Protein adsorption on self-assembled monolayers induced by surface water molecule

Three types of self-assembled monolayers (SAMs) are employed for the investigation of protein adsorption. An octadecylsilane (ODS) SAM, a fluoroalkylsilane (FAS) SAM, and a polyethylene glycol (PEG) SAM are selected as examples. The amount of adsorbed protein is measured by fluorescent microscopy. A molecular dynamics (MD) simulation is carried out for modeling both the molecular structures of the SAMs and the water structure on the SAMs. A hydrophilic PEG SAM prevents protein adsorption, while a large amount of adsorption is observed on a hydrophobic ODS SAM. In spite of the hydrophobicity, an FAS SAM prevents protein adsorption as well as a PEG SAM. MD calculation suggests that the existence of surface-bound water on an ODS SAM induces protein adsorption. In the case of the FAS SAM, owing to the electrostatic interaction and the flexibility of the precursor, the water molecule is not bound to the surface and protein adsorption is suppresses.