Plunge-Freezing Cryopreservation of Tendons.

Allograft transplantation is an important method for tendon reconstruction after injury, and its clinical success highly relies on the storage and transportation of the grafts. Cryopreservation is a promising strategy for tendon storage. In this study, we report a novel cryopreservation agent (CPA) formulation with a high biocompatibility for tendon cryopreservation. Mainly composed of natural zwitterionic betaine and the biocompatible polymer poly(vinylpyrrolidone) (PVP), it exhibited ideal abilities to depress the freezing point and inhibit ice growth and recrystallization. Notably, after cryopreservation via plunge-freezing for 1 month, Young's modulus (144 MPa, 98% of fresh tendons) and ultimate stress (46.7 MPa, 99% of fresh tendons) remained stable, and the cross-linking of collagen microfibers, protein structures, and glycosaminoglycan (GAG) contents changed slightly. These results indicate that the formulation (5 wt % betaine and 5 wt % PVP in phosphate-buffered saline, PBS solution) effectively maintains the biomechanical properties and tissue structure. This work offers a novel cryopreservation method for tendons and may also provide insights into the long-term preservation of various other tissues.