Consequences of Hydrocarbon Contamination for Wettability and Protein Adsorption on Graphite Surfaces

Abstract

We present results from molecular dynamics simulations and contact angle measurements on graphite showing that this surface is indeed intrinsically mildly hydrophilic contrary to the common belief. Hydrocarbon contamination, known to be the source for the usually observed hydrophobic property of graphite, also affects protein adsorption processes as shown in this study. In the computational part of this work ethane was used as a model hydrocarbon which acts on the surface by reducing the water–surface and protein–surface interactions. This contamination then results in higher water contact angles. The process of protein adsorption is studied for the example of insulin revealing a reduction in adsorption strength despite the surface being more hydrophobic when contaminated. Although the proteins did not denature on the contaminated surfaces, further processes, such as the displacement of hydrocarbons by the protein, may occur on a longer time scale. In conclusion, we argue that proteins adsorb faster on pure than on contaminated surfaces with respect to the molecular dynamics time scale of ns.