Identification And Inactivation Of Pathogens By Vancomycin And Protoporphyrin-Containing Polymeric Materials

Bacterial infections cause serious health problems and endanger human life.In particular,infections caused by Gram-positive bacteria can cause a variety of serious diseases,including sepsis,bacteremia,pneumonia,osteomyelitis and endocarditis.Since the application of penicillin in 1942,nearly twenty kinds of antibacterial drugs have been used in clinical practice,and have played an active role in the treatment of infections and the control of the spread of bacterial infectious diseases.They have made great contributions to the development of medical care and human health.However,the emergence of multidrug-resistant bacteria?MDR? due to the irrational use of antibiotics in clinic has increased the mortality rate of bacterial infections.In addition,quick and accurate identification of pathogens can not only improve the success rate of treating patients with severe bacterial infections,but also avoid the abuse of antibiotics leading to the occurrence of bacterial resistance.Fluorescence detection technology shows great potential in bacterial identification due to its high sensitivity and high speed.Fluorescent polymeric antimicrobials can identify bacteria by fluorescence technology and successfully inactivate them.Therefore,the design and synthesis of fluorescent polymeric antimicrobials can provide an integrated bacterial diagnosis and inactivation platform for the increasingly serious bacterial infection problems.Based on the above research objectives,two fluorescent polymeric antimicrobials were synthesized in this thesis.Firstly,water-soluble polythiophene is an important fluorescent conjugated polymer.Vancomycin can combine with D-Ala-D-Ala unit on the cell wall of Gram-positive bacteria to achieve targeted effect.In this work,an active polythiophene derivative containing reactive pentafluorophenyl?PFP? ester pendant groups was prepared via Fe³⁺-catalyzed oxidative polymerization.As far as we know,this is the first report of active polythiophene with reactive PFP ester moieties.The active polythiophene derivative was conjugated with vancomycin and ?-methoxy-?-amino poly?ethylene glycol??mPEG-NH₂? via reactive ester-amine reaction,resulting in the formation of water-soluble and fluorescent vancomycin-containing polythiophene?PTPVan?.Since vancomycin can selectively interact with Gram-positive bacteria and kill them,the antibacterial properties of PTPVan were evaluated.The detection of Gram-positive bacteria was carried out by observing the color change and fluorescence response of bacteria upon incubation with PTPVan through naked eye and fluorescence spectroscopy,respectively.The staining of Gram-positive bacteria was observed using confocal laser scanning microscopy?CLSM?.Secondly,protoporphyrin?PPIX? is a common photosensitizer?PS?,which can emit red fluorescence and produce reactive oxygen species?ROS? under visible or near infrared irradiation for photodynamic antimicrobial chemotherapy?PACT?.Polyethyleneimine?PEI? is a water-soluble polymer with positive charge,which can enhance the interaction between photosensitizer and bacteria.In this work,a simple hydrothermalapproachwasemployedtopreparetheprotoporphyrin IX-polyethylenimine nanoparticles?PPIX-PEI NPs? containing abundant amine groups and PPIX moieties.The as-obtained PPIX-PEI NPs exhibit antibacterial properties against both Gram-positive and Gram-negative bacteria.The presence of PPIX in the PPIX-PEI NPs can generate reactive oxygen species?ROS? under 635 nm laser irradiation,which enhance the antibacterial properties of the PPIX-PEI NPs against Gram-positive bacteria.Thus,the PPIX-PEI NPs display a synergistic antibacterial activity against Gram-positive bacteria in the combination of antibacterial photodynamic therapy?PDT?.In addition,emission of red fluorescence by the PPIX-PEI NPs can help to differentiate bacteria and observe the bacterial morphologies using a CLSM..