Enhancing the Antibacterial Activity of Zinc-Based Layered Double Hydroxide Nanoparticles in the Presence of UV A Light

High Resolution Image Download MS PowerPoint Slide Pristine zinc-based layered double hydroxides (LDHs) possess remarkable antibacterial properties. The antibacterial activity of zinc-based LDHs could be explained by three possible mechanisms: (1) direct contact interactions between the LDH and bacterial surfaces, (2) release of antibacterial Zn 2+ aq ions, and (3) generation of reactive oxygen species (ROS) by LDHs in response to irradiation by a suitable light source. In this work, the potential contribution of ROS generation in the antibacterial activity of ZnAl LDH nanoparticles (NPs) was determined by comparing their effect against Gram-positive Staphylococcus aureus bacteria in the presence and absence of UV A irradiation (λ = 365 nm, irradiation period = 4 h). The bactericidal efficacy of ZnAl LDH NPs was significantly enhanced in the presence of UV A light. The bactericidal activity was hindered in the presence of histidine acting as a ROS scavenger and giving indirect evidence of the role of ROS. Moreover, Fourier-transform infrared spectroscopy revealed denaturation and suppression of several structural components in S. aureus cells exposed to ZnAl LDH NPs under dark conditions and in the presence of UV A radiation, with more pronounced alterations for the latter. The impacts of such alterations on the topographical properties of S. aureus cells were determined by atomic force microscopy imaging. Treated cells with ZnAl LDH NPs were completely deformed and exhibited increased roughness, especially upon treatment in UV A conditions. All these results suggest the presence of a dual antibacterial effect between ZnAl LDH NPs and their generated ROS to provide amplified antibacterial activity.