Plasma functionalization of polycarbonaturethane to improve endothelialization—Effect of shear stress as a critical factor for biocompatibility control

Abstract

Medical devices made of polycarbonaturethane (PCU) combine excellent mechanical properties and little biological degradation, but restricted hemocompatibility. Modifications of PCU might reduce platelet adhesion and promote stable endothelialization. PCU was modified using gas plasma treatment, binding of hydrogels, and coupling of cellactive molecules (modified heparin, anti-thrombin III (ATIII), argatroban, fibronectin, laminin-nonapeptide, peptides with integrin-binding arginine-glycine-aspartic acid (RGD) motif). Biocompatibility was verified with static and dynamic cell culture techniques. Blinded analysis focused on improvement in endothelial cell (EC) adhesion/proliferation, antithrombogenicity, reproducible manufacturing process, and shear stress tolerance of ECs. EC adhesion and antithrombogenicity were achieved with 9/35 modifications. Additionally, 6/9 stimulated EC proliferation and 3/6 modification processes were highly reproducible for endothelialization. The latter modifications comprised immobilization of ATIII (A), polyethyleneglycole-diamine-hydrogel (E) and polyethylenimine-hydrogel connected with modified heparin (IH). Under sheer stress, only the IH modification improved EC adhesion within the graft. However, ECs did not arrange in flow direction and cell anchorage was restricted. Despite large variation in surface modification chemistry and improved EC adhesion under static culture conditions, additional introduction of shear stress foiled promising preliminary data. Therefore, biocompatibility testing required not only static tests but also usage of physiological conditions such as shear stress in the case of vascular grafts.

Effect of Immobilized Antithrombin III on the Thromboresistance of Polycarbonate Urethane

“…Chemical modifications have been used to improve the hemocompatibility of Chronoflex AR as a potential material for the pump chamber of implantable VAD systems [20]. Among the modified PCU samples used in the present study, PEI-AT modification had minor effects on mechanical properties and showed increased wettability, reduced bacterial cell binding, suppressed platelet adhesion and activation, and activation of complement and coagulation under shear stress.…”

“…The details on handling and modifying the PCU discs and helical grafts have been described previously [20]. Chemicals were obtained from Merck (Darmstadt, Germany) or Sigma-Aldrich (Munich, Germany), unless noted otherwise.…”

“…In a previous study, a static platelet adhesion test was used to discriminate the platelet adhesion of different surface modifications, including all intermediate modified PCU materials [20]. In brief, plasma-activation did not improve hemocompatibility.…”

“…10-101-0159). Platelet-rich plasma (PRP) was isolated as described earlier [20]. For platelet adhesion testing, PRP (50 µL; 5 × 10 7 platelets per 0.3 cm 2 ) was coincubated with the PCU samples (37 °C, 5% CO 2 , 30 min), washed with PBS and processed as described in Section 2.7.…”

“…In a previous study we showed that covalent binding of AT improved anti-thrombotic properties of untreated PCU, independent of the type of connecting hydrogel [20]. However, reproducible low platelet adhesion was only documented for the combination of PEG-DEX and PEI with AT [20]. Therefore, these modifications were analyzed to verify their antithrombotic functionality under physiological conditions, such as shear stress.…”