The anti-calcification potential of a silsesquioxane nanocomposite polymer under in vitro conditions: Potential material for synthetic leaflet heart valve

Calcification currently represents a major cause of failure of biological tissue heart valves. It is a complex phenomenon influenced by a number of biochemical and mechanical factors. Recent advances in material science offer new polymers with improved properties, potentially suitable for synthetic leaflets heart valves manufacturing. In this study, the calcification-resistance efficacy and mechanical and surface properties of a new nanocomposite polymeric material (polyhedral oligomeric silsesquioxane–poly(carbonate-urea)urethane; POSS–PCU) which has been developed by our group are assessed by means of in vitro testing. In particular, thin sheets of nanocomposite, glutaraldehyde-fixed bovine pericardium (BP) and polyurethane (PU) were exposed to a calcium solution into a specially designed in vitro accelerated physiological pulsatile pressure system for a period of 31 days and a total of 4 × 107 cycles. The samples were investigated for signs of calcification after exposure to calcium solution by means of X-ray, microscopic and chemical inspections. Mechanical and surface properties were also studied using stress–strain behaviour and surface morphology and hydrophobicity. Comparison shows that, in the experimental conditions, the level of calcification for the nanocomposite is considerably lower than for the fixed BP (p = 0.008) and PU samples (p = 0.015). Also, mechanical properties were unchanged in POSS–PCU, while there was a significant deterioration in PU samples (p < 0.05). Hydrophobicity was significantly reduced in both the POSS–PCU and PU samples (p < 0.0001). However, the POSS–PCU nanocomposite remained more hydrophobic than the PU sample (p < 0.0001). Less platelet adhered to the POSS–PCU compared to the PU (p < 0.0001). These results indicate that the use of this nanocomposite in synthetic leaflets heart valves may lead to potential advantages in terms of long-term performances and durability.