Regulating Coupling Efficiency of REDV by Controlling Silk Fibroin Structure for Vascularization.

Controlled and rapid vascularization of engineered tissues remains one of the main challenges for tissue engineering. The immobilization of peptides and other bioactive molecules on the scaffolds has been demonstrated to be able to improve vascularization. However, the density of peptides modified on the scaffold surface is an important factor influencing vascularization. Thus, regulating the coupling efficiency of peptides may be an effective way to adjust vascularization. In this study, two-dimensional (2D) silk fibroin (SF) films and three-dimensional (3D) porous SF scaffolds with different secondary structure were prepared and coupled with Arg-Glu-Asp-Val (REDV) peptide. Compared with the high crystalline scaffolds, more peptides were bound on the scaffolds with low crystalline both in 2D and 3D forms with the result that more endothelial cells adhered on the low crystalline SF scaffolds. In addition, the in vivo angiogenic assays demonstrated that the low crystalline scaffolds showed higher blood vessel density after 28 days of implantation, which was 1.4-times as much as that of the high crystalline group. The results indicated that the peptide density could be controlled by SF structure and that the low crystalline SF scaffolds modified with REDV peptide could be a potential candidate for inducing angiogenesis in tissue engineering applications.