Study of single protein adsorption onto monoamino oligoglycerol derivatives: a structure-activity relationship

This paper describes a structure-property study of mixed self-assembled monolayers (SAMs) on gold that present methylated or hydroxyl-terminated polyglycerol (PG) structures that vary in size and architecture, and their ability to resist the adsorption of four test proteins from solution. Mixed SAMs were prepared by the reaction of an amine of the polyglycerol structures with a SAM that presents interchain anhydrides (the anhydride method). Surface plasmon resonance spectroscopy was used to measure the adsorption of fibrinogen, lysozyme, albumin, and pepsin to the resulting mixed PG amide/carboxylate-terminated SAMs. In addition, FTIR infrared reflection-absorption spectroscopy (IRRAS) and contact angle goniometry were used to characterize the mixed SAMs. The study showed that even though methylation increases the hydrophobicity of these mixed PG SAMs, it greatly improved their ability to resist the adsorption of the test protein with the best performing surface demonstrating better resistance than a mixed SAM that presented poly(ethylene glycol) (PEG350). It was also shown that increasing the molecular weight of the PG structures (oligomer length or higher dendritic generations) generally resulted in decreased protein adsorption. With respect to the architecture, the linear oligoglycerols showed better resistance than their equal weight branched dendrons, while hyperbranched dendrons were more resistant to protein adsorption than perfect dendrons of equal weight.