Cryopreservation of tissues and organs can bring transformative changes to medicine and medical science. In the past decades, limited progress has been achieved, although cryopreservation of tissues and organs has long been intensively pursued. One key reason is that the cryoprotective agents (CPAs) currently used for cell cryopreservation cannot effectively preserve tissues and organs because of their cytotoxicity and tissue destructive effect as well as the low efficiency in controlling ice formation. In stark contrast, nature has its unique ways of controlling ice formation, and many living organisms can effectively prevent freezing damage. Ice-binding proteins (IBPs) are regarded as the essential materials identified in these living organisms for regulating ice nucleation and growth. Note that controversial results have been reported on the utilization of IBPs and their mimics for the cryopreservation of tissues and organs, that is, some groups revealed that IBPs and mimics exhibited unique superiorities in tissues cryopreservation, while other groups showed detrimental effects. In this perspective, we analyze possible reasons for the controversy and predict future research directions in the design and construction of IBP inspired ice-binding materials to be used as new CPAs for tissue cryopreservation after briefly introducing the cryo-injuries and the challenges of conventional CPAs in the cryopreservation of tissues and organs.

Antifreeze (glyco)­proteins (AF­(G)­Ps) are naturally evolved ice inhibitors incomparable to any man-made materials, thus, they are gaining intensive interest for cryopreservation and beyond. AF­(G)­Ps depress the freezing temperature (T f) noncolligatively below the melting temperature (T m), generating a thermal hysteresis (TH) gap, within which the ice growth is arrested. However, the ice crystals have been reported to undergo a retaliatory and explosive growth beyond the TH gap, which is lethal to living organisms. Although intensive research has been carried to inhibit such an explosive ice growth, no satisfactory strategy has been discovered until now. Here, we report that crowded solutions mimicking an extracellular matrix (ECM), in which AF­(G)­Ps are located, can completely inhibit the explosive ice growth. The crowded solutions are the condensates of liquid–liquid phase separation consisting of polyethylene glycol (PEG) and sodium citrate (SC), which possess a nanoscale network and strong hydrogen bond (HB) forming ability, completely different to crowded solutions made of single components, that is, PEG or SC. Due to these unique features, the dynamics of the water is significantly slowed down, and the energy needed for breaking the HB between water molecules is distinctly increased; consequently, ice growth is inhibited as the rate of water molecules joining the ice is substantially reduced. The present work not only opens a new avenue for cryopreservation, but also suggests that the ECM of cold-hardy organisms, which also exhibit great water confining properties, may have a positive effect in protecting the living organisms from freezing damage.