Variation in Tenacity of Protein Adsorption on Self-Assembled Monolayers with Monolayer Order As Observed by X-ray Reflectivity

Differences in the adsorption of human serum albumin (HSA) to hydrophobic self-assembled monolayers of hexadecyltrichlorosilane (HTS) with different layer packings have been observed using X-ray reflectivity. The monolayers with various thicknesses and electron density parameters were prepared using different deposition times. After the monolayers were exposed to 0.1 mg/mL solutions of HSA, a layer of albumin molecules was found adsorbed to the surface. When eluting with sodium dodecyl sulfate (SDS), all adsorbed protein was removed from the more densely packed surfaces. In contrast, a significant fraction of protein molecules adsorbed to less densely packed layers resisted elution with SDS. We conclude that more mobile, less densely packed HTS layers can better accommodate the albumin molecules, which results in more tenacious binding.