Study On Antibacterial Effect And Mechanism Of Nano-Materials

Taking five bacteriums and two yeast as target strains, inhibition and antibacterial effect of two nano-materials were tested, and the killing procedure of target strains were observed by ESEM, and sterilizing mechanism were known in this paper.The antibacterial effect of nano-Ag and nano-TiO₂ were qualitatively test by inhibition zone, that proofed two materials have the broad-spectrum antibacterial effect. The MIC and MBC of nano-Ag and nano-TiO₂ have been tested. Both of them are roughly same. The MIC on bacterium and yeast is 200μg/L and 400μg/L, respectively. The MBC on bacteriums and yeast is 107 cfu/mL and 105cfu/mL, respectively.Inhibitory action of nano-Ag and nano-TiO₂ on G+ bacterium is the best, followed by the effect on bacillus and G+ bacterium, and its effect on yeasts is the weakest relatively. I think it has relations with its different structure of cell wall and membrane. The antibacterial effect of two nano-materials is direct proportion with concentration and time, the more the concentration and time is high, the more the rate of bacteriostasis is high. When the concentration is 200μg/L, the bacteriums would be to kill in 18 hours, but the concentration is 400μg/L if you want to kill the yeasts in the same conditions.In addition, the smaller the particle of nano-Ag is, the better the rate of bacteriostasis is. There is very conspicuous disparity between Ag+ ion and nano-Ag, so the sterilizing mechanism of two nano-materials should not be the same. The nano-TiO₂ has good stability under heat treatment.The killing procedure of target strain was observed by ESEM. The process of nano-materials photocatalysisinactivation of bacterium begins with destroying the structure of cell wall by the free radical TiO₂ produced. These free radical make the cell wall disruptive and disrepairabl, the plasmalemma disassemble, and then it chisel in the cell, destroy the reticulum and the inner structure which make the cytoplasm coacervateand cause the extravasation of entocyte to form cavitate cells.