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There is much interest in attaching polyethylene glycol (PEG) and other hydrophilic, neutral polymers to surfaces to reduce the extent of protein and cell adsorption. Interestingly, these same surface-bound polymers are effective in masking surface charge and reducing electrokinetic effects such as particle electrophoretic mobility, streaming potential, and electroosmosis. It is apparent that similar molecular properties are responsible for both protein and cell rejection and reduction of electrokinetic effects. In this work we compared the fibrinogen-rejecting ability and the effect on electrophoretic mobility of three polymer coatings bound to polystyrene. The three polymers were side-bound dextran, end-bound dextran, and end-bound PEG. The results of these measurements were used to elucidate the importance of polymer packing density and polymer layer thickness on protein adsorption and reduction of electrokinetic effects. Protein adsorption appears not to be sensitive to polymer layer thickness or the presence of dilute polymer tails in a surface coating, while electrokinetic effects are. Protein adsorption is, however, very sensitive to the availability of exposed surface. Finally, the unique effectiveness of PEG is apparent in this research as in previous studies.

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