USING MIXED SELF-ASSEMBLED MONOLAYERS PRESENTING RGD AND (EG)(3)OH GROUPS TO CHARACTERIZE LONG-TERM ATTACHMENT OF BOVINE CAPILLARY ENDOTHELIAL-CELLS TO SURFACES

This paper describes surfaces that promote the ligand-directed binding of cells and resist the cellular deposition of adhesive proteins. The se surfaces are based on self-assembled monolayers (SAMs) of alkanethi olates on gold that present mixtures of arginine-glycine-aspartate (RG D), a tripeptide that promotes cell adhesion by binding to cell surfac e integrin receptors, and oligo(ethyleneglycol) moieties, groups that resist nonbiospecific adsorption of proteins and cells. Surface plasmo n resonance (SPR) spectroscopy was used to measure the adsorption of c arbonic anhydrase and fibrinogen to mixed SAMs comprising RGD groups ( (EG)(6)OGRGD) and tri(ethylene glycol) groups ((EG)(3)OH); SAMs having values of the mole fraction of RGD (chi(RGD)) less than or equal to 0 .05 adsorbed nearly undetectable levels of carbonic anhydrase or fibri nogen. Bovine capillary endothelial cells attached and spread on SAMs at chi(RGD) greater than or equal to 0.00001, with spreading of cells reaching a maximum at chi(RGD) greater than or equal to 0.001. These m ixed SAMs reduced the deposition of proteins by attached cells relativ e to both fibronectin adsorbed on SAMs of hexadecanethiolate on gold a nd RGD peptide coated on glass. After allowing cells to attach for 2 o r 4 h to any of these surfaces presenting RCD groups, addition of solu ble GRGDSP to the medium contacting the adherent cells rapidly release d them from the surfaces. However, if cells were allowed to attach to surfaces for 24 h, only those cells attached to the mixed SAM presenti ng (EG)(6)OGRGD and (EG)(3)OH groups could be released using the solub le GRGDSP at a rate comparable to cells attached to fibronectin for 2 h. These results demonstrate that RCD alone is sufficient for adhesion and survival of cells over 24 h.