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

Misregulation of extracellular Ca2+ can indicate bone-related pathologies. New, noninvasive tools are required to image Ca2+ fluxes and fluorine magnetic resonance imaging (19F-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 19F-NMR signal intensity as a function of Ca2+ concentration. We determined these nanostructures show significant reduction in 19F-NMR signal as nanoribbon width increases in response to Ca2+, corresponding to 19F-MR image intensity reduction. Thus, these peptide amphiphiles can be used to quantitatively image biologically relevant Ca2+ concentrations.