Inactivation of the extracellular antibiotic resistance gene by titanium dioxide wrapped with carbon quantum dots under ultraviolet A irradiation

Abstract

This study aimed to mitigate extracellular antibiotic resistance genes (eARG) by employing a photocatalyst-based advanced oxidation process (AOP), renowned for inactivating ARG through interactions with reactive oxygen species (ROS). Nanocomposites were synthesized by coating nitrogen and sulfur co-doped carbon quantum dots (N,S-CQD) onto titanium dioxide (TiO2) and utilized them to inactivate ARG under UVA irradiation. The transformation assay indicated that 2 % N,S-CQD-TiO2 achieved the highest inactivation performance, reducing eARG transformation activity by over 4 log units, while 1 %, 4 %, and 6 % formulations achieved reductions of approximately 2-3 log units. This level of eARG inactivation was corroborated through qPCR analysis. Gel electrophoresis verified that eARG inactivation in the N,S-CQD-TiO2 nanocomposites stemmed from DNA strand damage. Additionally, ROS measurements confirmed that eARG inactivation by the N,S-CQD-TiO2 nanocomposite was due to the production of hydroxyl radicals. Photoluminescence analysis showed that N,S-CQD reduced TiO2 PL lifetime from 40 ns to 1.04 ns, indicating enhanced electron-hole separation and ROS generation. Finally, the N,S-CQD-TiO2 nanocomposite applied to livestock compost under 3.8 J/cm2 UVA irradiation achieved up to 4 log reductions in certain ARGs. In conclusion, this study suggests the potential applicability of the N,S-CQD-TiO2/UVA AOP system in environments where antibiotic contamination is a concern.