Characterization of a self-assembled monolayer of O-(2-Mercaptoethyl)-O′-methyl-hexa(ethylene glycol) (EG7-SAM) on gold electrodes

Abstract

The modification of surfaces by polyethylene glycol (EGn) is an approach used to reduce the antifouling effects of these materials in a biological medium. It has been found that the packing density and conformational order of these molecules in the films are crucial for the inhibition of unspecific protein adsorption. In this work, we present a study of the formation and characterization of a self-assembled monolayer of O-(2-Mercaptoethyl)-O′-methyl-hexa(ethylene glycol) (EG7-SAM) on either poly-oriented or Au(111) single crystal surfaces. The final properties of the formed EG7-SAMs are studied by examining the reductive desorption process as well as the electronic and ionic blocking behaviour of these layers, under different experimental conditions, by using cyclic voltammetry and electrochemical impedance spectroscopy. Additional information of the structure, composition and organization is obtained by absorption-reflection infrared and X ray photoelectron spectroscopies and contact angle measurements. In contrast to the behaviour observed with alkanethiols, the EG7-SAM shows the best final organization at a modification time of 1 h. The antifouling properties of this EG7-SAM against the adsorption of the bovine serum albumin protein in a phosphate saline medium, has been evidenced by using the electrochemical quartz crystal microbalance technique.