Zr-Based Metal-Organic Frameworks-Assisted Ice-Recrystallization Inhibition

The potential applications of antifreeze proteins (AFPs) are of great importance in the biotechnological, pharmaceutical, biochemical or food industries as the purpose of storage of protein drugs, cells, tissues, and food, as well as ice slurries for refrigeration systems. However, it is difficult to use natural AFPs as cryopreservation agents in practical industry because they are irreversibly denatured and difficult to obtain from nature. These challenges have led to the development of artificial cryopreservation agents such as dimethyl sulfoxide and sodium phosphates, but due to their cytotoxicity and lower biocompatibility, the recovery rate of the target substance is too low when they are added. Metal-organic frameworks (MOFs) nanoparticles (NPs) have properties mimicking from those of AFPs and can provide periodically arranged ice-binding sites by modifying organic linkers. In this study, zirconium (Zr) was adopted as a metal cluster that is well dispersed and stable in an eco-friendly water solvent. We investigated the influence of the size of MOF NPs on the antifreeze activity because the microcurvature of the ice surface can be varied by the attachment of MOF NPs during recrystallization. The specific chemical moiety was simply introduced into the acrylate-functionalized MOF NPs to enhance the inhibition of ice recrystallization. This work provides a strategy for the fabrication of low-cost, high-volume antifreeze nanoagents that can extend practical applications to organ transplantation, cord blood storage, and vaccines/drugs.