ABSTRACT
References ...................................................................................................................................... 523
Surface properties of materials are the key parameters in the interaction between an implanted device and the host tissue (Chen et al. 2008; Xu and Siedlecki 2009). Hydrophobicity or hydrophilicity of a material is usually expressed as surface wettability and determines protein adsorption, platelet adhesion, and cell and bacterial adhesion (Xu and Siedlecki 2007) and also their subsequent structural and biological activity (Hylton et al. 2005; Wu et al. 2005b). Hydrophobic surfaces, namely poorly wettable, tend to absorb proteins in a greater proportion than hydrophilic surfaces, namely highly wettable. In hydrophilic surfaces, repulsive solvation forces arising from strongly bound water occur (Israelachvili and Wennerstrom 1996; Noh and Vogler 2006). A stark transition between protein adherent and protein nonadherent materials has been found to happen on water contact angles 60°–65° (Xu and Siedlecki 2007), which is consistent with the appearance of hydrophobic interactions (Yoon et al. 1997). However, surface wettability seems not to be the only parameter affecting the adhesion of proteins. The phenomenum of protein adhesion is rather a competition between the hydrophobic effect and the dehydration of the surface. The former one expels proteins from solution but proteins will only be adsorbed on a surface when the energy necessary for dehydrating the surface is lower, i.e., ΔG0 (Phobic effect) > ΔG0 (dehydration) (Noh and Vogler 2006). The hydrophobic effect is the energy that expels protein from solution to recover hydrogen bonds among water molecules otherwise separated by proteins.
