Photoactive Nanomaterials For Anti-infective Treatment

Bacterial infections have been one of the killers threatening human life.The development of nanotechnology and the application of phototherapy provide new ideas for solving this problem.Except for using as antibacterial agents themselves,some of nanomaterials could be also used as delivery tools for antibacterial drugs.Light-activated therapies,especially photothermal and photodynamic therapy,have the advantages of noninvasive nature and remote controllability.Therefore,nanomaterials based on photothermal/photodynamic therapy show great potential in antibacterial applications.However,most of the current photothermal antibacterial nanomaterials have limited photothermal conversion efficiency.Single photothermal therapy may lead to incomplete elimination of bacterial infection.The increasing dosage of photothermal nanoagents will increase cytotoxicity.Although photodynamic therapy is a safer method to combat bacterial infection,cationic photodynamic nanoparticles usually chosen to enhance photodynamic antimicrobial activity are beneficial to cellular internalization,which will increase cell cytotoxicity.Based on these problems,we conducted the following researches:In the first part of this work,we prepared silica-coated gold-silver nanocages(Au-Ag@SiO2 NCs).The composite nanoparticles possessed excellent photothermal property and sustained release of Ag ions and thus achieved combined anti-infective therapy.Experimental results showed that Au-Ag@SiO2NCs could cause severe damage to bacterial membranes through photothermal effect and Ag ions,which led to the death of bacteria.Besides,Au-Ag@SiO2 NCs exhibited good killing ability against S.aureus biofilm when exposed to NIR irradiation.More importantly,the remarkable bactericidal activity was successfully proved vivo with a wound infection model.In the second part of this work,Rose Bengal(RB)-polydopamine(PDA)nanoparticles were decorated in a layer-by-layer fashion with polymyxin B(PMB)and gluconic acid(GA)to generate pH-responsive photodynamic nanoparticles(RB@PMB@GA NPs).RB@PMB@GA NPs remained negative at physiological pH and exhibited good biocompatibility.When RB@PMB@GA NPs were exposed at an acidic infectious environment,the charge of RB@PMB@GA NPs became positive;thus RB@PMB@GA NPs stuck to the bacterial surface via electrostatic interactions and enhanced the bacterial photoinactivation efficiency.The experiment results in vivo and in vitro proved that RB@PMB@GA NPs possessed low cytotoxicity,effective antimicrobial activity,and excellent biofilm penetration and elimination abilities.The above two photoactive nanomaterials achieved highly efficiency and broad-spectrum antibacterial properties,and possessed excellent elimination effect on biofilms.They also effectively removed bacteria and biofilm infections in vivo.Additionally,compared with single light treatment,they also reduced toxicity.The researches provide new strategies for the design of nanomaterials with efficient anti-infective effect and good biological safety.