Comparative studies on measurement of membrane potential of bacterial cells treated with ZnO nanoparticles by Spectrofluorometry, fluorescence microscopy and flowcytometry

• Published in: Journal of microbiological methods 2020-06, Vol.173, p.105920-105920, Article 105920
• Main Authors: Khater, Maya, Khater, Sagar S., Gholap, Haribhau, Patil, Rajendra, Kulkarni, Gauri
• Format: Article
• Language: English
• Subjects: E. coli and S. aureus; Flowcytometry; Fluorescence microscopy; Membrane potential; Spectrofluorometry; ZnO nanoparticles
• ISSN: 0167-7012; 1872-8359
• DOI: 10.1016/j.mimet.2020.105920

Many methods are developed to assess antimicrobial action of ZnO nanoparticles (NPs). A large number of methods associated with the use of fluorescent probes are developed, including Spectrofluorometry, fluorescence microscopy, and cytometry. In this study, flowcytometry, Spectrofluorometry and fluorescent microscopy was used to measure membrane potential variation of E. coli and S. aureus cells treated with two different sizes of zinc oxide (ZnO) NPs and were compared with conventional methods. In order to estimate change in membrane potential, E. coli and S. aureus cells were treated with iopnophore agent carbonyl cyanide m-chlorophenylhydrazone (CCCP) and membrane potential was evaluated using fluorescent probe 3,3′-Diethyloxacarbocyanine, iodide (DIOC2(3)). All the three methods showed similar results and among these Spectrofluorometry was easy to use and inexpensive to assess the viability of bacterial cells via their membrane potential. [Display omitted] •Membrane potential studied by three different methods show similar results and are comparable.•Effect of ZnO NPs on membrane potential of E. coli and S. aureus is size dependent.•Effect of ZnO NPs on membrane potential of bacterial cells varies with species.•ZnO NPs causes lysis of bacterial cells as evident by cytoplasm leakage.•K+ ion leakage from cytoplasm is an indicator of depolarization of bacterial cell membrane due to effect of ZnO NPs.