Investigating cell adhesion to controlled surface chemistry via self-assembly of binary composition alkylthiol monolayers, streptavidin immobilization, and cell receptor ligand attachment

Abstract

A method of controlling surface chemistry for immobilizing biofunctional ligands for studying in vitro cell response is described. Binary composition self-assembled monolayers (SAMs) of a biotinylated and either an oligo(ethylene oxide) or methylene-terminated alkylthiolate deposited on gold-coated substrates are used to bind streptavidin. Maximal streptavidin adsorption and stability was quantitated and optimized by varying the identity and ratio of the thiolates in the mixed SAMs. The streptavidin coated surfaces were shown to support additional biotinylated ligand adsorption. Sequential biotinylated ligand adsorption is also possible, with the maximum amount of both 1igands determined by the streptavidin coverage, which defines the number of available binding sites. The immobilized ligands were used to support adhesion-dependent cell attachment. The attachment was shown to be specific to the identity of the immobilized ligand and to the conjugate cell surface receptor. These substrates can be used to quantitatively immobilize a wide range of ligands with specificity, selectivity, and stability, and the selectively modified substrates can be used as a well-controlled and characterized model system to study the interaction between adhesion-dependent cells in culture to the immobilized ligands.