Antimicrobial effect of silver zinc oxide (Ag-ZnO) nanocomposite particles

The antimicrobial effects of silver nanocomposite particles (Ag-ZnO NC) on microorganisms, the antimicrobial mechanism and applications in medical devices are not yet clear. Stable Ag-ZnO NC were prepared and their morphological sizes and shapes were characterized by scanning electron microscopy. The effect of Ag-ZnO NC was tested on Bacillus thuringiensis, Escherichia coli and Pseudomonas aeruginosa in antibacterial tests including growth kinetics, antimicrobial susceptibility (disc diffusion) and minimal inhibitory concentration (MIC). Different concentrations of nanocomposites (i.e. 10, 20, 50,100, and 200 mu g) showed concentration-dependant efficacy on all three tested microorganisms. E. coli was fairly sensitive in 200 mu g of NC, forming a similar to 15mm inhibition zone; followed by B. thuringiensis, having similar to 9mm of inhibition zone, while P. aeruginosa, a pathogenic bacterium, showed negligible inhibition zone with Ag-ZnO NC. Growth of E. coli under Ag-ZnO NC treatment was significantly delayed with an extended lag phase of 2hrs and 30mins. Scanning electron microscopy confirmed the bacteriostatic effect of Ag-ZnO NC, which was manifested in cell division arrest with significant cell elongations compared to the control. The free radical generation effect of Ag-ZnO NC was tested against all these organisms. The results suggest that Ag-ZnO NC can be used effectively against microbial growth. This may be of use in diverse medical devices for antimicrobial control and can be a proper substitute for antibiotics in curing human health.