Autotoxicity Of Biogenic Cadmium Sulfide Nanoparticles To Synthetic Cells Under Photoexcitation Conditions

Cadmium sulfide nanoparticles(CdS NPs)are an important semiconductor.Because of their good photoelectric properties and chemical stability,they have important applications in many fields such as analytical chenistry,biomedicine and fluorescence imaging.However,CdS NPs not only have heavy metal toxicity and nanoparticle toxicity.Under visible light irradiation,semiconductor CdS NPs can form electron-hole pairs,and photogenerated electrons can generate superoxide anion radicals with oxygen.The released oxidative holes can also cause a sharp increase in intracellular oxidative pressure,causing serious damage to the cell.In this article,the toxicity mechanism of biogenic cadmium sulfide to its synthetic cells under the condition of light excitation was studied.In this study,E.coli CD-2 strain was selected to synthesize CdS NPS with cadmium chloride and L-cysteine as cadmium and sulfur sources.Analysis of biosynthetic nanoparticles by transmission electron microscopy,selected area electron diffraction analysis,X-ray energy spectrum analysis,X-ray diffraction,and electrochemical analysis techniques.The results showed that the CdS NPS was located in the cell,and the diameter of a single nanoparticle is approximately 4 nm.The CdS NPS synthesized by this bacteria have good biocompatibility.The selected area electron diffraction analysis of biosynthetic CdS NPs showed that they have polycrystalline characteristics,which confirmed the formation of the cubic structure of CdS.X-energy spectrum analysis found that the nanoparticles in the cell are composed of two elements:Cd and S,the ratio is about 1:1.X-ray diffraction analysis confirms that the crystal type of the CdS NPs is cubic.The results of electrochemical analysis indicate that the biosynthetic CdS NPS has photocurrent.Enzymatic methods are used to detect the activity of cell antioxidant enzymes such as superoxide dismutase and lactate dehydrogenase under light excitation conditions.The eneray metabolism of cells is detected by measuring the content of ATP and the content of coenzyme ?NAD+/NADH in the cell.Use protein carbonylation as an indicator to detect the oxidative pressure inside the cell.The results show that CdS NPs can be light-excited under light coditions,and the resulting light-excited toxicty can inhibit cell growth,metabolism and vitality.The oxidative pressure faced by cells that synthesiz CdS NPs increases sharply after light exposure.The protein carbonyl content indicated that the cells were subjected to strong oxidative pressure under light excitation conditions The LDH and SOD enzyme activity and plate count experiments showed that the cell rupture increased,and the SOD enzyme acivity decreased,bur not all died.The determination of ATP and coenzyme ? NAD+/NADH content indicates that the eneray metabolism of cells and the reducing power in cells are affected.The changes in gene expression of CdS NPs synthesizing bacteria under light-excited conditions were detected by fluorescence quantitative PCR.The results showed that compared with untreated cells,although the expression of sodA and katE genes decreased under light-excited conditions,the antioxidant defense system in the cells still in effect,the expression of grxA gene and trxC gene has increased significantly.The low levels of ef-tu and mutS in terms of protein synthesis and DNA repair gene expression prove that the metabolic activity of cells is very low.However,dnaK has a higher expression level of protein folding repair genes,which means that cells have a large number of proteins that need to be folded and repaired.The metabolic level and vitality of the bacteria and the gene expression results all show that in the presence of the sacrificial agent,the sacrificial agent is compounded with oxidative cavities,alleviating the toxic effect of CdS NPs on the synthetic bacterial cells.