Study On The Fabrication Of Bioactive Molecule-modified Electrospun Materials For Enhanced Endothelialization

Endothelialization of materials is an efficient strategy to achieve the blood compatibility of cardiovascular implants.However,most available implanted materials suffer from lack of biological cues and carnot achieve effective endothelialization in vivo,leading to frequent occurrence of severe complications such as thrombosis and neointimal hyperplasia.Therefore,biofunctional modification of materials is of vital significance to promote the adhesion,proliferation,migration and function of ECs.Since growth factor-induced signaling pathways directly modulate a series of behaviors of ECs,they are widely used to modify materials.The extreme instability of growth factors in vivo has largely impeded their applications yet.To overcome the limitations,several promising modification strategies have been developed so far.For example,gene-modified materials can achieve over-expression and secretion of growth factors from transfected cells through functional gene delivery,thus enhancing endothelialization continually.Glycosaminoglycan-modified materials can stabilize growth factors and facilitate them to bind with their receptors,amplifying the activity of growth factors.Despite the promise of these two strategies,there are still some limitations:low transfection efficiency of ECs cannot achieve desired functions;the structural heterogeneity,immunogenicity,and short half-life of available“natural,GAGs have hindered their applications.Therefore,this study aims to promote the endothelialization of materials rapidly and effectively through addressing these bottleneck problems.(1)Photothermal substrate-mediated functional gene delivery for enhanced endothelialization of electrospun mats.In order to promote gene delivery efficiency of hard-to-transfeet ECs on materials,photothermal materials were fabricated.Porous fibrous PCL mats were prepared by electrospinning.PCL mats coated with PDA were fabricated with the self-polymerization of dopamine.The obtained PCL-PDA mats possess excellent photothermal effect and hydrophilicity.The complex of functional plasmid DNA(pEGFP-bFGF)and PEI was loaded on the surface of PCL-PDA materials.With the irradiation of near infrared laser,ECs were effectively transfected(95%transfection efficiency).The optimal irradiation condition that ensure best transfection and does no harm to cells was achieved.qRT-PCR further demonstrated the mRNA expression of bFGF by transfected ECs.With the photothermal surface-mediated transfection of ECs,the proliferation and migration were significantly enhanced.(2)Sustained release of GAG-mimicking polymers for enhanced endothelialization of electrospun mats.Synthetic GAG-mimicking polymers were used as an alternative of available "natural" GAGs to modify materials.A novel "unit-recombination" strategy was utilized.Two key structural units,sulfonate and saccharide,from the building blocks of GAG,were "recombined" to give GAG analogues by the copolymerization of two monomers.The composition and molecular weight of the copolymers were adjusted to obtain maximum EC proliferation.The GAG-mimicking polymer(pSG)with sulfonate and saccharide units in a ratio of approximately 1.0 and a molecular weight of 9.8 kDa was found to be optimal.The data emphasized the key role of saccharide units in GAG bioactivity and indicated the importance of tuning the copolymer structure to optimize biofunction.The optimized glycopolymer was incorporated into fibrous polycaprolactone(PCL)materials by coaxial electrospinning.These materials showed controlled release of the GAG-mimicking polymers over prolonged periods.The proliferation,migration and function of EC on the glycopolymer-modified PCL fiber mats were greatly improved compared to those on unmodified PCL mats.A likely mechanism underlying these improvements is that the glycopolymers significantly enhance the binding of vascular endothelial growth factor(VEGF)and basic fibroblast growth factor(bFGF)to their receptors on the cell membrane.These findings demonstrate that these structurally-tailored glycopolymers modulate the functions of EC adherent to materials and may be effective as modifiers for the promotion of endothelialization of cardiovascular implants.