A correlation study of protein adsorption and cell behaviors on substrates with different densities of PEG chains

The adsorption of proteins, in particular fibronectin (Fn), was studied on poly(ethylene glycol) (PEG, 5 kDa)-grafted surfaces, and was correlated with the adhesion behaviors of smooth muscle cells (SMCs). The PEG molecules were covalently grafted on aldehyde-activated substrates with different densities of amino groups. The thickness of PEG layer increased nearly 10 fold in a hydrated state, reaching to 27 nm on the surface of highest PEG chain density with a brush configuration. On the lower PEG-grafted surfaces, however, the PEG molecules adopted a mushroom configuration. The adsorption of Fn without and with the competition of bovine serum albumin (BSA) and serum was studied by using ellipsometry, fluorescence microscopy and radio-labeling techniques. The adsorption amount of Fn in serum decreased initially with increased PEG chain density until 0.12 chains/nm2 PEG, and then slightly increased on the 0.29 chains/nm2 PEG. A series of protein preadsorption experiments were carried out under different conditions before SMCs culture in vitro. Compared with those substrates without Fn preadsorption, the cell adhesion and spreading were significantly enhanced on all the PEG surfaces preadsorbed with Fn and serum, although they overall decreased along with the increase of PEG grafting density. The adhesion force of Fn decreased monotonously with the increase of PEG grafting density, which was in accordance with the cell adhesion force. The correlation between the PEG-grafted surfaces, Fn adsorption, and cellular behaviors is finally suggested.