Construction And Research Of High-Efficiency Nano-Antibacterial System Based On Nearinfrared Light Response

In recent years,bacterial infection has caused serious impact on human production and life.If not brought under control,it could lead to 10 million deaths and more than$100 trillion in damage by 2050.At present,the traditional treatment is the use of antibiotics,although countless lives have been saved,but the misuse of antibiotics,especially the misuse of antibiotics,can lead to the emergence of drug-resistant strains.However,according to the current situation,the time needed to develop new antibiotics is far behind the rate of bacterial resistance,so there is an urgent need to develop new antibacterial strategies.At present,photo-responsive antimicrobial therapy has received extensive attention.For example:antibacterial photodynamic therapy,antibacterial photothermal therapy,antibacterial photoinduced gas therapy and other treatment methods.This thesis is to study one of the promising photothermal therapy for sterilization treatment means.Photothermal therapy is a treatment method that converts enough light energy into heat energy for antibacterial use.Photothermal therapy,especially near-infrared light（NIR）,has attracted extensive attention due to its advantages,such as easy access to light source,strong tissue penetration,and rapid sterilization（it can be sterilized in a few minutes）.The research work of this paper mainly includes the following contents:1.Biodegradable and near-infrared activated photothermal nanoconverters for bacterial inactivation.The development of biodegradable nanomaterials for near infrared photothermal antibacterial strategy is of great significance to improve the biosafety of nano-antibacterial strategy in clinical application.In this study,we developed a novel nano-antibacterial strategy in which a biodegradable charge-transfer nanocomplex（CTN）acts as a photothermal nanoconverter that can be activated by highly efficient near-infrared light.CTN was synthesized by self-assembly induced by oxidation of 3,3’,5,5’-tetramethylbenzidine（TMB）molecules.The nanocomposite can efficiently convert light energy to heat energy at around 900 nm,with a photothermal conversion efficiency of up to 30%.More importantly,the nanocomposites can spontaneously degrade within 12 h under physiological conditions.Gram-positive B.subtilis and Gram-negative E.coli can be inactivated within 2 min by using the photothermal effect of the nanocomposite.In addition,the mechanism of its inactivation was systematically discussed through the live/dead staining of bacteria and the change of bacterial morphology.The results showed that the damage of bacterial cell membrane caused by photothermal effect was the cause of its antibacterial action.2.Preparation of amino-encapsulated polystyrene（NH₂-PS）coated indocyanine green（ICG）nanocomposites and their photothermal and antibacterial properties.NH₂-PS was synthesized from polystyrene by fine emulsion polymerization between styrene and glycidyl methacrylate and then by adding ethylenediamine.When the concentration of ICG reached 0.1 mg·m L^-1,the adsorption capacity and adsorption rate reached 10μg and 97%.NH₂-PS-ICG nanocomposite material can convert light energy of about 808 nm into heat energy,and the photothermal efficiency reached 13%.Therefore,B.subtilis and E.coli can be destroyed in 4 min by using the photothermal properties of the nanocomposite material.In addition,we further discussed the antibacterial mechanism of the nanocomposites through the live/dead staining of bacteria and the change of bacterial morphology,and the results showed that the photothermal effect of bacterial cell membrane damage is the cause of its antibacterial effect.In conclusion,we have successfully developed an efficient nano-antibacterial strategy with good biocompatibility and excellent bactericidal ability,which provides a way for the development of new antibacterial materials and has a wide application prospect in biomedical materials.