Calcium-Induced Morphological Transitions in Peptide Amphiphiles Detected by ¹⁹F-Magnetic Resonance Imaging

Misregulation of extracellular Ca 2+ can indicate bone-related pathologies. New, noninvasive tools are required to image Ca 2+ fluxes and fluorine magnetic resonance imaging ( 19 F-MRI) is uniquely suited to this challenge. Here, we present three, highly fluorinated peptide amphiphiles that self-assemble into nanoribbons in buffered saline and demonstrate these nanostructures can be programmed to change 19 F-NMR signal intensity as a function of Ca 2+ concentration. We determined these nanostructures show significant reduction in 19 F-NMR signal as nanoribbon width increases in response to Ca 2+, corresponding to 19 F-MR image intensity reduction. Thus, these peptide amphiphiles can be used to quantitatively image biologically relevant Ca 2+ concentrations.