Self-assembled monolayers with different terminating groups as model substrates for cell adhesion studies

Abstract

Cell shapes induced by cell–substratum interactions are linked with proliferation, differentiation or apoptosis of cells. To clarify the relevance of specific surface characteristics, we applied self-assembled monolayers (SAM) of alkyl silanes exhibiting a variety of terminating functional groups. We first characterised the SAMs on glass or silicon wafers by measuring wettability, layer thickness and roughness. Water contact angle data revealed that methyl (CH 3), bromine (Br), and vinyl (CH=CH 2) groups lead to hydrophobic surfaces, while amine (NH 2) and carboxyl (COOH) functions lead to moderately wettable surfaces, and polyethylene glycol (PEG) and hydroxyl (OH) groups created wettable substrata. The surfaces were found to be molecular smooth except for one type of NH 2 surface. The SDS-PAGE analysis of proteins adsorbed from bovine serum to the SAMs showed less protein adsorption to PEG and OH than to CH 3, NH 2 and COOH. Immunoblotting revealed that a key component of adsorbed proteins is vitronectin while fibronectin was not detectable. The interaction of human fibroblasts with CH 3, PEG and OH terminated SAMs was similarly weak while strong attachment, spreading, fibronectin matrix formation and growth were observed on COOH and NH 2. The strong interaction of fibroblasts with the latter SAMs was linked to an enhanced activity of integrins as observed after antibody-tagging of living cells.