Cytotoxicity of medical materials sterilized with vapour-phase hydrogen peroxide

A new sterilization system using vapour-phase hydrogen peroxide (VPHP) was recently developed. The cytotoxicity of various medical materials sterilized by the VPHP sterilization system was investigated. After VPHP sterilization, polystyrene, polyurethane (PU8), blend material of silicone and polyurethane (Sil/PU6), poly(methyl methacrylate) (PMMA), fluorosilicone acrylate and poly(2-hydroxyethyl methacrylate) (HEMA) showed strong cytotoxicity, whereas polyethylene and polypropylene did not. Although the cytotoxic potential of most materials is reduced by extension of the aeration time, HEMA and PMMA still retained strong cytotoxicity after 12 h aeration. Addition of catalase to the cell culture eliminated the cytotoxicity of sterilized polystyrene and PU8. Hydrogen peroxide (H2O2) residues remaining in the sterilized materials were determined. Large amounts of H2O2 (5.1-186 micrograms) were detected in HEMA, PU8, Sil/PU6 and PMMA. In contrast, silicone and polyethylene contained low levels of H2O2. The amounts of residual H2O2 in the materials decreased with increasing aeration time, but the elimination rate of H2O2 differed among the test materials. The cytotoxic potential of the VPHP-sterilized materials correlated with the amounts of residual H2O2 present. These results indicated that the cytotoxicity of VPHP-sterilized materials was caused by the residual H2O2. To generalize the developed VPHP sterilization system for various medical devices, it is important to validate the aeration of materials for removal of cytotoxic residuals.