Apatite nanoparticles mediate intracellular delivery of trehalose and increase survival of cryopreserved cells

Cryopreservation of tissue cells is an important method to maintain cell viability and cellular function. However, cell viability and function are less than ideal by conventional cell cryopreservation methods, which may result in apoptosis and necrosis of cells in cryopreservation. Trehalose plays a role in maintaining cell structure and protecting cells from stress. However, owing to the difficulty in transport of trehalose across the cell membrane, its antifreeze effect is limited. A large amount of trehalose (up to 237 ± 8.5 mM) can be delivered to smooth muscle cells incubated in a medium containing trehalose and apatite nanomaterials at 37 °C for 6 h. Our data showed that trehalose was efficiently delivered intracellularly with the aid of nanoparticles (NP), with a loading efficiency up to 137.3 ± 34.5%, thus allowing for cryopreservation of LMC with nontoxic sugar as the sole cryoprotectant. Colloidal bioelastic apatite NP were used as bioactive promoters for the cryopreservation of tissue cells with trehalose. The addition of apatite NP in the medium substantially increased aortic smooth muscle cell cryosurvival, up to 83.6% (30% improvement over control without NP), a level comparable to that associated with the traditional Me₂SO cryoprotective regimen. Furthermore, the cytotoxicity of nanocapsules in the intracellular delivery of trehalose was negligible. This method provides a new option to enhance the activity of valvular cells for cryopreservation.