Ice-free vitrification and nanowarming of large osteochondral grafts for transplantation

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Resurfacing of articular cartilage with cold stored osteochondral allografts is employed clinically for repair of trauma and osteoarthritis-induced articular cartilage surface damage. Chondrocyte viability of transplanted articular cartilage is accepted as one of the determinants of outcome following osteochondral allograft transplantation. We have previously developed an ice-free vitrification method of cryopreservation that maintains excellent chondrocyte viability in animal model and human articular cartilage. The chondrocytes survive vitrification due to the absence of ice formation during cooling and warming of 1-3mL samples. However, it had not been possible to rewarm larger samples due to ice nucleation during rewarming that results in loss of chondrocyte viability prior to our Phase I studies. The innovation in this proposal relates to a new rewarming method that does not have the limitations of boundary convection warming that should be effective for samples up to 50mL in volume. This rewarming method utilizes radio frequency induced heating of magnetic iron nanoparticles. In Phase I we demonstrated the effectiveness of ice-free vitrification combined with nanowarming for large full thickness osteochondral tissues in 50 mL volumes in 80 seconds with maintenance of both chondrocyte viability and extracellular matrix integrity. In Phase II we propose development of a porcine model, further optimization of ice-free vitrification and nanowarming and in vivo evaluation in a porcine model in three specific aims. Nanowarmed chondrocyte viability, chemistry, and biomaterial properties will be compared with untreated fresh control tissues both before and after transplant. The nanowarming conditions that provides the best preservation of chondrocytes with minimal if any cartilage biomaterial changes will be selected for further investigation and translation to human cartilage in a subsequent Phase IIb SBIR application.