Construction And Biocompatibility Study Of Phospholipid/Specific Peptides Biomimetic Multifunctional Coating

Late thrombosis formation and stent restenosis are the main complications in the clinical application of cardiovascular stents. It has been a hot topic of the surface modification of cardiovascular implants materials to obtain the concept of anti-coagulation and endothelial. Currently, there are many kinds of functional molecules on the surface modification of cardiovascular stent materials. The different functional biological molecules are selected to construct the bionic surface for the different functions design. In this study,non-specific resistion role imitation cell membrane structure of 2-methacryloxyethyl phosphorylcholine (MPC) and endothelial progenitor cells (EPCs) - specific recognition and capture of the polypeptide (TPSLEQRTVYAK-GGGC-K, PT) as the target molecules. The construction of single and polylysine (PLL), fibronectin (Fn) mediated compound with anti-coagulation, anti-proliferative and rapid-endothelialization phospholipid / PT functional composite coating on the surface of the titanium (Ti) substrate. The physical and chemical properties, blood compatibility evaluation, cytocompatibility evaluation and animal in vivo evaluation of the surface coating were carried out.The PMMPC polymer was synthesized by free radical copolymerization between 2-methacryloxyethyl phosphorylcholine (MPC) and methyl acrylate (MA). The PMMPC grafted dopamine (DA) was named after PMMDA by condensation reaction.The PMMDA grafted PT was named after PMMDP by condensation reaction. The novel polymer of PMMDP imitated membrane structure contains phosphorylcholine (PC)groups, EPC-specific peptides and catechol groups. The PMMDA and PMMDP were oxidized to POMMDA and POMMDP under alkaline conditions. The PMMDP, PMMDA,PMMPC, POMMDA and POMMDP were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectrum (1HNMR), gel permeation chromatography (GPC) and ultraviolet spectrum (UV) to demonstrate the series of polymers synthesised successfully.Via the chelating effect between catechol group in PMMDP polymer and titanium (Ti)substrate, the multifunctional coating of Ti@PMMDP was constructed successfully on the titanium surface. The Ti@PMMDP coating was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), water contact angle measurements and atomic force microscopy (AFM), respectively. The amount of PMMDP coating on the Ti surface was quantified by using the quartz crystal microbalance with dissipation (QCM-D).The samples were immersed in PBS solution with thermostatic shaker concussion(37? 60 rpm) for 22 days to test the stability of the coating. The immersed surface morphology of the PMMDP coating was observed by scanning electron microscopy(SEM), XPS, and the soaking solution was analyzed by UV spectroscopy. The results show that the coating has good stability. The blood compatibility experiments showed that the coating can effectively inhibit platelet adhesion and activation, fibrinogen adhesion and degeneration. The results of cell compatibility testing proved that the Ti@PMMDP coating could inhibit the proliferation of SMCs and promotion EPCs cell adhesion, homing and proliferation. Furthermore, there was no obvious inhibitory effect to ECs cells.The polylysine (PLL) and fibronectin (Fn) were selected to mediated compound multilayer phospholipid /PT coating for improving the expression amount of phospholipid and PT. The PMMDA was immobilized to Ti surface via the chelating effect. Subsequently,the PLL/Fn, POMMDA/POMMDP and PT were assembled to the last layer in turn via condensation reaction, electrostatic interaction and hydrogen bonding interaction between the carboxyl and the amine groups, Schiff base reaction and Michael addition reaction between the amine groups of PT and the quinone groups on POMMDA/POMMDP. The material characterization of the coating surface was carried out by FTIR, XPS and other methods. The biological evaluation and mechanism study of the coating demonstrated that phospholipid groups contribute to anti-coagulation and inhibition the proliferation of SMCs,but have no effect to ECs; the PT could promote the adhesion, homing and proliferation of EPCs, and the PT content was positively correlated with the promotion of the proliferation ability. The relatively better blood and cell compatibility was belonged to Ti@PCDLOPTPT sample through comprehensive biological evaluation. Furthermore, the Ti@PCDLOPTPT samples were implanted into dog femoral arteries for 15 days and 30 days. In vivo experiments results revealed that the Ti@PCDLOPTPT samples contribute to anti-thrombus and inhibition of intimal hyperplasia, and capturing EPCs in blood circulation to speed up the rate of endothelialization.In summary, focusing on the specific requirements of cardiovascular implants for anticoagulation and promoting endothelial, the MPC and PT were chosen to construct the multifunctional surface in this research. The work demonstrated that construction of anti-coagulant and promoting endothelialization multifunctional surface in cardiovascular implantation materials is feasible. These understandings may provide valuable theoretical guidance for the follow-up study of cardiovascular implants.