The Biological Effect Of Nano ZnO To Escherichia Coli

Nanometer zinc oxide（Nano ZnO） is one of the most widely used nano material and has good photoelectric properties and unique antibacterial. Recently, the acterial activity and mechanism of Nano ZnO are becoming a hot research topic in the region of nanobiomaterials. In this work, we explored the antibacterial activity and mechanism of Nano ZnO toward Escherichia Coli（E.coli） in the lab environment. Here, we modified the surface of Nano ZnO with three kinds of long chain organic molecules that had different electrical properties, and then investigated the influence of surface charge of Nano ZnO on its antibacterial properties. The main results are as follows:（1） The concentration of dissolved zinc ions(Zn²⁺) in LB culture medium was detected and the saturated solubility of Zn²⁺ was about 55 mg/L. Throughcontrast experiments and dark experiments, the dissolved Zn²⁺ was proved to be the main mechanism of the antibacterial activity of Nano ZnO. In order to further verify this result, theendogenous fluorescence, cell membrane potential and total amount of nucleic acid and protein of E.coli under125 mg/L Nano ZnO and 50 mg/L Zn²⁺ were also detected and analyzed. The results confirmed that the dissolved Zn²⁺ played a major role in the Nano ZnO antibacterial mechanism towards E.coli. Through the action mechanism of adhering to the cell wall, changing the membrane potential as well as damaging the DNA and protein.（2） The surface of Nano ZnO was modified with hexadecyl dimethyl acetoxy quaternary ammonium salt（QAC）, oleic acid（OA） and octadecane diacid（ODA） through the esterification reaction between carboxyl and the hydroxyl. The best reaction mass ratio of QAC, OA, ODA and Nano ZnO was 1%, 32% and 16% respectively. Characterization results proved that the QAC, OA and ODA were modified to the Nano ZnO surface successfully and the meanwhile the surface were positively charged, uncharged and negative charged, respectively. Antibacterial experiments showed that the Nano ZnO with uncharged surface exhibited higher antibacterial activity towards E.coli. However, the presence of surface chargeon Nano ZnO inhibited its antimicrobial properties.The research above laid a foundation to understand the antibacterial mechanism of Nano ZnO and had an important guidance for its application.