The processing of polymers for blood contacting devices can have a major influence on surface properties. In this study, we fabricated poly(ether imide) (PEI) membranes and films to investigate the effects of the processing on physicochemical surface properties by atomic force microscopy (AFM), scanning electron microscopy, contact angle as well as zeta potential measurements. A static platelet adhesion test was performed to analyze the thrombogenicity of both devices. While contact angle measurements showed similar levels of hydrophobicity and zeta potential values were equivalent, mean surface roughness as well as surface energies in the dispersive part were found to be increased for the PEI membrane. The static platelet adhesion test showed a significantly decreased number of adherent platelets per surface area on the PEI film (178.98 ± 102.70/45000 m 2 ) compared to the PEI membrane (504 ± 314.27/45000 m 2 ) and, consequently, revealed evidence for higher thrombogenicity of the PEI membrane. This study shows that processing can have a significant effect on platelet adhesion to biomaterials, even though, molar weight was identical. Thrombogenicity of polymer-based cardiovascular devices, therefore, have to be evaluated at the final product level, following the entire processing procedure.A wide range of polymers like polyurethanes, silicones or PEG-based copolymers have received growing attention for biomedical applications due to their better hemocompatibility and processing features compared to metals [26], whereupon the ideal hemocompatible surface inhibits any platelet adhesion [20]. Several parameters seem to influence hemocompatibility. Chapman et al. concluded that hydrophilic, noncharged surfaces, without hydrogen-donors are more resistant to protein adsorption and are able to prevent platelet adherence [13]. In addition the processing itself can lead to changes e.g. in surface roughness which can influence platelet adhesion as well [16,17,31,33,42].In the present study the influence of different processing of poly(ether imide) (PEI, Ultem 1000 ® , General Electric, USA) on the interaction of blood platelets with poly(ether imide) (PEI) was analyzed. PEI is non-toxic, sterilizable [1], processable to different formed-bodies [4,5], and enables a wide range of surface modifications by straightforward wet chemistry [2, 3] and was already evaluated as a biomaterial [6,24,32,35,36] suitable for applications in regenerative medicine [30,41].Since platelet interactions are controlled by physical and chemical characteristics [26], including their possible distribution in submicroscopical domains and surface roughness [37], characteristic surface parameters were analyzed. To reveal the influences of processing on surface properties, membranes and films from PEI were fabricated and the effects on the physicochemical properties and thrombogenicity investigated.
Material and methods
Polymer preparationAll processed devices were fabricated from the same charge of the polymer. PEI (Ultem 1000, General Electric, USA)...