Nanometric Surface Patterns for Tissue Engineering: Fabrication and Biocompatibility in Vitro
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Nanometric Surface Patterns For Tissue Engineering: Fabrication And Biocompatibility In Vitro M Riehle*1, M Dalby1, H Johnstone3, J Gallagher1, M A Wood1, B Casey2, K McGhee2, S Affrossman3, C D W Wilkinson2 and A S G Curtis1 1 Centre for Cell Engineering, IBLS, University of Glasgow, Glasgow, UK; 2Department of Electronic Engineering, University of Glasgow, Glasgow, UK; 3Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, UK. ABSTRACT Three fundamentally different methods were used to fabricate nanometric surface features on polymers or fused silica. Phase separation of binary polymer mixes resulted in randomly distributed features whose depth and shape could be tightly controlled over large areas. Colloidal resist patterned large areas randomly and uniformly with very fine spikes. In contrast e-beam and reactive ion etching were used to create a set of regular spaced pillars on an orthogonal pattern. Some of the surfaces were replicated by in situ polymerization, solvent casting, embossing or melt molding onto polystyrene (PS) or ε−poly caprolactone (ε−PCL). Nanometric features down to 60nm were imprinted onto the polymers with high fidelity. Cells were seeded onto the nanometric surfaces and adhesion, morphology and cytoskeleton investigated. Cells respond to regular features of 170/80nm (width/depth) with reduced adhesion and changes in overall morphology and cytoskeleton. Small nanofeatures (13nm, 35nm depth) made by phase separation on the other hand increased adhesion and promoted cytoskeletal differentiation. The responses of the cells are indicative that nanometric surface features are useful modifications on scaffolds for tissue engineering or on medical implants. INTRODUCTION The manufacturing methods developed primarily for the electronic industry have been successfully applied to pattern biomaterial surfaces at the micro- and the nanoscale. Micrometric surface features such as grooves or patterned chemistry have previously been used to "engineer" gross- and intracellular morphology as well as cell behavior and even cell survival [1-3]. The reported effects of artificial sub micron structures on cells are less straightforward: regular nanopillar arrays reduced adhesion and spreading [4], nanometric grooves guide cells and align their cytoskeleton [5], nanometric cliffs increased adhesion [6] and two cell types reacted differentially to “silicon grass” [7]. Experiments using copies of natural nanometric surfaces [8], intended to disentangle the effects of topography from those of chemistry, showed that replica of the extracellular matrix (ECM) promoted adhesion and cell spreading. These effects are relevant for tissue engineering (TE) since in its classic approach e.g. [9] TE aims to generate a tissue with a specific function from a stem cell or an organotypic cell population grown in a natural or an artificial ECM. Therefore a means to signal to the cells where to adhere and how to develop is advantageous. Permanent topographic surface features of nanometric dimensions could be
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