Red blood cell-activated antifreeze metal-organic framework armor for cryopreservation

Red blood cell (RBC) cryopreservation is essential for maintaining ex vivo biological function and enabling long-term storage. However, the fragile nature of RBCs makes them highly susceptible to hemolysis during freezing and thaw cycles, limiting their widespread application. Here, a metal-organic framework (MOF)-based armor has been developed in a physiological environment, which enables one-step in situ encapsulation and unloading of RBCs. This MOF armor, functioning as a nano-bio interface, effectively shields RBCs from cryo-induced damage while preserving their native oxygen-carrying function. The MOF-armored RBCs not only inhibit ice recrystallization by restricting water molecule movement within the porous MOF structure but also serve as a "catalyst" to induce the smoothing of the ice front during growth, reducing sodium chloride eutectic formation and accelerating ice melting. Cryopreservation assays demonstrate exceptional RBC recovery (51 %) at a low MOF concentration (1 mg mL^-1), confirming the effectiveness of this protective strategy in enhancing cryoprotectant efficacy. These findings highlight the potential of MOF-derived architectures for the cryopreservation of various cell types and tissue samples, paving the way for innovative preservation technologies.