Dynamic in vitro hemocompatibility testing of poly(ether imide) membranes functionalized with linear,methylated oligoglycerol and oligo(ethylene glycol)

Linear, side-chain methylated oligoglycerols (OGMe) were recently reported as potential surface passivating molecules for improving the protein resistance of cardiovascular application relevant poly(ether imide) (PEI) membranes. A previously reported in vitro screening under static test conditions allowed an end-point evaluation of the adhesion and activation of adherent thrombocytes performed on the material surfaces and revealed similar levels of thrombogenicity on PEI membranes, functionalized with OGMe and oligo(ethylene glycol) (OEG) of similar molecular weight (M_n = 1,300 g·mol⁻¹ - 1,800 g·mol⁻¹). In the present study, we investigated the hemocompatibility of these materials in a dynamic closed loop system, in order to study time-dependent thrombocyte material interactions also of the circulating thrombocytes by mimicking in vivo relevant flow conditions in a dynamic test system with multiple material contacts. Activation and aggregation of circulating thrombocytes as well as complement activation and plasmatic coagulation were evaluated after 40 circulations of thrombocyte rich plasma in the closed loop system. The results of the dynamic tests revealed no differences between the OGMe and OEG functionalized PEI membranes. Furthermore, no differences were observed between the latter and a PEI membrane treated under the conditions of functionalization at pH 11 (PEI-pH11) without an oligoether being present. Blood plasma protein adsorption, as well as activation, and adherence of circulating thrombocytes occurred in a comparable, but minor manner on all investigated PEI membranes. From this we conclude that the OGMe and OEG surface functionalization did not lead to an improvement of the already good hemocompatibility of the PEI-pH11 membrane.