Methodology to evaluate the antimicrobial effectiveness of UV-activated TiO2 nanoparticle-embedded cellulose acetate film

Abstract

TiO2 nanoparticle (NP)-embedded cellulose acetate (CA) films were prepared using solution casting method and found that it can inactivate Escherichia coli O157: H7 under UV-A light illumination. This study investigated the microbial inactivation efficacy of this film under several practical application scenarios: (1) direct contact with bacteria which were located either above or beneath the film; (2) with or without contact with bacteria; (3) contact with dried bacterial inoculum; and (4) submerged in contaminated water. Results showed that antimicrobial performance of TiO2 NP-embedded CA film varied depending application scenarios. For Scenario 1, the reductions were 1.1 log CFU/ml above and 0.5 log CFU/ml beneath the film after 2 h illumination. For Scenario 2, the reductions were 1 log CFU/ml with direct contact and 0.6 log CFU/ml without direct contact after 6 h exposure. For Scenario 3, the reduction was 3.5 log CFU/ml after 6 h. For scenario 4, the reduction was 5.2 log CFU/ml after 6 h. This study demonstrated the crucial role of contact between the bacterial cells and NP-embedded surface to achieve microbial inactivation. Results of this study suggest that the most effective applications of TiO2 NP-embedded polymer film can be obtained when in direct contact with liquid inoculum or contaminated solutions.