Mechanism(s) of enhanced vascular cell response to polymeric biomaterials with nano-structured surface features.

摘要

Creating nanometer surface topographies on ceramics, metals, polymers, and composites thereof significantly improves the functions of some cells (such as osteoblasts, chondrocytes, smooth muscle cells, and neurons). Specifically, poly(lactic-co-glycolic acid) (PLGA) films with a nanometer surface topography promote vascular endothelial and smooth muscle cell adhesion. The objective of this in vitro research was to begin to understand the mechanisms underlying this observed increased vascular cell adhesion. For this purpose, PLGA substrates of various surface feature dimensions were exposed to serum-containing media to probe initial protein interactions that may influence subsequent vascular cell adhesion. The initial adsorbed protein layer was identified using SDS-PAGE and ELISA techniques. Results provided evidence that PLGA (both nano-structured and conventional, or those not possessing nanometer surface features) adsorbed significant quantities of both vitronectin and fibronectin from serum. Furthermore, results indicated that nano-structured PLGA adsorbed significantly more vitronectin and fibronectin when compared to conventional PLGA. When separately pre-adsorbing both vitronectin and fibronectin, increased vascular smooth muscle and endothelial cell density was observed on nano-structured (compared to conventional) PLGA. Additionally, vascular cell inhibition studies provided evidence that vitronectin and fibronectin possess different conformations (or bioactivity) on nano-structured surfaces compared to conventional surfaces. These results were supported by AFM analysis of fibronectin adsorption to PLGA films. Results indicated that fibronectin adsorbed in discrete linear patterns on cast nano-structured PLGA, while fibronectin adsorption on conventional PLGA showed no specific pattern.; The final objective of the present study was to analyze fibronectin adsorption and vascular cell adhesion to PLGA surfaces with controlled topographies. Poly(dimethysiloxane) (PDMS) casting techniques were utilized to create templates of polystyrene (PS) nano-particle arrays. PLGA films cast onto these templates created features similar to the original PS arrays. Results from fibronectin adsorption and vascular cell adhesion to these surfaces showed that the 200 nm PLGA surface had extended fibronectin structures and improved vascular smooth muscle and endothelial cell adhesion compared to smooth controls.; Taken together, the results of the present in vitro study provided evidence that cell adhesive proteins adsorbed in different quantities, and possibly conformations, on nano-structured compared to conventional PLGA topographies; this may in part, account for increased vascular cell adhesion on nano-structured PLGA. In this manner, the present study continues to provide evidence of the promise of nano-structured PLGA for vascular tissue engineering applications.