Attachment and morphology of adipose-derived stromal cells and exposure of cell-binding domains of adsorbed proteins on various self-assembled monolayers

Self-assembled monolayers (SAMs) of alkanethiols, 1-decanethiol (DT10), 11-mercapto-1-undecanol (MUOH), 11-mercapto-undecanoic acid (MUA), and 11-amino-1-undecanethiol (AUT), terminated with methyl (–CH3), hydroxyl (–OH), carboxyl (–COOH), and amino (–NH2) groups, were chemically adsorbed on Au and used as substrate surfaces. The features of the SAMs adsorbed on Au were characterized using physicochemical and depth-sensing nano-indentation methods. The ordering of various tail-group terminated SAMs on Au was associated with the rate of harmonic contact stiffness of the SAM molecules along with the measured displacement (MUA/Au < AUT/Au ≈ MUOH/Au < DT10/Au). However, the slight difference in nano-mechanical properties among SAMs/Au does not reach the variation required to induce cellular mechano-sensitive responses. Immunostaining analyses of cytoskeleton indicate that initial adipose-derived stromal cell (ADSCs) attachment and cell morphology on SAMs/Au was regulated by the surface chemistry. The effects of surface chemistry on the exposed cell-binding domains of adsorbed bovine fibronectin (bFN) and bovine vitronectin (bVN) under single-protein or multi-protein conditions were also examined to determine the most potent protein for ADSC attachement. The results reveal that under the single-protein condition, the exposed cell-binding domains of both bFN and bVN on SAMs/Au follow the sequence of tail-groups, –NH2, –COOH, –OH, and –CH3. However, SAMs with the tail-group –CH3 behaved significantly differently. Under the multi-protein condition, bFN domains showed a different sequence of tail-groups, –OH, –NH2 ≈ –COOH, and –CH3, whereas bVN domains showed the same sequence as that for the single-protein condition. Results of cell behavior and the exposed cell-binding domains of adhesive proteins suggest that vitronectin might be the fundamental adhesive protein for mediating ADSC attachment and spreading.