Preparation Of QPDMAEMA-b-PEGMA-b-PDFHMA Copolymer And Its Antibacterial Properties

On the surface of biological materials,bacterial adhesion and subsequent biofilm formation is a common problem.Although people have made great efforts in the design and construction of the surface of antibacterial coating,a large number of bacterial infection occur with indwelling medicals devices have also emerged,which greatly increases the financial burden of patients'families.Nearly half of the infections caused by bacteria are related to the biofilms formed on various surfaces,so it is still a difficult task to constructed surfaces with anti-adhesion and antibacterial properties.In recent years,polymer-based antibacterial materials have received extensive attention,but there are still many problems that need to be considered and solved,such as the accumulation of dead bacteria on the coating surface,the formation of biofilms,the design and preparation of multifunctional antibacterial coating structures and so on.Therefore,it is important to avoid early bacterial adhesion and prevent the formation of biofilms.The selection of appropriate anti-adhesion units and bactericidal units,as well as the distribution of each unit on the surface of the polymer coating are all of the concerns of this article to solve the main problems.In this work,the fluoropolymer with low surface energy and poly(poly(ethylene glycol)methyl ether methacrylate)(PEGMA)with electrostatic repulsion and interfacial hydration was chosen as a common antiadhesion block and quaternary ammonium salt with bactericide properties as a sterilization block.The triblock copolymers of poly(2-(dimethylamino)ethyl methacrylate)-b-poly(poly(oligo ethylene glycol)methyl ether methacrylate)-b-poly-(dodecaflfluoroheptyl methacrylate)(PDMAEMA-b-PEGMA-b-PDFHMA)were synthesized by the reversible addition-fragmentation chain transfer(RAFT)polymerization method.Then,the synthesized triblock copolymers were quaternized to obtain the antibacterial materials(QPDMAEMA-b-PEGMA-b-PDFHMA).theQPDMAEMA-b-PEGMA-b-PDFHMA antibacterial coating was prepared by dropping the QPDMAEMA-b-PEGMA-b-PDFHMA solution on the wafer surfaces and dry at room temperature.The specific content is as follows:1.ABC triblock copolymer QPDMAEMA-b-PEGMA-b-PDFHMA copolymer preparation,coating construction and anti-adhesion and bactericidal properties(1)The DDMAT-PDMAEMA macromolecular chain transfer agent was synthesized by S-dodecyl-S'-bis(?,?"-methyl-?"-acetic acid)trithiocarbonate(DDMAT)as RAFT reagent,methyl 2-(dimethylamino)ethyl acrylate(DMAEMA)as monomer,tetrahydrofuran(THF)as organic solvent and azobisisobutyronitrile(AIBN)as initiator.Then,using DDMAT-PDMAEMA macromolecular chain transfer agent,a diblock copolymer PDMAEMA-b-PEGMA was prepared by poly(ethylene glycol)methyl methacrylate as monomer.Further ABC triblock copolymer(PDMAEMA-b-PEGMA-b-PDFHMA)was synthesized by fluorine-containing monomer of dodecafluoroheptyl methacrylate(DFHMA).The synthesized triblock copolymer was quaternized with 1-bromooctane to obtain QPDMAEMA-b-PEGMA-b-PDFHMA polymer with antibacterial performance.A similar method was used to synthesize two quaternized diblock copolymers QPDMAEMA-b-PEGMA and QPDMAEMA-b-PDFHMA for comparison.(2)The copolymer coating was constructed by drip coating.The coating stability test results show that the copolymer coating immersed in a high ionic strength PBS solution for 7days under dynamic conditions also can maintain high integrity.S.aureus and E.coli were used as gram-positive and gram-negative bacteria models,and the agar plate colony counting method was used to count the number of bacteria on the coating surface and scanning electron microscope(SEM)was choosed to observe its morphology.Experimental results show that the copolymer coating has excellent anti-adhesion and antibacterial properties against both S.aureus and E.coli.this maybe due to the bactericidal ability of the quaternary ammonium salt and the antifouling properties of the synergy between the low surface energy of fluoropolymer and hydrophlic shell of PEGMA.It was found that the synergistic effect of fluoropolymer and PEGMA can enhance the antifouling performance of the coating.(3)The shape and number of platelets and red blood cells(RBC)are used to evaluate the anti-adhesion performance of the coating samples.Compared with the original silicon wafer,the number of platelets attached to the QPDMAEMA-b-PEGMA-b-PDFHMA coating is greatly reduced,and the platelets attached to the sample surface remain round.Similar results to platelet behavior were also observed in the RBC analysis.These results confirm that QPDMAEMA-b-PEGMA-b-PDFHMA coating has excellent anti-cell adhesion effect,and the QPDMAEMA-b-PEGMA-b-PDFHMA antibacterial coating has potential application prospects in medical devices.2.The influence of the degree of polymerization of the quaternary ammonium salt segment in the ABC triblock copolymer on the anti-adhesion and bactericidal properties(1)The fluorine-containing monomer,polyethylene glycol methyl methacrylate(PEGMA)and quaternary ammonium salt are selected to synthesize PDMAEMA_n-b-PEGMA-b-PDFHMA copolymers(n was 4,8,16,25,41 respectively)with different PDMAEMA lengths by RAFT polymerization method.Then the synthesized triblock copolymer was quaternized to obtain the QPDMAEMA_n-b-PEGMA-b-PDFHMA antibacterial copolymer.the IR,NMR and XPS results show that 5 kinds of quaternary ammonium triblock copolymer QPDMAEMA_n-b-PEGMA-b-PDFHMA was successful prepared.(2)The results of the anti-stick agar plating experiment and the SEM image show that the coating surface of quaternary ammonium salt polymerization degree of 25 and 41 has a small amount of bacterial adhesion.when the quaternary ammonium salt polymerization degree is below 16,there is almost no bacterial adhesion on the surface of the plate.The possible reason is that when the quaternary ammonium salt polymerization degree is above 25,the distribution ratio of the quaternary ammonium salt segment on the coating surface is much larger than that of the fluorine-containing segment and the PEG segment,which affects the anti-adhesion performance of the sample coating.From the bactericidal agar plates image and SEM image,it can be obtained that there is some bacterial adhesion on the surface of quaternary ammonium salt polymerization coating with the degree of 4 and 8.However,there is almost no bacterial adhesion on the surfaces of quaternary ammonium salt polymerization coating with degree above 16.The possible reason is that when the degree is below 16,on the coating surface the distribution ratio of the fluorine-containing segment and the PEG segment is much larger than that of the quaternary ammonium salt segment,which affects the bactericidal performance of the sample coating.