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

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 (DIOC(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.