Protein—surface interactions in the presence of polyethylene oxide: II. Effect of protein size

Abstract

Polyethylene oxide (PEO) surfaces exhibit low protein adsorption. PEO surface—protein interactions are examined theoretically as a function of surface density and chain length of PEO and variation in the size of the protein (assumed to be a sphere). Recent studies suggest that the PEO surface may have a small hydrophobic character. We study the effect of surface density of PEO and protein size and deduce the PEO surface density conditions for optimal protein resistance. For small proteins ( R ∼ 20 A ̊ ), D should be small (∼ 10 Å), while for large proteins ( R ∼ 60–80 A ̊ ), D should be larger (∼ 15 Å), where R is the protein radius and D is the average distance between end-attached PEO chains. These results evolve from the trade-offs between steric repulsion and the assumed weak hydrophobic interaction between the PEO layer and the protein. The longest chain length of PEO at optimum surface density appears best for protein resistance. As a number of assumptions and estimates are involved in the model, the results can be taken only as qualitative trends at this time. The trends should be helpful in the design and evaluation of surfaces resistant to protein adsorption.