Protein adsorption to oligo (Ethylene Glycol) self assembled monolayers with amide linkage experiments with fibrinogen, heparinised plasma and serum

Abstract

Low protein adsorption is believed advantageous for blood-contacting materials and ethylene glycols (EG)-based polymeric compounds are often attached to surfaces for this purpose. In the present study, the adsorption of brinogen, serum, and plasma were studied by ellipsometry on a series of well-de ned oligo(EG) terminated alkane-thiols self-assembled on gold. The layers were prepared with compounds of the general structure HS-(CH2)15-CONH-EGn, where n D 2, 4, and 6. Methoxy-terminated tri(EG) undecanethiol and hydroxyl-terminated hexadecanethiol self-assembled monolayers (SAMs) were used as references. The results clearly demonstrate that the adsorption depends on the experimental conditions with small amounts of brinogen adsorbing from a single protein solution, but larger amounts of proteins from serum and plasma. The adsorption of brinogen and blood plasma decreased with an increasing number of EG repeats and was temperature-dependent. Signi cantly less serum adsorbed to methoxy tri(EG) than to hexa(EG) and more proteins remained on the latter surface after incubation in a sodiumdodecyl sulfate (SDS) solution, indicating a looser protein binding to the methoxy-terminated surface. All surfaces adsorbed complement factor 3 (C3) from serum and plasma, although no surfacemediated complement activationwas observed. The present study points to the importance of a careful choice of the proteinmodel system before general statements regardingthe protein repellantproperties of potential surfaces can be made.