Effects of pH and temperature on antibacterial activity of silver nanoparticles

Silver nanoparticles (SNPs) have received considerable attention owing to their attractive physicochemical properties, such as small size effect, quantum tunnel effect, surface effect et al. SNPs have recently been reported to be a promising antimicrobial material showing strong inhibition for a wide range of microorganisms. SNPs have currently been used as a new antimicrobial material in different areas from refrigerator surface coating, food packaging material modification to medical device treatments. For wide range applications of SNPs, their stable antimicrobial effects under different conditions need to be confirmed or investigated to guide/limit the use of these new materials. Here we report some antibacterial activity changes of SNPs after different treatments, including being exposed to extreme pH before antagonistic assays, and co-cultured at different temperature. A pathogenic microorganism-Escherichia coli O157:H7 was employed as an indicator, and the standard microorganism co-culture method was used for the evaluation. Results showed that the antibacterial activity of SNPs decreased at low temperature, as well as after exposed to low pH.