Effect of ion species on apatite-forming ability of silicone elastomer substrates irradiated by cluster ion beams

Indwelling catheters made of silicone elastomers sometimes cause serious infections owing to their poor biocompatibility. It is believed that these infections can be prevented by coating the silicone surface with apatite, which has excellent biocompatibility. If the surface of the silicone elastomer is in advance modified to have an apatite-forming ability, apatite can be coated on the modified silicone surface by soaking it in an aqueous solution such as a simulated body fluid (SBF) supersaturated with respect to apatite. In this study, silicone substrates were irradiated by four types of ion beams (Ar cluster, Ar cluster and monomer (Ar CM), O2 cluster, and O2 cluster and monomer (O2 CM) ion beams) at an acceleration voltage of 7 kV and a dose of 1 × 1015 ions/cm2, and subsequently soaked in CaCl2 solution. The apatite-forming abilities of the substrates were examined using a metastable calcium phosphate solution whose ion concentration was 1.5 times that of SBF (1.5 SBF). Silicon oxide (SiOx) clusters were formed on the silicone surface and the hydrophilicity of the substrates was improved by the irradiation, irrespective of the ion species used. The irradiation with O2 CM ion beams resulted in the highest apatite-forming ability among the analyzed ion beams.