Research On Synthesis And Application Of Phosphorylcholine And Its Copolymer

As an important biodegradable tissue engineering material,polylactic acid is widely used in tissue engineering,however,the blood compatibility of application can't meet clinical requirement,so it is necessary to further improve its blood compatibility.Surface grafting excellent anticoagulant substance is an efficient method to improve the blood compatibility,therefore,arginine-glycine-aspartic acid(RGD),as a bridge,connects 2-methacryloyloxyethyl phosphorylcholine(MPC)and polylactic acid is proposed,and this can not only form the hydrophilic algae-like chain structure,but also enhance the migration ability of MPC group,which is helpful to improve blood compatibility.Bionic is one of the important direction of novel biomaterials,phosphorylcholine(PC)is the basic unit of lecithin membranes hydrophilic end groups,Materials modified with PC group can form a similar structure with cell membrane,which can efficiently prevent protein adsorption and cell adhesion,showing excellent blood compatibility.Methacryloxyethyl phophorylcholine(MPC)was successfully synthesized in this paper,the synthesis condition of 2-chloro-1,3,2-dioxa-phospholane(COP)was optimized:molar ratio between ethylene glycol and phosphorus trichloride was1:1.1,reaction temperature 4-6?,the solvent of CDP oxidation was replaced by low toxicity high boiling toluene,the purification of CDP and 2-chloro-1,3,2-dioxa-phospholane(COP)was combined in order to improve COP and MPC yield.PLGA-(PEG-ASP)n is a novel biodegradable block copolymer,its reactive group can be adjusted through changing the density of side amino.Surface modification is needed to further improve its blood compatibility.PLGA-(PEG-ASP)n grafted with MPC was prepared through Michael addition,FTIR?XPS were used to characterize polymer'structure and analyze surface elements,the results showed successful graft and migration of PC group to surface.Contact angle and water absorption was employed to illustrate hydrophilicity,with increasing content of MPC,water contact angle reduced to 18°,water absorption increased to 44%,the hydrophilicity was enhanced;absorbed water formed hydrated layer on the surface,and its greasy lubrication reduced friction coefficient of the material;material degradation process can be divided into two phases:firstly,the fracture fragments of PEG diffused out of the matrix with a relatively fast degradation rate,secondly,some long-chain PLGA block degraded into small molecular fragments and diffused out of the matrix with decreased degradation rate.arginine-glycine-aspartic acid(RGD)was grafted to PLGA-(ASP-PEG)n through functional condensation reaction to research"bridge" RGD's effects on material properties.existence of hydrophilic amino and amide group of RGD was proved on surface;water contact angle reduced to 22°,water absorption increased to 21%,hydrophilicity of polymer grafted with RGD was enhanced;hydrated layer's greasy lubrication reduced friction coefficient of the material;PLGA-(ASP-PEG)n-RGD degradation process had a similar phase with polymer grafted with PLGA-(ASP-PEG)n-MPC,but the former had a faster rate,because terminal carboxyl groups in RGD had a catalysis on hydrolysis of PLGA segment.To overcome reduced PC group activity caused by directly grafting,prolonging the chain length of surface molecular is considered,KOH as catalyst,the MPC monomer was grafted onto PLGA-(ASP-PEG)n-RGD by Michael addition reaction,the preliminary exploration of the reaction condition was finished,FTIR?XPS were used to characterize polymer' structure and analyze surface elements,the results showed MPC monomer was successfully grafted.The modified material's water contact angle reduced to 10°,water absorption increased to 58.6%,hydrophilicity of polymer was obviously improved;substantially enhanced water absorption indicated material surface formed a thicker hydration layer,this layer further reduce the friction coefficient.