Simple poly(dimethylsiloxane) surface modification to control cell adhesion

In order to understand the influence of cell-adhesive molecules on anchorage-dependent cell behavior on biomaterial surfaces, a model system is required where these molecules can be applied to surfaces with controlled surface ligand density and resistance to the adsorption of additional proteins present in the medium. This study asked whether fibronectin could be immobilized in a controlled manner to a hydrophobic surface with a chemically modified triblock surfactant. ELISA studies indicated that variation of the soluble fibronectin concentration used for immobilization could be used to control the amount of fibronectin immobilized to the surface. Furthermore, fibroblasts seeded on these surfaces in 10% serum-containing medium attached and spread as a function of the amount of immobilized fibronectin. Surfaces treated with unmodified surfactant did not support cell attachment, suggesting that cell attachment and spreading were primarily regulated by the immobilized fibronectin with minimal interference from adsorption of serum proteins. Together, these results suggest that covalent immobilization to Pluronic F108 provides a method for studying cellular responses to cell adhesive proteins with little interference from competing adsorbates, even in the presence of complex biological fluids such as serum. This technique may be applicable to a variety of existing hydrophobic biomedical polymers as a basic science tool as well as for influencing cell behavior at implant interfaces.

The initial attachment of cultured bovine corneal epithelial cells and stromal fibroblasts to two oxygen-containing synthetic polymers was studied. Cultured epithelial cells and stromal fibroblasts were seeded onto two oxygen-containing surfaces: 'tissue culture' polystyrene (TCPS) and a polymer film deposited by RF plasma deposition using a methylmethacrylate monomer (MMA/FEP). To establish the mechanism of cell attachment, the effect of the selective removal of the vitronectin and fibronectin from the serum used in the culture medium was tested. The attachment of cultured epithelial cells during the first 90 min of culture was reduced by 40% (TCPS)-80% (MMA/FEP) as a result of removing vitronectin from the medium. Attachment of these cells to TCPS was reduced by 85-95% when the serum was depleted of both fibronectin and vitronectin. However, depletion of fibronectin reduced cell attachment to TCPS by 20%, whilst on MMA/FEP cell attachment was equivalent, or higher, than that for intact serum. The attachment of cultured corneal stromal fibroblasts was similarly dependent on vitronectin but less dependent on fibronectin. Therefore, for the attachment of both cultured epithelial cells and fibroblasts to oxygen-containing surfaces in the presence of serum, there is a high requirement for serum vitronectin but a lesser requirement for fibronectin. The effects of the establishment of corneal epithelial cells in culture and the site of origin of the cells, were determined. Primary isolates of epithelial cells isolated from the limbal, central or peripheral regions of the cornea were less dependent on vitronectin for initial attachment to TCPS than were these cells after several passages in culture. Furthermore, the primary isolates were dramatically less responsive to vitronectin than the cultured cells. These results indicate that the mechanism of attachment of corneal epithelial cells to TCPS varies with the culture experience of the cells. Cells that are culture neophytes can employe endogenous mechanisms for the initial attachment to TCPS, whereas cells established in culture are dependent on exogenous vitronectin in order to attach.