Effect of Nano- to Micro-scale Surface Topography on the Orientation of Endothelial Cell

Abstract

A model vascular graft of cross-linked polydimethylsiloxane (PDMS) has been modified with protein and varied topographically to promote endothelial cell attachment as well as to guide cellsubstrate interactions.  PDMS with a smooth surface (RMS roughness ~ 0.5 nm) and grating-textured surfaces, having channel depths of 100 nm, 500 nm, 1 µm and 5 µm, and lateral width of 4 µm, are fabricated.  While the pre-adsorbed fibronectin promotes cell adhesion, the underlying topographic features provide a contact guidance that influences cell morphology and cell orientation.  Using phase contrast microscopy after seeding cells for 1, 4, 24 and 48 h, cell elongation and alignment parallel to the grating direction increases monotonically with increasing channel depth, reaches maximum orientation at 1 µm, and then slightly decreases at 5 µm.  By fluorescence staining of F-actin and vinculin, cytoskeleton and focal contacts are observed to preferentially orient parallel to the grating direction on textured surfaces having depths of 1 and 5 µm.  Confocal and scanning electron microscopies show that cell protrusions extend into channels and also along the side walls of the channels.  Cell proliferation is found to be independent of surface topography.  Relevant to tissue engineering applications, cell orientation is retained at confluence on textured PDMS surfaces.  Using surface topography to create contact guidance provides an alternative pathway to obtain endothelial cell alignment, similar to flow in the natural blood vessel.