Cellular Responses on a Wettability Gradient Surface with Continuous Variations in Surface Compositions of Carbonate and Hydroxyl Groups

Abstract

This article reports adhesion, spreading, migration, and proliferation responses of bovine endothelial cells (ECs) on the surface with a unidirectional wettability gradient. The surface chemical gradient, in which molar fractions of cyclic carbonate and hydroxyl groups were inversely varied, was prepared by continuous immersion of a poly(vinylene carbonate) (PVCa) film into an aqueous solution of sodium hydroxide at a constant speed. Advancing water contact angles of the surface, which ranged from 60° for an untreated PVCa surface to around 20° for a well-treated surface, gradually decreased with the distance from the untreated end of the film. Quantitative analyses of cellular characteristics of adhered cells on the gradient surface, which included the initial adhesion rate and the morphological indices of adhered cells such as spreading area, peripheral length, and circular coefficient, showed that these cells gave the highest values on the untreated PVCa surface and rapidly decreased on the surface regions with shorter periods of hydrolysis, followed by a slower decrease on surface regions with longer periods ofhydrolysis with increasing distance from the untreated end. Little adhesion occurred in a well-hydrolyzed, very hydrophilic surface region. The highest migration rate of adhered cells occurred on the slightly hydrophobic surface region (advancing contact angle, 35°) where adhered cells tended to delaminate as tissue formation proceeded. These results indicate that each cellular potential of ECs is dependent on the wettability of the gradient surface, producing polymorphorous states of adhered cells. Thus, the wettability gradient surface served as an excellent substrate to simultaneously study cellular response dependence on surface chemical composition and wettability.