Modulating cell adhesion and spreading by control of FnIII7–10 orientation on charged self‐assembled monolayers (SAMs) of alkanethiolates

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Abstract
In this work, we demonstrate that surface charge can be used to modulate cell adhesion/spreading through the control of the orientation of adsorbed FnIII7–10, which is a cell‐adhesive protein containing RGD residues. Carboxylic acid (COOH) and amine (NH2)‐terminated self‐assembled monolayers (SAMs) of alkanethiolates were used as model negatively and positively charged surfaces, respectively. The adsorbed amount of FnIII7–10 is controlled to be equivalent on both SAMs as confirmed by the adsorption isotherms determined using I125‐radiolabeled FnIII7–10. The binding of a monoclonal antibody specific for the cell‐binding domain of FnIII7–10 was measured by surface plasmon resonance (SPR) to evaluate FnIII7–10 orientations on different SAMs. Results indicate that adsorbed FnIII7–10 on NH2‐SAM has an orientation with more cell‐binding domains accessible than on COOH‐SAM, confirming our predictions from Monte Carlo simulations. Both phase contrast images and Vybrant® MTT cell proliferation assays show that the adhesion/spreading of bovine aortic endothelial cells (BAECs) on the NH2‐SAM is significantly better than that on the COOH‐SAM coated with an equivalent amount of FnIII7–10. These results indicate that surface charge can be used to specifically orient cell adhesive proteins such as FnIII7–10, thus providing a promising strategy to increase the activity of materials incorporating biological moieties. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006

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