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BACKGROUND: Native antifreeze proteins (AFPs) have been discovered in various extremophile organisms, where they are produced to enable survival in freezing temperatures by modulating ice formation and growth. The Kramer Lab has taken inspiration from native AFPs to produce synthetic polymers with ice-modulating activity, which have potential applications in industrial, food, and biomedical industries, in particular cellular cryopreservation. Importantly, the synthetic polymer's ice recrystallization inhibition (IRI) activity, which prevents the formation of larger and more damaging ice crystals, has vast implications in improving the freeze/thaw damage of biological samples that can occur during cryopreservation. OBJECTIVE: N-carboxyanhydride (NCA) polymerization is used to produce high molecular weight (MW)-polymers with a native peptide backbone, synthesized from commercially available amino acids. We aim to subsequently characterize the IRI activity of our synthetic mimics. Notably, the MW of native AFPs have been found to correlate with antifreeze activity, therefore, we expect synthetic AFPs with an increased polymeric length will exhibit higher IRI activity. METHODS: IRI activity is quantified using a "splat" assay which demonstrates the ability of our polymers to mitigate ice crystal formation. Circular Dichroism (CD) spectroscopy is used to determine the secondary structure of our polymers and their heat stability. RESULTS: All synthetic AFPs regardless of length exhibited significant IRI activity compared to our 1X PBS control, and all had an alpha-helical structure. Our most IRI active polymer was our 25MI polymer, which at 1mg/mL resulted in over a 99% decrease in ice crystal mean grain size (MGS), and remained highly active even at extremely low temperatures. CONCLUSION: This work signals the efficacy of our synthetic mimics in significantly reducing ice crystal size and suggests that the IRI activity of our polymers is length dependent. More work is necessary to determine whether this IRI activity correlates to improved cryopreservation outcomes.