Thiol-ene conjugation of a VEGF peptide to electrospun scaffolds for potential applications in angiogenesis

Vascular endothelial growth factor (VEGF) plays a vital role in promoting attachment and proliferation of endothelial cells, and induces angiogenesis. In recent years, much research has been conducted on the func-tionalization of tissue engineering scaffolds with VEGF or a VEGF-mimetic peptide to promote angiogenesis. However, most chemical reactions are nonspecific and require organic solvents, which can compromise control over functionalization and alter peptide/protein activity. An attractive alternative is the fabrication of functio-nalizable electrospun fibers, which can overcome these hurdles. In this study, we used thiol-ene chemistry for the conjugation of a VEGF-mimetic peptide to the surface of poly (epsilon-caprolactone) (PCL) fibrous scaffolds with varying amounts of a functional PCL-diacrylate (PCL-DA) polymer. 30% PCL-DA was selected due to homoge-neous fiber morphology. A VEGF-mimetic peptide was then immobilized on PCL-DA fibrous scaffolds by a light -initiated thiol-ene reaction. 7-Mercapto-4-methylcoumarin, RGD-FITC peptide and VEGF-TAMRA mimetic pep-tide were used to validate the thiol-ene reaction on the fibrous scaffolds. Tensile strength and elastic modulus of the 30% PCL-DA fibrous scaffolds were significantly increased after the reaction. Conjugation of the 30% PCL-DA fibrous scaffolds with the VEGF peptide increased the surface water wettability of the scaffolds. Patterned structures could be obtained after using a photomask on the fibrous film. Moreover, in vitro studies indicated that scaffolds functionalized with the VEGF-mimetic peptide were able to induce phosphorylation of the VEGF receptor and enhanced HUVECs survival, proliferation and adhesion. A chick chorioallantoic membrane (CAM) assay further indicated that the VEGF peptide functionalized scaffolds were able to promote angiogenesis in vivo. These results show that scaffold functionalization can be controlled via a simple polymer mixing approach, and that the functionalized VEGF peptide-scaffolds have potential for vascular tissue regeneration.