Gold Nanoparticle-Tethered Peptide Nanofibrils for Monitoring Ice Recrystallization Inhibition: Implications for Cryopreservation

Antifreeze proteins (AFPs) that enable polar organisms to survive subzero temperatures are structurally bound to a specific ice surface, regulating crystal formation and growth. To design emerging cryopreservatives that mimic AFPs, it is necessary to understand how the binding intervals corresponding to a particular ice crystal plane and how the amphiphilic nature of AFPs affect the growth of ice crystals. Herein, we report peptide nanoscaffolds containing a glycyl–histidyl–lysine (GHK) tripeptide capable of tethering with gold nanoparticles (Au NPs) that can readily monitor ice recrystallization inhibition (IRI) activity. Representative ice-binding amino acids were introduced into the main scaffold of N-fluorenylmethyloxycarbonyl-diphenylalanine, which forms robust, self-assembled fibrillar nanoaggregates with enhanced colloidal stability due to π–π stacking. This resulted in an enhanced IRI effect. The IRI activity was differentiated depending on the amphiphilicity of the outermost ice-binding pendant of peptide fibrils. This could be confirmed through a colorimetric assay based on the dispersion of Au NPs in peptide fibrils. The adsorbing process to the ice-binding surface could be directly visualized through enhanced scattering caused by Au NPs confined in peptide nanofibrils. The designed peptide supramolecular nanotracker provides a facile strategy to screen antifreeze performance by allowing visualization of how ice growth is prevented. The selected biocompatible peptide nanoagents could further mimic the properties of native AFP through more sophisticated structural controls at the molecular and nanoscale levels and have the potential to be used as cryopreservatives for cord blood, oocytes, sperm, stem cells, tissues, and organs as well as optical labeling nanoprobes for IRI.