In vitro evaluation of bactericidal efficacy, cytotoxicity and genotoxicity of combined negative ions and ozone treatment.

To achieve safe and highly efficient sterilization at low concentrations of ozone, we developed a novel sterilization device that generates negative ions and ozone (NIO3) through its integrated electron-emitting negative ion generator and corona discharge ozone generator. This device allows independent control of negative ion and ozone concentrations. The bactericidal activity and tolerability of gas-phase exposure using this device was studied. Bactericidal effects were quantified against Escherichia coli after 60 min exposure under controlled chamber conditions. Under standard NIO3 conditions (2 × 106 ions/cm3 and 0.05 ppm ozone) with a controlled downflow, the survival rate of E. coli decreased to 0.23% (corresponding to a 99.7% reduction), and the survival rate fell to 0.12%, with 8× standard NIO3 conditions without downflow, which is close to the assay detection limit. No statistically significant effects on cytotoxicity and genotoxicity were observed in A549 cells exposed under submerged conditions up to 10× standard NIO3 conditions as assessed by MTT assay, comet assay, and micronucleus test. These in vitro bactericidal and biocompatibility findings demonstrate that NIO3-mediated surface decontamination is a promising approach under the evaluated chamber conditions.