Construction of cytokine reservoirs based on sulfated chitosan hydrogels for the capturing of VEGF in situ.

Nutrients and oxygen are delivered mainly by blood vessels to nourish the cells and tissues in the body. Thus, biomaterials are processed by loading cytokines, such as vascular endothelial growth factors (VEGF), to facilitate angiogenesis in order to accelerate tissue regeneration. Nevertheless, the unpredictable biosecurity of exogenous cytokines is still a controversial issue for its clinical application. In this study, we constructed a kind of cytokine reservoir utilizing the binding affinity between heparin-like sulfate polysaccharide and endogenous growth factors. Two types of sulfated chitosan hydrogels, namely 6-O-sulfated chitosan (6-O-SCS) and 2-N,6-O-sulfated chitosan (2-N,6-O-SCS) hydrogels, were formed on the surface of the gelatin sponge matrix. The microstructure of the SCS-coated scaffolds is porous and interconnected, which is beneficial for cellular infiltration. Besides, human umbilical vein endothelial cells (HUVECs) can adhere and proliferate well on the surface of the scaffolds. Notably, sulfated chitosan-coated scaffolds exhibit an ability to capture VEGF in vitro & vivo, especially for the 2-N,6-O-SCS-coated scaffold. It is also verified by mice models that sulfated chitosan-coated scaffolds result in a concentrated VEGF microenvironment in specific domains as cytokine reservoirs and induce mass microvessels after implantation into subcutaneous tissues. As such, the sulfated chitosan-coated scaffolds served as VEGF reservoirs to accelerate angiogenesis and wound healing. This beneficial strategy may be applicable to in situ tissue regeneration by capturing more cytokines and promoting healing.