Adsorption of vitronectin, collagen and immunoglobulin-G to plasma polymer surfaces by enzyme linked immunosorbent assay (ELISA)

Abstract

Polymeric functional thin films have been deposited from plasmas of allyl alcohol, acrylic acid, allylamine and octa-1,7-diene onto polystyrene microwells and aluminium foil, and analysed by X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. The films were found to be conformal and pin-hole free. Advancing and receding water contact angles measured in air showed that the surfaces had a range of hydrophilicities. The adsorption of human vitronectin, human immunoglobulin G (IgG) and heat-denatured bovine type II collagen to the different plasma polymer surfaces from single solutions was compared by enzyme linked immunosorbent assay (ELISA). Results demonstrate that the adsorption of proteins depends not only on the chemistry of the surface, but also on the nature of the protein. Vitronectin adsorbed most extensively to the acrylic acid-deposited surface, while immunoglobulin G adsorbed more readily to the allylamine deposited surface. The functionalised surfaces performed poorly in terms of collagen binding, with much higher levels of adsorption to the hydrocarbon (octa-1,7-diene) plasma polymer, and the uncoated polystyrene control wells. The amount of adsorbed protein detected on a surface is often explained in terms of surface hydrophilicity/hydrophobicity. The results of this study show that adsorption of these proteins is not simply a matter of wettability, but relates more to the chemical functionality of the surface, which in turn affects a number of surface properties, including wettability, surface charge and pK_a.