Interaction of thrombocytes with poly(ether imide): The influence of processing

Abstract

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)...

A novel blood incubation system for the in‐vitro assessment of interactions between platelets and biomaterial surfaces under dynamic flow conditions: The Hemocoater

“…These observations correspond to other studies which showed that hydrophobic and rough surfaces tend to cause more thrombocyte adhesion than hydrophilic and smooth surfaces. [38][39][40][41][42][43][44][45] This confirms that the Hemocoater is an appropriate hemocompatibility testing system regarding adhesion of thrombocytes on different material surfaces.…”

The pathology of the foreign body reaction against biomaterials

“…Surface topography, including general roughness, is another feature that often is associated with an increased protein adsorption, cell adhesion, and differentiation . Besenbacheŕs group reported that nano‐rough surfaces (surface features smaller than 100 nm) change protein conformations .…”

“…In addition, rough and hydrophobic surfaces are prone to the formation of stable gas nucleoli, even in the smallest micropores. Such entrapped air nuclei—not successfully removed from the surface—may also account for thrombogenicity …”

Viability and function of primary human endothelial cells on smooth poly(ether imide) films

“…37 In a comparative study between PEI-membranes and -films, Braune et al showed that platelet adherence can strongly be reduced by the processing of PEI (by changing surface roughness). 6 Therefore, this study was performed to investigate the behavior of HUVEC seeded on smooth PEIfilms (R q = 2.37 ± 1.40 nm). In the framework of the study the cytotoxicity, endothelial cell monolayer formation, cell-substrate as well as cell-cell interaction and the secretion profile of vasoactive as well as inflammatory mediators under in vitro conditions were analyzed to evaluate if this low thrombogenic material is suitable as biomaterial for cardiovascular devices.…”