Amphiphilic networks

Abstract

The surface energetics, specifically the balance of polar/nonpolar forces on the interfaces of various amphiphilic networks comprising hydroxyethyl methacrylate (HEMA) or N,N-dimethylacrylamide (DMAAm) hydrophilic chains linked by polyisobutylene (PIB) hydrophobic chains (for brevity H and A networks) in contact with water have been studied by dynamic contact angle measurements. Both networks show large contactangle hysteresis due to surface heterogenity and surface rearrangements. The balance of the polar/nonpolar forces of the dry networks, as quantitated by the I_p/W_A ^d ratio is much below unity; upon equilibrating in water the I_p/W_A ^d ratio increases but remains below unity. Protein adsorption from human plasma and human monocyte adhesion to A and H amphiphilic networks possessing polar/nonpolar ratios lower than unity have been investigated. Both networks adsorb less fibrinogen, albumin and Hageman factor (factor XII) than glass, polyethylene (PE), and polydimethylsiloxane (PDMS). The extent of adsorption of factor VIII on A, H and glass are very similar. Adsorption of IgG on A was appreciable, however, on H it was less than on any of the other surfaces studied. Monocyte adhesion was significantly inhibited on both networks and glass, relative to a positive adhesive surface such as tissue culture polystyrene (TCPS). Evidently both the A and the H networks exhibit reduced protein adsorption and cell adhesion which indicates biocompatibility of these networks at blood contacting surfaces. The ratio of the polar/nonpolar forces expresed by the I_p/W_A ^d ratio may be useful to predict low protein adsorption and cell adhesion on polymer surfaces.