Poly(vinyl alcohol) (PVA)/dextran hydrogels for heart valve fabrication [English translation]

Around the world, approximately 250,000 people undergo heart valve replacement surgery each year. In Canada, it is estimated that by 2040, nearly 1.5 million people aged over 65 years will have a heart condition associated with valve failure. Current replacements are made with two types of artificial valves: mechanical and bioprosthetic valves. These valves have limitations in terms of biocompatibility, durability, and accessibility. These limits have led to the emergence of polymeric valves, which can be custom-made, their composition being adjustable to optimize their biocompatibility and mechanical properties. However, they also encounter limits regarding their long-term durability and insufficient biocompatibility favoring thrombosis. The main objective of this project is to develop PVA/dextran hydrogels for the manufacture of molded heart valves that exhibit improved biocompatibility while maintaining mechanical properties required for application to heart valves. PVA/dextran hydrogels with increasing dextran concentrations were produced and physically and/or chemically cross-linked (with STMP). These hydrogels were cast in 3D printed heart valve molds. The leakage and dimensional stability of the valves were evaluated. The mechanical properties, cytotoxicity and low-fouling properties of the hydrogels were determined. The valves produced exhibit no leakage and their sizes stabilize two weeks after fabrication. The hydrogels have mechanical properties compatible with the application to heart valves, their Young’s modulus varying from 322 ± 46 kPa to 528 ± 33 kPa and the maximum stresses supported being of the order of 1 MPa. Hydrogels containing the highest concentration of dextran as well as those that have been chemically and physically cross-linked exhibit increased fatigue resistance compared to others. None of the hydrogels shows cytotoxicity. Hydrogels with the highest dextran concentrations exhibit lower fibrinogen adsorption than others, indicating a better ability to reduce thrombogenicity. These results designate the hydrogels PVA/dextran at 100/20 ratio and PVA/dextran/STMP at 100/10/13 ratio as the most promising materials for application to heart valves. In the future, long-term fatigue tests and additional platelet adhesion testing will be required to confirm initial results.