Effect of Nano-to Micro-Scale Surface Topography on the Orientation of Endothelial Cells
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Effect of Nano-to Micro-Scale Surface Topography on the Orientation of Endothelial Cells
P. Uttayarat1, Peter I. Lelkes2, and Russell J. Composto1 1 Materials Science and Engineering Department, University of Pennsylvania, Philadelphia, PA 19104 U.S.A. 2 School of Biomedical Engineering, Science and Health Systems, Drexel University Philadelphia, PA 19104 U.S.A. ABSTRACT
The effect of grating textures on the alignment of cell shape and intracellular actin cytoskeleton has been investigated in bovine aortic endothelial cells (BAECs) cultured on a model cross-linked poly(dimethylsiloxane) (PDMS). Grating-textured PDMS substrates, having a variation in channel depths of 200 nm, 500 nm, 1 µm and 5 µm, were coated with fibronectin (Fn) to promote endothelial cell adhesion and cell orientation. As cells adhered to the Fn-coated surface, the underlying grating texture has shown to direct the alignment of cell shape, F-actin and focal contacts parallel to the channels. Cell alignment was observed to increase with increasing channel depths, reaching the maximum orientation where most cells aligned parallel to channels on 1-µm textured surface. Immunofluorescence studies showed that F-actin stress fibers and vinculin at focal contacts also aligned parallel to the channels. Cell proliferation was found to be independent of grating textures and the alignment of cell shape was maintained at confluence.
INTRODUCTION
The application of synthetic polymers as a non-degradable vascular substitute for bypass surgery often encounters problems of thrombogenicity and long-term patency, especially for graft diameters less than 6 mm [1]. Up to date, the approach to prevent thrombosis and to improve the biocompatibility of synthetic grafts is to introduce a functional monolayer of endothelial cells onto the graft surface [1]. This requires modifications of polymer surface such as adsorption with extracellular matrix (ECM) proteins [2-4] or covalent attachment with RGD
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peptide sequences [1,5-7] to promote cell adhesion. Additional to surface chemical composition, topographic textures of the surface also guides changes in the morphology and the orientation of adherent endothelial cells [4,8]. Alignment of cell shape and intracellular F-actin [8] as well as the formation of vinculin at focal adhesion sites [4] has been demonstrated in endothelial cells cultured on grating-textured surfaces. This grating-textured surface may provide an alternative method than flow in linear vessels [9] to achieve the structurally aligned and elongated endothelial cells. To investigate changes in cell morphology due to variation in channel depths, endothelial cells were cultured on grating-textured PDMS surfaces, having channel depths varied from 200 nm to 5 µm and lateral periodicity of 8 µm, and cell orientation as well as organization of F-actin and focal adhesion was evaluated.
EXPERIMENTAL PROCEDURES
Substrate Preparation Grating patterns were first fabricated onto silicon (Si) wafers, which subsequently served as molds to replicat
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