A new approach to the immobilisation of poly(ethylene oxide) for the reduction of non-specific protein adsorption on conductive substrates

Biomedical and biotechnological devices often require surface modifications to improve their performance. In most cases, uniform coatings are desired which provide a specific property or lead to a specific biological response. In the present work, we have generated pinhole-free coatings providing amine functional groups achieved by electropolymerisation of tyramine on highly doped silicon substrates. Furthermore, amine groups were used for the subsequent grafting of poly(ethylene oxide) aldehyde via reductive amination. All surface modification steps were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results indicate that the stability and the density of amine functional groups introduced at the surface via electropolymerisation compare favourably with alternative coatings frequently used in biomedical and biotechnological devices such as plasma polymer films. Furthermore, protein adsorption on amine and poly(ethylene oxide) coatings was studied by XPS and a colorimetric assay to test enzymatic activity. The grafting of poly(ethylene oxide) under cloud point conditions on electropolymerised tyramine layers resulted in surfaces with extremely low protein fouling character.