Efficient inactivation of Staphylococcus aureus by silver and copper loaded photocatalytic titanate nanotubes

One dimensional titanate nanotubes (TNTs) were synthesized by microwave assisted alkaline hydrothermal process. The process was followed by UV-photodeposition of Ag and Cu on the surface of TNTs to enhance the photocatalytic activity in visible light spectrum. The loading of Ag and Cu (single and combination mode) offered a new insight to inactivate multi-drug resistant micro-organisms. The antibacterial properties of these samples were studied on Gram positive bacteria, Staphylococcus aureus (S. aureus) using well diffusion method. The TNTs with Ag and Cu loading showed a clear zone of inhibition after overnight incubation of S. aureus. The bacterial inactivation efficiency of nanoparticles in the visible light was further analyzed by kill kinetics. TNTs with Ag and/or Cu loading showed a significant reduction in bacterial growth. Cu co-loaded with Ag sample showed the highest inactivation efficiency within 90 min of visible light irradiation. To elucidate the mechanism of bactericidal properties of samples under visible light irradiation, the formation of reactive oxygen species (ROS), particularly, superoxide radical anion was determined by nitro blue tetrazolium (NBT) assay and the protein degradation by each samples were measured. Based on overall results, it was observed that the Cu co-loaded with Ag on TNTs samples were found to be more effective as compared to either Ag or Cu loaded TNTs. It provides new avenues for utilizing the combination of Cu and Ag for enhancing the antimicrobial efficacies for different nanoparticles. Keywords: Titante nanotubes, Staphylococcus aureus, Antibacterial, Photocatalytic inactivation, Reactive oxygen specie