The interaction of proteins and cells with self-assembled monolayers of alkanethiolates on gold and silver

Abstract

Alkanethiols, HS(CH 2) n X, chemisorb on gold and silver and form self-assembled monolayers (SAMs). The ability to present a variety of functional groups, X, at the terminal position of the alkanethiol makes it possible to control the structure of the surface at the molecular level, and thus to control the interfacial properties of these organic surfaces. These SAMs constitute an exceptionally useful set of model surfaces with which to study the interaction of synthetic materials with biologically relevant systems. By varying the terminal group X, it is possible to examine the influence of the structure and polarity of common organic groups on the adsorption of proteins. Alkanethiols terminated with oligo(ethylene glycol) groups form SAMs that resist the adsorption of proteins (so-called ‘inert surfaces’). These alkanethiols, when used in mixed SAMs that include alkanethiols that present other functional groups, isolate the biomolecular interactions of interest from non-specific effects and simplify fundamental studies of protein adsorption. Surface plasmon resonance (SPR) is a particularly valuable technique for measuring rates and equilibrium constants of processes that involve adsorption of proteins at surfaces and for characterizing mechanisms of protein adsorption. Since the techniques used in preparing SAMs for studies of protein adsorption are essentially the same as those used in preparing substrates for SPR, a common synthetic technology can be used with both. Soft lithographic techniques—microprinting and micromolding—make it possible to pattern SAMs with different functionalities on surfaces that can be either planar or contoured. The combination of SAMs, inert surfaces, SPR, and soft lithography allows the study of the molecular-level interaction of solutions containing proteins with synthetic surfaces. Extensions of these studies to investigations of the attachment and spreading of cells on surfaces also offer a new set of research tools in cell biology.