title: Dosage- and time-dependent antibacterial effect of zinc oxide nanoparticles determined by a highly uniform SERS negating undesired spectral variation.
abstract: Massive production of nanomaterials poses a high risk to environmental ecology and human health. However, comprehensive understanding of nanotoxicity is still a major challenge due to the limitations of assessment methods, especially at the molecular level. We developed a new, sensitive, and robust fingerprinting surface-enhanced Raman spectroscopy (SERS) approach to interrogate both dose- and time-dependent phenotypic bacterial responses to zinc oxide nanoparticles (ZnO NPs). SERS enhancement was provided by biocompatible Au NPs. Additionally, a novel vacuum filtration-based strategy was adopted to fabricate bacterial samples with highly uniform SERS signals, ensuring the acquisition of robust and independent spectral changes from ZnO NPs-impacted bacteria without undesirable spectral variations. Combined with multivariate analysis, clear and informative spectral alteration profiles were obtained. Much greater alterations were found in low-dose ranges than high-dose ranges, indicating a reduction in the bioavailability of ZnO NPs with doses. Time-resolved bacterial responses provided important information on toxic dynamics, i.e., rapid action of ZnO NPs within 0.5 h was identified, and ZnO NPs at low doses and long exposure time exerted similar effects to high doses, indicating the concerns associated with low-dose exposure. Further analysis of biochemical changes revealed metabolic activity decrease over both incubation time and doses. Meanwhile, a short-term protection strategy of bacteria by producing lipid-containing outer membrane vesicles to mitigate the cell of toxic NPs was suggested. Finally, Zn(2+) ions released from NPs were demonstrated to be irrelevant to bacterial responses on both dose and time scales. The new SERS methodology can potentially profile a large variety of toxic NPs and advance our understanding of nanotoxicity. Graphical Abstract A highly uniform SERS signal of bacteria negating undesired spectral variation via a novel vacuum filtration-based strategy, combined with multivariate PCA-LDA analysis, was utilized to interrogate both dose- and time-dependent antibacterial effect of zinc oxide nanoparticles, and can be extended to a variety of other toxic nanoparticles.
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Jimei road 1799, Xiamen, Fujian, 361021, China.
authors.forename: Bifeng
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Jimei road 1799, Xiamen, Fujian, 361021, China. lcui@iue.ac.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Cui
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Jimei road 1799, Xiamen, Fujian, 361021, China. kszhang@iue.ac.cn.
authors.forename: Kaisong
authors.initials: K
authors.lastname: Zhang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D013059:Spectrum Analysis, Raman / Q000379:methods*; D015034:Zinc Oxide / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D015034:Zinc Oxide
keywords: Antibacterial effect; Dose-dependent; Nanotoxicity; Surface-enhanced Raman spectroscopy; Time-dependent; ZnO nanoparticles