Bioinspired Structure with Hierarchical Hydrogen Bonding and Metal Coordination for Enhanced Properties of Biobased Polyurethane Applied in Artificial Ligaments

The utilization of biobased polyurethanes in medical engineering is constrained by their inferior mechanical properties. A variety of strategies that aim to improve the mechanical properties of these materials have been developed to meet the specific requirements of biomedical applications. Inspired by the chemical structure of the jawbone of a marine worm called Nereis, the polymer chain can be coordinated with zinc ions to improve biobased polyurethane mechanical properties. In this study, a series of biobased polyurethanes were synthesized via a prepolymerization process involving the usage of biobased polycarbonate diol in conjunction with lysine diisocyanate and isophorone diisocyanate, followed by the addition of isophorone diamine and 2-amino-5-(2-hydroxyethyl)-6-methylpyrimidin-4-ol to complete the chain expansion along with the addition of Zn2+ for coordination. The mechanical properties (including tensile, cycling, and fatigue resistance) and biocompatibility of the biobased polyurethanes were evaluated through a series of tests. The resulting biobased polyurethane, comprising a bioinspired syngeneic structure, exhibited remarkable properties, including a tensile strength of 40.6 MPa, a toughness of 147.6 MPa/m3, and an energy recovery of 91.6%, which represents a 167% improvement in toughness compared to the biobased polyurethane without metal coordination. Furthermore, the biobased polyurethane with the syngenetic effect of hierarchical hydrogen bonding and metal coordination retains 80.2% of its strength after 300 cycles without any crack propagation. In addition, the good biocompatibility of biobased polyurethanes indicates the possibility of in vivo bioapplication, so they should have potential application in artificial ligaments.