Adsorption of immunoglobulin G to plasma-co-polymer surfaces of acrylic acid and 1,7-octadiene

Functionalised thin films of copolymers of acrylic acid and 1,7-octadiene have been deposited by plasma-co-polymerisation to create a range of surfaces of well-defined chemistry, containing carboxyl functional groups. X-Ray photoelectron spectroscopy (XPS) has been used to characterise the deposits. Adsorption of immunoglobulin G from single solution has been studied by indirect, antibody detection (ELISA), and by direct, radio-labelling and fluorescent detection methods. In addition, XPS analysis of the surface adsorbed protein was also performed. Direct measurement techniques showed an apparent decrease in protein binding on carboxylic acid functionalised surfaces, whilst antibody detection showed an increase in binding with increased carboxylic acid content of the surface. This difference has been ascribed to orientational/conformational and/or packing differences of the proteins on the different surfaces, leading to an increased biological ("functional'') activity on the carboxylic acid functionalised surfaces. Adsorption of IgG from serum has also been probed by ELISA. An increase in IgG binding with surface carboxylic acid content was measured, indicating a similar effect when IgG is adsorbed from a complex protein mixture.