Gold Nanoparticles Decorated with HPLC6-Derived Peptides as a Platform for Ice Recrystallization Inhibition

In nature, organisms living in extreme environmental conditions produce antifreeze proteins (AFPs) that prevent the growth of ice crystals and depress the freezing point of body fluids. In this study, three different peptides derived from the N-terminal sequence of the helical type I AFP HPLC6, along with a stapled derivative produced via on-resin microwave-assisted copper(I)-catalyzed azide-alkyne cycloaddition, were conjugated to gold nanoparticles. The aim of decorating the surface of the nanoparticles with multiple copies of the peptides was to combine the ice-binding capability of the peptides with the size of a nanoparticle, thus, mimicking the protein bulkiness to enhance the peptide antifreeze activity. Ice recrystallization inhibition experiments on the functionalized gold nanoparticles showed a decrease in the ice crystal growth rates with the stapled conjugate being the most active. Conformational studies indicated a major helical content in the constrained peptide, highlighting the importance of a stable conformation for antifreeze activity. Finally, cytotoxicity tests showed that both the peptides and the nanoparticle constructs were nontoxic. The proposed approach could thus represent the starting point for developing effective strategies for cryopreservation.