3D-printed high-stiffness and antiswelling Diels-Alder crosslinked polycarbonate-based polyurethane for meniscal substitution

The development of a meniscal substitute that conforms to the stringent requirements of high modulus, antiswelling, and shape compatibility continues to pose a significant challenge. Herein, the polycarbonate-based polyurethane (PCU) with a covalent adaptive network is constructed by introducing the Diels-Alder (DA) bonds into the hard segments of PCU as the dynamic covalent cross-linkage. On the one hand, the stability of DA bonds at low temperatures enables them to lock molecular chains within the hard domain in an aqueous environment, thus maintaining the high robustness of the resultant elastomer under physiological conditions. On the other hand, the incorporated DA bonds can be disrupted at high temperatures, facilitating the movement of the molecular chains through heating, thus allowing for the three-dimensional (3D) printing of the meniscus scaffold whose shape closely resembles that of the native tissue. The fabricated meniscus substitute is surgically implanted into the knee joints of rabbits for 12 weeks, with in-vivo outcomes illustratively showcasing its remarkable proficiency in mitigating cartilage surface degradation.