by filtration. Concentration of free ions in the filtered ion solution which were not involved in the formation of calcium phosphate precipitate was high enough to induce the heterogeneous nucleation on the solid surfaces at low temperature. Thin layers of calcium phosphate crystals were formed on the surfaces of metals, glasses, inorganic ceramics, organic polymers including hydrophobic ones, and biological tissue matrices with this solution. The thin layer of crystals consisted of poorly crystalline calcium phosphate apatite crystals which contain high amount of labile ions like bone crystals and did not dissolve in the physiologic solutions. Various cells attached to this crystal layer and proliferated well.