Study On The Performance And Mechanism Of Inactivation Of Staphylococcus Aurues Under Light Induction

Staphylococcus aureus(S.aureus)is a common environmentally harmful pathogenic microorganism that cause gastroenteritis,pneumonia,body surface infections,endocarditis and myelitis,which poses a serious threat to public health security.In recent years,due to the abuse of antibiotics,the problem of S.aureus drug resistance has become increasingly serious.Hence,the development of new inactivation technology is imminent.Photo-inductive bacterial inactivation is the safe and effective bacterial inactivation technique utilizing the photodynamic effects produced by different bands of light to achieve the purpose of bacterial inactivation.Based on this,this paper developed a visible-light-driven photocatalytic material denoted as Carbon dots/Graphic carbon nitride(CDs/CN).Meanwhile,the cooperative enhancement mechanism of infrared-visible light inactivation was reported for the first time.The main contents and results of this paper are as follows:(1)Construction of metal-free photocatalyst and investigation of its performance and inactivation mechanism of S.aureus.CN was synthesized by using urea as precursor,and CDs were doped on CN by the way of impregnation to obtain metal-free photocatalyst CDs/CN.Compared with pure CN,CDs/CN has significantly enhanced visible light absorption capacity.Meanwhile,it also exhibited a narrow band gap and excellent photoelectric properties.Under visible light,CDs/CN had a higher lethality rate for S.aureus than the CN treatment group.In 100 minutes,the CDs/CN treatment group could reach 96% inactivation efficiency while the CN treatment group was only 64%.Further studies had found that CDs/CN could significantly increase the intracellular reactive oxygen species level of S.aureus under the visible light and destroy its cell membrane structure,promote cytoplasmic leakage,and ultimately lead to bacterial death.(2)The inactivation performance and mechanism of S.aureus under visible-infrared light synergy.Compared with the visible light alone,S.aureus had more excellent inactivation efficiency under visible-infrared light synergy.When the induction time was 6 h,nearly 100% of S.aureus was killed under visible-infrared light synergy,while only 75% lethality was achieved under visible light.Under visible-infrared light,the intracellular reactive oxygen species level of S.aureus increased.The antioxidant enzyme activity was significantly inhibited,thus decreasing the antioxidant capacity.Further studies had found that the induction of infrared light could significantly destroy the S.aureus cell membrane,increase the permeability of the cell membrane,and promote the leakage of intracellular DNA and protein.In addition,infrared light could also enhance the expression of S.aureus autolysin and promote the degradation of peptidoglycan of cell wall,which ultimately led to the death of S.aureus under visible-infrared synergy.The metal-free photocatalyst CDs/CN designed in this paper provides application directions for photocatalytic technology in water disinfection,air purification,medical care and health,etc.At the same time,the inactivation mechanism of S.aureus under visible-infrared light synergy is also helpful to understand the bacterial induction effects of different light sources.