Application of layer-by-layer coatings to tissue scaffolds - development of an angiogenic biomaterial.

Tissue engineered materials aimed at wound care typically underperform due to poor engrafting to the wound bed. The need for such materials will continue to intensify as a result of an ageing population and an increase in patients suffering from vascular problems. Here we describe the development of an angiogenic coating strategy employing a combination of plasma phase deposition of acrylic acid and layer-by-layer (LBL) chemistry using polyethyleneimine and poly(acrylic acid) for the immobilization of heparin and Vascular Endothelial Growth Factor (VEGF). The formation of the coating and its ability to immobilize heparin was examined by Quartz Crystal Microbalance with Dissipation. X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy were used to confirm that these coatings retained a significant amount of heparin on the surface when applied to a flat substrate. The coating strategy was transferred to 2 different tissue scaffold architectures: a commercially available non-biodegradable polypropylene mesh, and a biodegradable electrospun poly(lactic-co-glycolic acid) (PLGA) scaffold. XPS confirmed that the coating was successfully applied to the scaffolds and that a similar amount of heparin was immobilized. In vitro testing showed that while HDMEC readily attached to the PLGA scaffold, they were inhibited from adhering and forming proliferative colonies where heparin alone was attached to the LBL coated PLGA scaffold. However, after dip coating with VEGF, the heparin coated scaffold supported both attachment and colony growth of HDMEC; no such colony formation occurred in the absence of VEGF.