Functional Peptides And Gene Complexes For Promoting Endothelialization Of Material Surface

Tissue-engineered vascular grafts play an important role in the treatment of cardiovascular diseases.However,artificial vascular grafts,especially small-caliber artificial vascular grafts,often encounter the thrombosis,intimal hyperplasia,restenosis and even occlusion in clinical use.This is closely related to the lack of blood compatibility and bioactive endothelial cells(ECs)layer of artificial vascular grafts.Therefore,how to improve the blood compatibility and rapid endothelialization ability of the surface of artificial vascular grafts is the key to the treatment of cardiovascular diseases.In this thesis,according to the problems in the use of small-caliber vascular grafts,surface modification was utilized to prepare a variety of functionalized surfaces based on hydrophilic polymers,ECs-targeting functional peptides and gene complexes.The functionalized surfaces had well blood compatibility and could promote the adhesion,spreading,proliferation and migration of ECs on the surface of vascular grafts.This could enhance the rapid endothelialization ability of vascular grafts and ensure their in vivo performance.1.Poly(?-caprolactone)-b-poly(isobutyl-morpholine-2,5-dione)(PCL-PIBMD)and silk fibroin(SF)were used to prepare PCL-PIBMD/SF nanofibrous scaffolds with different weight ratios of PCL-PIBMD and SF through electrospinning technology.These nanofibrous scaffolds possessed different properties including fiber diameter,hydrophilicity,porosity and mechanical properties.PCL-PIBMD/SF blend scaffolds were optimized to obtain the scaffolds with a weight ratio of 90/10 to have superior mechanical performance and high porosity for further use.In order to maintain the stability and integrity of plasmid complexes loaded in scaffolds,the composite scaffolds were fabricated by alternatively layer-by-layer electrospinning and electrospraying techniques.These composite scaffolds showed obviously low platelet adhesion and good histocompatibility.They could effectively enhance the adhesion,spreading and proliferation of human umbilical vein endothelial cells,thereby promoting the endothelialization of materials surface.2.PCL-PIBMD and SF were firstly used to fabricate a small-caliber vascular graft(diameter,2 mm)by electrospinning technology,and then biofunctionalized with hydrophilic poly(ethylene glycol)(PEG)and two ECs-targeting functional peptides(CREDVW and CAGW)with the purpose of enhancing blood compatibility and endothelialization.The successful grafting of PEG and functional peptides was confirmed by X-ray photoelectron spectroscopy(XPS).The suitable surface wettability of the modified vascular graft was testified by water contact angle analysis.The surface hemocompatibility was verified by platelet adhesion assays and protein adsorption assays,and the results demonstrated that both platelet adhesion and protein adsorption on the biofunctionalized surface were significantly reduced.In vitro cell studies demonstrated that the biofunctionalized surface with suitable hydrophilicity and functional peptides could selectively promote the adhesion,spreading,proliferation and migration of ECs.More importantly,this biofunctionalized small-caliber vascular graft showed high long-term patency and endothelialization after ten weeks of in vivo implantation.3.mPEG-b-PLGA-g-PEI-PEG-Biotin gene vector was firstly synthesized and its pDNA condensing ability was investigated.The gene vector loaded pDNA to form gene complexes nanoparticles(NPs).Cytotoxicity and in vitro transfection experiments showed that the mPEG-b-PLGA-g-PEI-PEG-Biotin gene vector had relatively low cytotoxicity and could efficiently transfect ECs.Then,with the help of the biotin-avidin system,the protease-responsive gene delivery surface was constructed by anchoring NPs to Au surface modified with protease-cleavable peptides.The protease-responsive gene delivery surface could responsively release gene complexes.The results of biological experiments showed that protease-responsive gene delivery surface could effectively transfect ECs,improve the expression level of specific proteins and corresponding m RNA in ECs,and thereby promote the proliferation and migration of ECs on the materials surface.In summary,surface modification based on hydrophilic PEG,functional peptides and gene complexes could improve the blood compatibility and rapid endothelialization ability of the surface of artificial vascular grafts.Hydrophilic PEG could improve the surface wettability of the materials surface.The ECs-targeting functional peptides could specifically adhere endothelial cells.Gene complexes could effectively transfect ECs and promote the rapid proliferation of ECs,thus inducing endothelialization.We provided a new method for the combination of gene therapy and tissue-engineered vascular grafts,and also provided a new strategy for the biofunctionalization of smallcaliber artificial vascular grafts.This is of great significance for the treatment of cardiovascular diseases.