Tailoring Peek Crystallinity: Key For Highly Hemocompatible And Mechanically Performing Cardiovascular Implants
Jialu Chen1, Georgios A. Pappas1, Daniele Massella1, Arthur Schlothauer1, Sarah Motta2, Volkmar Falk3, Nikola Cesarovic3, Paolo Ermanni1.
1ETH Zurich, Zurich, Switzerland, 2University of Zurich, Zurich, Switzerland, 3Deutsches Herzzentrum Berlin, Berlin, Germany.
BACKGROUND: Polymeric transcatheter heart valves have the potential to combine the durability of mechanical heart valves with the biocompatibility of biological heart valves, resulting in devices optimized for minimally invasive surgery. However, due to their synthetic origin, polymeric materials still face issues regarding hemocompatibility. This underscores the need for the investigation of methods to improve the hemocompatibility of polymeric materials. In this research, we report on the effect of crystallinity on hemolysis, thrombogenicity, and platelet adhesion in polyetheretherketone (PEEK) surfaces, acknowledging the vast potential of PEEK on cardiovascular device design.
METHODS: To improve properties of implantable cardiovascular devices, the effect of crystallinity on the hemocompatibility of PEEK surfaces is investigated. After annealing at different temperatures, the chemical composition and concentration of different functional groups is determined through Fourier-transform infrared spectroscopy (FTIR) analysis. The resulting change in hemolytic activity, thrombogenicity, and platelet adhesion is observed by standardized hemocompatibility test, alongside changes in mechanical properties such as tensile modulus and toughness.
RESULTS: Higher crystallinity results in increased abundance of oxygen-containing surface functional groups. This increase of negatively charged surface functional groups causes significant reductions in the hemolysis (1.57 to 0.75% cm-2), thrombin generation rate (4840 to 1586 mU mL-1 min-1 cm-2), and platelet adhesion (31.9 to 1.5%). Further, optimized tensile toughness can be accomplished at a moderate crystallinity, with acceptable hemocompatibility indexes.
CONCLUSIONS: Our results show that crystalline PEEK is highly blood compatible in all test categories. Our results also show that this increase in hemocompatibility can be accompanied by an optimization in the tensile modulus and toughness. Hence, crystallization is shown to be a simple and effective method to improve compatibility with blood and mechanical performance of PEEK used for cardiovascular implants.
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