Optimizing Dual Fluorescent Analysis to Investigate the Toxicity of AgNPs in E. coli

The ever-increasing use of silver nanoparticles (AgNPs) carries potential ecotoxicological risks. For full risk assessment, E. coli cells harboring a plasmid with a constitutively expressed GFP gene under control of lac promoter (lac::GFP) are extensively utilized. Flow cytometry is an advanced technology usually applied to toxicological research for rapid, efficient, multi-parameter analysis of single cells. However, it is difficult to accurately and sensitively detect the toxicity of nanoparticles with flow cytometry due to the interference of aggregated nanoparticles. In this protocol, dual-fluorescence detection with a propidium iodide (PI)-lac::GFP assay is used to determine the toxicity of AgNPs and successfully discriminate the dead or fragilized bacteria from living bacteria and aggregated nanoparticles. © 2017 by John Wiley & Sons, Inc.