Selective Adsorption and Photocatalytic Degradation of Extracellular Antibiotic Resistance Genes by Molecularly-Imprinted Graphitic Carbon Nitride

Abstract

There is a growing need to mitigate the discharge of extracellular antibiotic resistance genes (ARGs) from municipal wastewater treatment systems. Here, molecularly-imprinted graphitic carbon nitride (MIP-C₃N₄) nanosheets were synthesized for selective photocatalytic degradation of a plasmid-encoded ARG (<i>bla</i>_NDM-1, coding for multidrug resistance New Delhi metallo-β-lactamase-1) in secondary effluent. Molecular imprinting with guanine enhanced ARG adsorption, which improved the utilization of photogenerated oxidizing species to degrade <i>bla</i>_NDM-1 rather than being scavenged by background nontarget constituents. Consequently, photocatalytic removal of <i>bla</i>_NDM-1 in secondary effluent with MIP-C₃N₄ (<i>k</i> = 0.111 ± 0.028 min^-1) was 37 times faster than with bare graphitic carbon nitride (<i>k</i> = 0.003 ± 0.001 min^-1) under UVA irradiation (365 nm, 3.64 × 10^-6 Einstein/L·s). MIP-C₃N₄ can efficiently catalyze the fragmentation of <i>bla</i>_NDM-1, which decreased the potential for ARG repair by transformed bacteria. Molecular imprinting also changed the primary degradation pathway; electron holes (h⁺) were the predominant oxidizing species responsible for <i>bla</i>_NDM-1 removal with MIP-C₃N₄ versus free radicals (i.e., ·OH and O₂^-) for coated but nonimprinted C₃N₄. Overall, MIP-C₃N₄ efficiently removed <i>bla</i>_NDM-1 from secondary effluent, demonstrating the potential for molecular imprinting to enhance the selectivity and efficacy of photocatalytic processes to mitigate dissemination of antibiotic resistance from sewage treatment systems.