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

In\nnature, organisms living in extreme environmental conditions\nproduce antifreeze proteins (AFPs) that prevent the growth of ice\ncrystals and depress the freezing point of body fluids. In this study,\nthree different peptides derived from the N-terminal sequence of the\nhelical type I AFP HPLC6, along with a stapled derivative produced\nvia on-resin microwave-assisted copper(I)-catalyzed azide–alkyne\ncycloaddition, were conjugated to gold nanoparticles. The aim of decorating\nthe surface of the nanoparticles with multiple copies of the peptides\nwas to combine the ice-binding capability of the peptides with the\nsize of a nanoparticle, thus, mimicking the protein bulkiness to enhance\nthe peptide antifreeze activity. Ice recrystallization inhibition\nexperiments on the functionalized gold nanoparticles showed a decrease\nin the ice crystal growth rates with the stapled conjugate being the\nmost active. Conformational studies indicated a major helical content\nin the constrained peptide, highlighting the importance of a stable\nconformation for antifreeze activity. Finally, cytotoxicity tests\nshowed that both the peptides and the nanoparticle constructs were\nnontoxic. The proposed approach could thus represent the starting\npoint for developing effective strategies for cryopreservation.