Antimicroorganism activities comparison among ZnO, TiO2, MgO and SiO2 nanoparticles suspensions at different pH values

This work investigated the antimicroorganism activities of ZnO, TiO₂, MgO and SiO₂ nanoparticles suspensions at different pH values. In this work, E. coli was used as model bacteria to test the antimicroorganism activities of these nanoparticles suspensions. Growth curves investigation with and without these nanoparticles suspensions was used to examine the antimicroorganism activities. The results demonstrate that ZnO and TiO₂ suspensions have an inhibiting effect against the growth of E. coli bacterial cells at all pH levels. MgO suspensions have a weak or no antibacterial activity at a pH value of 5, but have some extent of promoting effect at pH 7 and 11. SiO₂ suspensions have very little effect on the growth of E. coli bacterial cells at all pH values. One of the reasons for the difference of antimicroorganism activities among these nanoparticles suspensions at different pH values may be related to the electrostatic forces between nanoparticles and bacterial cells.