Janus Nanohybrids Enable Superflash Warming and High-Affinity Ice Confinement for Cross-Scale Cryopreservation

Strong hydration of cryoprotective agents reduces the glass transition temperature of water and suppresses ice formation. However, lethal cooling and warming remain a critical obstacle to cross-scale cryopreservation of clinical biospecimens. Herein, a snowman-like Janus nanohybrid composed of magnetic iron tetraoxide and photothermal polypyrrole is reported. Its cranial-corporal asymmetry enables heterogeneous hydration for a record high efficiency of ice confinement, reducing mean ice crystal area by 98.4%. Molecular dynamics simulations reveal that Janus architecture simultaneously enhances interactions with ice and strengthens the local hydration anisotropy, accounting for the effective inhibition of ice growth. Superflash warming over 920 °C min^‒1 by magnetically rotating its anisotropic structure for uniform heat dissipation narrows the hostile temperature window in micro-/macroscopic scenarios, as further confirmed by Monte Carlo modeling. This design enables cost-effective post-thaw magnetic retrieval, eliminating the need for heavy centrifuges, well-suited for scalable and on-site applications. As a result, cryopreserved samples from single cells, bacteria, to porcine trachea retain near-complete viability and functionality. Therefore, this study offers a promising technique to bridge the gap between microscale cell storage and whole-organ preservation.