Endothelial cell interactions with model surfaces: effect of surface chemistry, surface mobility, and the adsorbed protein layer
The clinical success of the small diameter vascular graft remains limited due to occlusion resulting from thrombus formation. Methods for promoting graft endothelialization have been investigated to improve graft healing. A common requirement of these methods is a substrate that will promote endothelial cell growth.The effects of substrate surface properties on bovine aortic endothelial cell (BAEC) growth and protein adsorption were investigated using self-assembled monolayers (SAMs) of alkane thiols on gold. Surface properties studied were surface chemistry (type, concentration, and spatial arrangement of surface chemical functionalities) and surface molecular mobility. Adsorbed protein layers were characterized to determine the composition and binding strength (measured by SDS elutability) of three serum proteins.BAEC growth varied with surface chemical functionality. BAEC growth was significantly higher on COOH SAMs than on CH3 or OH-terminated SAMs. BAEC growth on binary composition SAMs varied significantly with functional group concentration. Cell growth increased with increasing COOH content, peaked at 50--60% COOK then remained constant as COOH content increased. BAEC growth can be controlled by the surface concentration of growth-promoting functional groups. The effect of functional group arrangement on cell growth was significant in the early phase of cell growth but diminished with increasing culture time. The effect of surface mobility on cell growth was limited.Adsorbed protein layer composition varied significantly with binary SAM surface composition. Albumin and vitronectin adsorption levels were equivalent and were significantly higher than fibronectin adsorption. The elutability of albumin and fibronectin did not vary consistently with surface COOH content. Vitronectin elutability increased with increasing COOH content, peaked at 50--60% COOH, then remained constant with increasing COOH content. Comparing cell growth results with adsorbed protein layer characteristics, adhesive protein surface fraction (fibronectin and vitronectin) and vitronectin elutability varied with COOH content in a manner similar to cell growth. The promotion of BAEC growth was correlated with increased adhesive protein surface fraction and vitronectin elutability.In this research, several substrate properties and adsorbed protein layer properties associated with the promotion of endothelial cell growth were identified. This information may aid in the design of implant surfaces that guide a specific biologic response.
- Bioengineering