Protein adsorption and cell attachment to patterned surfaces

To better understand the events involved in the generation of defined tissue architectures on biomaterials, we have examined the mechanism of attachment of human bone-derived cells (HBDC) to surfaces with patterned surface chemistry in vitro. Photolithography was used to generate alternating domains of N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) and dimethyldichlorosilane (DMS). At 90 min after seeding, HBDC were localized preferentially to the EDS regions of the pattern. Using sera specifically depleted of adhesive glycoproteins, this spatial organization was found to be mediated by adsorption of vitronectin (Vn) from serum onto the EDS domains. In contrast, fibronectin (Fn) was unable to adsorb in the face of competition from other serum components. These results were confirmed by immunostaining, which also revealed that both Vn and Fn were able to adsorb to EDS and DMS regions when coated from pure solution, i.e., in the absence of competition. In this situation, each protein was able to mediate cell adhesion across a range of surface densities. Cell spreading was constrained on the EDS domains, as indicated by cell morphology and the lack of integrin receptor clustering and focal adhesion formation. This spatial constraint may have implications for the subsequent expression of differentiated function.