Comparison on protein adsorption properties of diamond-like carbon and nitrogen-containing plasma polymer surfaces

In this paper, the surface and functional protein binding properties of the diamond-like carbon (DLC) and nitrogen-containing plasma polymer (NPP) surfaces were compared using techniques such as X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), enzyme-linked immunosorbent assay (ELISA) and enzyme activity assays. The NPP surfaces were more similar to proteins in respects of their composition and surfaces energies, which are preferred to accommodate immobilized proteins in a more natural manner to retain their bioactivity. The EPR analysis suggested that the radicals in the NPP surfaces could more readily participate in the covalent immobilization of proteins, consistent with the ELISA and XPS analysis result that the NPP surface had approximately double covalent coverage immobilized protein compared with the DLC surface. The enzyme activity assay showed better retention of protein bioactivity for immobilized horseradish peroxidise on the NPP surface, resulting from its more similar physical and chemical properties to protein immobilized surfaces. For applications requiring a high degree of covalent immobilization of bioactive proteins and extended retention of bioactivity, the NPP surface is clearly preferred. (C) 2011 Elsevier B.V. All rights reserved.