A novel IONP-decorated two-dimensional [Zn2+]:[Insulin] nanosheet with ordered array of surface channels and cellular uptake potential

The study presents the novel design and potential function of a two-dimensional nanosheet formed at the liquid-liquid interface between FeII,IIIoxide nanoparticles (IONPs) and [Zn2+]:[Insulin]. Under thermal stress, the supramolecular organization of [Zn2+]:[Insulin] shifted from hydrophilic phase to hydrophobic, which gradually dissolved with the IONP hydrophobic layer. As a consequence, insulin monomers assembled into two-dimensional nanosheets by intercalating Zn2+-bridges, whereas, the IONPs (18–20 nm) were oxidized from Fe3O4 to Fe2O3 crystals, and decomposed into ultra-small crystallites of 2–5 nm. These tiny crystallites were found adsorbed on the nanosheet surface, creating IONP-decorated insulin nanosheet. To our knowledge, the ability of insulin to form nanosheet-structure has never been reported earlier. Adding to its uniqueness, the IONP-insulin nanosheets formed ordered arrays of superimposed surface wrinkles, giving rise to geometrically arranged channels. These surface properties have been previously demonstrated with graphene, but the ability of proteins to exhibit such material properties has not been reported earlier. Thus, the study demonstrates an entirely new potential of proteins, in this case insulin, and is believed to be a new advancement in protein-based bio-nanomaterials. Further, cellular uptake of these nanosheets was observed when BHK-21 cells were cultured on its layer, thereby displaying cell-targeting potential. [Display omitted]