Gradient polymer surfaces for biomedical applications

The importance of biomaterials has been recognized in biomedical research for over three decades. Their practical utilization in biomedical applications depends on the appropriate physical and biological responses collectively referred to as biocompatibility. The response of biomaterials in a biological environment is characteristically associated with their surface properties. The modification of biomaterials by various surface treatments has recently become an active topic in surface engineering. A number of research groups have focused on the preparation of surfaces with a gradually varying chemical composition along one dimension. Such a "gradient surface" is of particular interest for basic and applied studies of the interactions between biological species and surfaces as the dependence of a selected property, such as wettability, on composition, can be examined in a single experiment on one surface. In this review, we describe the preparation and characterization of gradient polymer surfaces, presenting an organized and detailed overview of the state-of-the-art. First, the preparation of gradient surfaces and their characterization will be discussed. The introduction and characterizations of biofunctional groups on gradient surfaces will be then presented. Finally, we concentrate on the interactions of these surfaces with biological species, such as proteins and cells, important in the understanding of the basic science for biomedical application.