Antibacterial Modification Of Zwitterionic Polymers To Polyvinyl Alcohol Membranes

Biomedical materials(Biomaterials)are materials which are used in the diagnosis,treatment,repair or replacement of biological tissues or organs of biological systems to enhance or restore their functions.When the biomaterial was implanted into the human body,it initially interacted with nonspecific protein or cells,which would contaminate the surface of the materials and then affect the application of the materials.In order to solve this problem,scholars have proposed the concept of"anti-fouling",which is to modify the surface of some biomedical materials to make it have a certain anti-fouling ability and enhance the application of materials.Polyvinyl alcohol(PVA)is a medical polymer which has good biocompatibility,excellent physical properties and low toxicity.It is widely used in the biomedicine applications.In the early studies,we found that when PVA hydrogels were transplanted into animals'eyes as artificial cornea,cell adhesion and proliferation on the PVA surface could be observed in the later period.That would cause the failure of transplant surgery.In this thesis,PVA film was modified with zwitterionic polymer to improve the anti-fouling ability of materials.In this paper,we firstly synthesized carboxyl zwitterionic monomers by a novel method and modified PVA membranes surface with zwitterionic polymers by using two grafting methods,graft from and graft to respectively.The surface constitution,physical properties and biological properties of modified PVA film were studied.The main results are described as follows:1.In a solvent-free system,the tertiary amines DMAEMA and DMAPAA were quaternized with acrylic acid to prepare two carboxylic zwitterions,namely the methacryl-type CBMA and the methacrylamide-type CBAA.The structures of CBMA and CBAA were characterized by IR and ~1HNMR.Taking the quaternization of DMAEMA and acrylic acid as an example,the optimal reaction conditions were as follows:the reaction molar ratio(nDMAEMA:nAA)is 1:2,the stirring speed was 200 r/min,the reaction time was 24 h and the reaction temperature was 25?,the yield of the reaction product reached 75%.2.With PVA film as the substrate,using the method of"graft from"polymerization to modify its surface.The acylation reaction between hydroxyl groups on the surface of the PVA film and Br groups of BIBB took place initially.Then two kinds of zwitterions(SBMA and CBMA)were grafted on the surface of membrane by surface-initiated atom transfer radical polymerization(SI-ATRP).The surface of the membranes would be rough after grafted.Its hydrophilicity increased dramatically,the minimum water contact angle decreased from 39.6°to 7.2°.The modified PVA still had good capacity of water storage and the water content was more than 62.09%.The membrane volume increased with the increase of zwitterions concentration,the volume ratio remained between 150%-250%.The visible light transmittance was above 88%.Mechanical properties and thermal properties decreased slightly after grafted,the tensile strength and tensile strain at break were in 1.23-1.85 MPa and 361.7-471.1%,respectively.After grafted zwitterions,the anti-protein adsorption capacity of PVA membrane was significantly increased and the lowest adsorption amount was up to2.25?g/cm~2.The cytotoxicity grade of zwitterions modified PVA membrane was in 0-1 scope,which indicated this film had no cytotoxicity.In addition,the membrane surface had good resistance to cell adhesion after grafted zwitterions.3.Zwitterionic copolymer was synthesized via free radical copolymerization with glycidyl methacrylate(GMA)and the zwitterions.The PVA membrane was modified by the copolymer through graft to method.After the surface was grafted zwitterionic copolymer,the membrane surface became rougher.The overall composition was greatly increased in hydrophilicity.The minimum water contact angle decreased from 39.6°to 8.5°.The water content was above 70.79%,and the water storage capacity was good.At the same time,the membrane volume increased slowly with the increase of the copolymer concentration,it remained between 102%-121%.After grafted zwitterionic copolymer,the optical properties of PVA film slightly decreased and the visible light transmittance decreased to 60.3%with the high modified concentration.The tensile strength and tensile strain at break were in the range of 2.38~2.63 MPa and 552.3-655.6%respectively.Thus,the modified PVA membranes maintained good mechanical properties.The grafted zwitterionic copolymer obviously enhanced anti-protein adsorption capacity of PVA membrane and the lowest amount of adsorption was 4.42?g/cm~2.Cytotoxicity grade was 0.The result showed that the modified membrane had no cytotoxivity.The surface modified by zwitterionic copolymer also showed good resistance to cell adhesion.