No abstract

Metal–carbon hybrid materials have shown promise as potential enzyme mimetics for antibacterial therapy; however, the effects of metal states and corresponding antibacterial mechanisms are largely unknown. Here, two kinds of copper/carbon nanozymes were designed, with tuned copper states from Cu0 to Cu2+. Results revealed that the copper/carbon nanozymes exhibited copper state-dependent peroxidase-, catalase-, and superoxide dismutase-like activities. Furthermore, the antibacterial activities were also primarily determined by the copper state. The different antibacterial mechanisms of these two copper/carbon nanozymes were also proposed. For the CuO-modified copper/carbon nanozymes, the released Cu2+ caused membrane damage, lipid peroxidation, and DNA degradation of Gram-negative bacteria, whereas, for Cu-modified copper/carbon nanozymes, the generation of reactive oxygen species (ROS) via peroxidase-like catalytic reactions was the determining factor against both Gram-positive and Gram-negative bacteria. Lastly, we established two bacterially infected animal models, i.e., bacteria-infected enteritis and wound healing, to confirm the antibacterial ability of the copper/carbon nanozymes. Our findings provide a deeper understanding of metal state-dependent enzyme-like and antibacterial activities and highlight a new approach for designing novel and selective antibacterial therapies based on metal–carbon nanozymes.

The presence of sulfonamide antibiotics in aquatic environments has been recognized as an issue warranting consideration. In this study, we evaluated multiwalled carbon nanotubes (MWNT) as a potential effective adsorbent for removal of two sulfonamide antibiotics, sulfapyridine and sulfamethoxazole, from aqueous solutions. Nonporous, functionality-free graphite was included as a comparative adsorbent. Despite the very low hydrophobicity, the two sulfonamides adsorbed strongly to MWNT and graphite, a fact attributed to pi-pi electron coupling with the graphene surface of the adsorbent. For both sulfonamide antibiotics, similar patterns of pH-dependent adsorption were observed between MWNT and graphite, implying the predominance of graphene structures for the adsorption to MWNT. Moreover, the observed pH effects on adsorption indicate that the protonated neutral form of sulfonamide adsorbs much more strongly than the deprotonated anionic counterpart does. The effects of ionic strength (NaCl and CaCl2) and the presence of a dissolved soil humic acid on adsorption of the two antibiotics to MWNT and graphite were also assessed. Ring current-induced 1H NMR upfield chemical shifts further verified face-to-face complex formation between neutral sulfamethoxazole and model pi-electron donor compounds (naphthalene, phenanthrene, and pyrene) in solution.