Synthesis Of Cationic Polypeptides With UCST,Study On Oxidation Response And Antibacterial Properties

Stimulus-responsive polymers have important theoretical research value and application prospects in the fields of drug delivery,tissue engineering,and biosensing.Due to the excessive use of antibiotics and the emergence of resistant bacteria worldwide,these"super"bacteria are threatening people’s health and life.Research work on antimicrobial materials has once again become a research hotspot.The combination of stimuli responsiveness and antibacterial properties to build intelligent antimicrobial materials can avoid the emission of bioactive materials in the environment,thereby reducing the risk of drug-resistant bacteria,and in addition to reducing the toxicity to normal cells.However,the research work of such intelligent antibacterial materials is still in its infancy,and people’s understanding of the relationship between the structure and properties of such materials is still unclear.This paper focuses on the effects of polymer side group structure and topology on polymer responsiveness and antibacterial properties.We synthesized L-glutamic acid esters of BLG-S-Cl NCA by a series of reactions.The desired BLG-S-Cl NCA is then formed by triphosgene cyclization.Then,through ring-opening polymerization,azidation,click chemistry and quaternary ammonium salting reaction,the ion exchange reaction produces polypeptides of three different counterions and LCST-type polypeptides with OEG7 in the side chain.It was also found that PBLG-S-ImI,PBLG-S-ImBF₄ and PBLG-S-OEG₇ have oxidation and temperature double response properties.We found that the T_CPP of PBLG-S-ImI and PBLG-S-ImBF4 gradually increased with the increase of polymer concentration,while the TCP of PBLG-S-OEG7 changed little with the increase of polymer concentration.After oxidation,the T_CP of PBLG-S-ImI gradually increases with the increase of the concentration of H₂O₂,and PBLG-S-ImBF₄ is the opposite.The T_CP of PBLG-S-OEG₇ has increased by about 30℃.This may be due to the oxidation of I^-to IO₃^-and BF₄^-to the formation of a more hydrophilic S=O bond and the hydrolysis of fluoroborate.PBLG-S-OEG₇ is due to the formation of a very hydrophilic O=S=O and S=O bond.Through the test of antimicrobial properties,we get the following information:the MIC value of PBLG-S-ImI and PBLG-S-ImBF₄ is about 0.5-0.6mg?mL^-1,and the hemolysis of PBLG-S-ImI is better than PBLG-S-ImBF,but their hemolysis increase gradually with the increase of polymer concentration.The antibacterial properties of the two counterions do not change at room temperature and body temperature,remain antibacterial,and do not lose the antibacterial effect due to the addition of H₂O_2.Subsequently,we synthesized the triblock polypeptide by introducing long hydrophobic chain polyetheramine 2000 as an initiator,and ion exchange to generate three counterions,and two kinds of triblock polypeptide ionic liquids with different polymerization degrees.The structure was characterized by ¹H NMR,FTIR,GPC,and CD.The temperature response properties were tested by UV-vis.The MIC value was initially explored,and a polypeptide ionic liquid with a smaller MIC value was obtained.Antibacterial,hemolytic and antibacterial mechanisms were also studied.We further explored the relationship between the structure and properties of polypeptides,and gained a deeper understanding of the research of antimicrobial polypeptides.