Antibacterial Activity And Mechanism Of TiO₂-Ag-AgCl Photocatalyst Against Escherichia Coli

Bacterial pollution of water sources has become a global problem that damages the ecological environment and endangers public health.Traditional water disinfection methods generally have some problems,such as low degradation efficiency,limited scope of application,and secondary pollution.Therefore,it is necessary to develop efficient,energy-saving,and environment-friendly water treatment technology.TiO₂-based visible-light photocatalysts have attracted much attention due to its advantages of making full use of solar energy,low operating cost,and environmental protection.However,TiO₂ can only respond to ultraviolet light,so the catalytic activity of TiO₂-based visible light catalysts needs to be further improved.Ag/Ag X（x=Cl,Br,I）-based plasma induced photocatalysts have found to exhibit highly catalytic efficiency due to the SPR effect of Ag NPs.In view of this,TiO₂-Ag-Ag Cl photocatalyst was prepared in this study using by dopamine mediated biomimetic mineralization at room temperature.The morphology,crystal phase,element composition and optical properties of TiO₂-Ag-Ag Cl photocatalyst were characterized.The antibacterial activity and mechanism of TiO₂-Ag-Ag Cl photocatalyst against E.coli were studied at the cellular and molecular levels,in order to provide new ideas for the development of new antibacterial agents.The results are as follows:1.TiO₂-Ag-Ag Cl photocatalyst was successfully prepared,and found to had highly antibacterial activity against E.coli under visible light irradiation.Cycle test showed that TiO₂-Ag-Ag Cl could still kill 99%of E.coli after five cycles of use.Cytotoxicity test showed that TiO₂-Ag-Ag Cl had low cytotoxicity.When the material concentration reached 500μg/m L,58.8%of HUVEC cells survived,while the mortality of E.coil cells approached 100%.2.TiO₂-Ag-Ag Cl photocatalyst can effectively destroy E.coli biofilm.FESEM observation results showed that the untreated E.coli biofilm cells were dense and smooth,but with the increase of light time,E.coli cells gradually dispersed,deformed and even broken;and CV measurement results showed that with the increase of light time,cell membrane staining gradually became shallow,which further confirmed the above conclusion.3.TiO₂-Ag-Ag Cl photocatalyst can effectively destroy the structure of E.coli cells under visible light irradiation,and make the cells gradually deform,shrink and rupture with the increase of light time;the main active substances are h⁺and·O₂^-;Ag⁺in suspension has no obvious effect on E.coli.4.RNA-seq results showed that TiO₂-Ag-Ag Cl photocatalyst could up regulate the expression of ompx and omp A,and up regulate the expression of ahp C,ypfh and ompx.