Synthesis Of Polypyrrole-based Photothermal Agents For Photothermal Antibacterial Applications

Due to the overuse and misuse of antibiotics as well as the poor drug management,the emergence of antimicrobial resistance（AMR）and multi-drug resistant（MDR）bacteria is a great threat to human health.Therefore,it is urgent to develop simple and cost-effective antimicrobial therapy strategies to address bacterial infections.Antimicrobial photothermal therapy（a PTT）has attracted significant attention because of its strong therapeutic effect,deap tissue penetration and abundance of photothermal agents.An ideal photothermal agent should exhibit high photothermal conversion efficiency（PCE）and excellent biocompatibility.Polypyrrole（PPy）,one of the CPs,has some intriguing benefits,including easy way of preparation,low-cost,high PCE and good biocompatibility.However,the native PPy-based materials have poor water dispersibility,which may limit their pratical applications in biomedicines.Thus,dispersing/stabilizing agents have to be introduced during the oxidative polyermization or surface post-functionalization to improve the water dispersibility of PPy-based nanostructures.Herein,the photothermal antibacterial efficiencies of PPy nanoparticles（NPs）towards the planktonic and surface adhered bacteria were investifated.The PPy NPs were stabilized with polyethylenimine（PEI）and poly（vinyl alcohol）（PVA）.The PEI-stabilized PPy NPs（PPy-PEI NPs）were prepared to eradiate the planktonic bacteria in solution,while the PVA-stabilized PPy NPs（PVA-PPy NPs）was prepared and co-deposited with tannic acid（TA）onto the biomedical implants to prevent the bacterial adhesion and biofilm formation.1.The PPy-PEI NPs with different pyrrole contents were prepared by a simple chemical reaction.The characteristics of the PPy-PEI NPs were analyzed by dynamic light scattering（DLS）,scanning electron microscope（SEM）,transmission electron microscope（TEM）,and UV-Visible absorption spectroscopic analyses.Moreover,the antibacterial photothermal activity of the PPy-PEI NPs was evaluated against Escherichia coli（E.coli）,Pseudomonas aeruginosa（P.aeruginosa）,Staphylococcus aureus（S.aureus）and Methicillin-resistant S.aureus（MRSA）.Our results unveil that the synthesized PPy-PEI NPs could completely inhibit the growth of bacterial pathogens under 808 nm NIR irradiation.Therefore,PPy-PEI NPs,as photothermal agents,have an excellent application prospect in the field of antimicrobial photothermal therapy.2.The PVA-PPy NPs were prepared by oxidative polymerization using FeCl₃ as the oxidant.Subsequent mixing of the PVA-PPy NPs solution mixture with TA was facilitated by hydrogen bonding.The as-formed TA/PVA-PPy NPs can be deposited with good adhesion onto solid materials in a substrate-independent manner.The hydrophilic TA/PVA-PPy NPs-deposited titanium（Ti-TPP）surface can reduce the adhesion of S.aureus and E.coli.In addition,the Ti-TPP surface had photothermal property under 808 nm NIR irradiation,which can kill the adhered bacteria via the hyperthermal effect.Upon exposure to NIR,the respective survival rates of S.aureus and E.coli on the Ti-TPP surfaces were only 1.7%and 2.8%,in comparison to those on the pristine Ti surfaces.Furthermore,the Ti-TPP surface could prevent the formation of early-stage biofilm under NIR irradiation.The TA/PVA-PPy NPs composites can be utilized as a contact-photoactive antibacterial coating for biomedical applications.To sum up,in order to solve the MDR problem,this paper synthesized the water-dispersed PPy photothermal agent and constructed the PPy photothermal coating through simple polymerization reaction.PPy show the excellent performance of field makes it to gram-positive bacteria and gram-negative bacteria have good antibacterial effect of field,and has good biocompatibility and excellent resistance to bacterial biofilm effect,the selection of field of antimicrobial therapy of field and the development of medical material surface functionalization coating has certain academic significance and application prospects.