Stability, Bioavailability, and Bacterial Toxicity of ZnO and Iron-Doped ZnO Nanopartides in Aquatic Media

摘要

The stability and bioavailability of nanopartides is governed by the interfacial properties that nanopartides acquire when immersed in a particular aquatic media as well as the type of organism or cell under consideration. Herein, high-throughput screening (HTS) was used to elucidate ZnO nanoparticle stability, bioavailability, and antibacterial mechanisms as a function of iron doping level (in the ZnO nanopartides), aquatic chemistry, and bacterial cell type. ξ-Potential and aggregation state of dispersed ZnO nanopartides was strongly influenced by iron doping in addition to electrolyte composition and dissolved organic matter, however, bacterial inactivation by ZnO nanopartides was most significantly influenced by Zn~(2+) ions dissolution, cell type, and organic matter. Nanoparticle IC_(50) values determined for Bacillus subtilis and Escherichia coli were on the order of 0.3-0.5 and 15-43 mg/L (as Zn~(2+)), while the IC~(50) for Zn~(20) tolerant Pseudomonas putida was always >500 mg/ L Tannic acid decreased toxicity of ZnO nanopartides more than humic, fulvic, and alginic acid, because it complexed the most free Zn~(2+) ions, thereby reducing their bioavailability. These results underscore the complexities and challenges regulators face in assessing potential environmental impacts of nanotechnology; however, the high-throughput and combinatorial methods employed promise to rapidly expand the knowledge base needed to develop an appropriate risk assessment framework.