Effects of segment chemistry on mechanical performance and hemocompatibility in polyurethane heart valve scaffolds

Polycarbonate-based and polysiloxane-modified thermoplastic polyurethanes (TPUs) are promising candidates for cardiovascular implants because of their tunable mechanical properties and favorable biocompatibility. In this study, we established comparative formulation-property-hemocompatibility criteria for polymeric heart valve scaffolds through a systematic evaluation of five commercial TPU formulations: carbothane AC-4095A (CB95-AC), carbothane AC-4075A (CB75-AC), carbothane PC-3575A (CB75-PC), chronoflex C65D (CF), and quadrasil ARCS 90A (Qsil). This comparative analysis provides practical material-selection criteria based on the balance between elastic recovery, tear resistance, oxidative stability, and hemocompatibility. CF and CB95-AC exhibited the highest stiffness and tensile strength, whereas CB75-AC and CB75-PC demonstrated greater elasticity and lower residual strain during cyclic loading. CB75-AC exhibited the lowest hysteresis and best elastic recovery; however, it also exhibited low tear resistance and slightly elevated hemolysis (∼4%), highlighting the tradeoff between elastic recovery and mechanical robustness. All TPU materials maintained platelet counts and partial thromboplastin time values within ASTM-defined acceptable ranges. FTIR analysis revealed formulation-dependent differences in urethane carbonyl hydrogen bonding and hard-domain association that were associated with differences in mechanical behavior and surface characteristics. DSC revealed formulation-dependent differences in thermal transitions, whereas WAXD showed broadly similar, predominantly amorphous structures with diffuse scattering centered at approximately 20-21° 2θ and no distinct crystalline reflections. Preliminary short-term implantation of a CB95-AC polymeric mitral valve in an ovine model showed no gross thrombotic attachment on the leaflet surfaces after 22 days. Overall, the results demonstrate formulation-dependent tradeoffs among elastic recovery, tear resistance, oxidative stability, and hemocompatibility in TPU-based heart valve scaffolds. These findings provide practical material-selection criteria for future polymeric heart valve scaffold development.