Binding Force and Site-Determined Desorption and Fragmentation of Antibiotic Resistance Genes from Metallic Nanomaterials

Interfacial interactions between antibiotic resistance genes (ARGs) and metallic nanomaterials (NMs) lead to adsorption and fragmentation of ARGs, which can provide new avenues for selecting NMs to control ARGs. This study compared the adsorptive interactions of ARGs (tetM-carrying plasmids) with two metallic NMs (ca. 20 nm), i.e., titanium dioxide (nTiO2) and zero-valent iron (nZVI). nZVI had a higher adsorption rate (0.06 min–1) and capacity (4.29 mg/g) for ARGs than nTiO2 (0.05 min–1 and 2.15 mg/g, respectively). No desorption of ARGs from either NMs was observed in the adsorptive background solution, isopropanol or urea solutions, but nZVI- and nTiO2-adsorbed ARGs were effectively desorbed in NaOH and NaH2PO4 solutions, respectively. Molecular dynamics simulation revealed that nTiO2 mainly bound with ARGs through electrostatic attraction, while nZVI bound with PO43– of the ARG phosphate backbones through Fe–O–P coordination. The ARGs desorbed from nTiO2 remained intact, while the desorbed ARGs from nZVI were splintered into small fragments irrelevant to DNA base composition or sequence location. The ARG removal by nZVI remained effective in the presence of PO43–, natural organic matter, or protein at environmentally relevant concentrations and in surface water samples. These findings indicate that nZVI can be a promising nanomaterial to treat ARG pollution.