Siloxane-based segmented poly(urethane-urea) elastomers with enhanced mechanical properties, hydrophobicity and anti-calcification based on hierarchical phase separation for potential applications of polymeric heart valve

Abstract

The polymeric heart valves have attracted considerable attention for treating valvular heart diseases with favorable biocompatibility, stability and adjustable mechanical properties. However, the thrombosis, calcification, and mechanical durability in the dynamic blood environment have limited further applications. Polycarbonate (PCDL) and polysiloxane (PDMS) had high flexibility, low toxicity, excellent hydrolytic and oxidative stability and efficient biocompatibility, but PCDL was susceptible to calcification and PDMS was susceptible to protein adsorption. To solve these difficulties, PDMS and PCDL were chosen as soft segments to combine the virtues of excellent biocompatibility, hydrolytic stability, and good anti-calcification and anti-protein adsorption, and a series of PCDL-PDMS poly(urethane-urea) elastomers (PCDL-PDMS PUU) were synthesized using a two-step polymerization reaction based on the amino-terminated polydimethylsiloxane (H2N-PDMS-NH2), polycarbonate diol (PCDL) and isophorone diisocyanate. The thermodynamic incompatibility between PDMS and PCDL and hierarchical hydrogen bonds were used to construct microscopic micro-separation, enabling the combination of enhanced mechanical strength, toughness, tear resistance and biocompatibility. The effect of the molar ratio of PCDL and PDMS and hierarchical H-bonding interactions on the physical properties, biostability and biocompatibility of PCDL-PDMS PUU were investigated. It was found the PCDL-PDMS PUU could achieve relatively stable mechanical strength behavior, and the Young’s modulus and tear strengths increased with the increasing proportion of H2N-PDMS-NH2. Meanwhile, PCDL-PDMS PUU showed low water uptake rate lower than 2 %, very good anti-hydrolysis performance, low hemolysis rate of less than 2 % and low adhesion to platelet cells. What’s more, PCDL-PDMS PUU showed enhanced calcification resistance when compared with a commercial polyurethane, ElastollanTM 1180A. Therefore, the results demonstrated that PCDL-PDMS PUU elastomers showed great potential to be explored as heart valves material considering high biostability, superior biocompatibility and mechanical performances.