Protein adsorption on gradient surfaces on polyethylene prepared in a shielded gas plasma

In this study, a new and simple method is described to prepare wettability gradients on polymers by means of glow discharge in a partly shielded argon plasma. The surface characteristics of thus prepared gradients on low density polyethylene were determined by contact angle measurements and electron spectroscopy for chemical analysis (ESCA) and demonstrate that a chemical gradient of oxidized groups extends over a length of up to 4.5 cm, depending on the height of the plasma cover and the duration of the treatment. The chemical functionalities in which the oxygen was involved, however, were the same over the length of all gradients. Advancing water contact angles decrease from around 100 degrees on the hydrophobic end to 40 degrees on the hydrophilic end, with a contact angle hysteresis of around 40 degrees. The steepest gradient was obtained with the cover at smaller distance above the polyethylene. Adsorption of albumin, fibrinogen and immunoglobulin G along the length of such a gradient surfaces increased with the distance from the hydrophobic end. (C) 1999 Elsevier Science B.V. All rights reserved.