Ratiometric pH-Responsive F-19 Magnetic Resonance Imaging Contrast Agents Based on Hydrazone Switches

Abstract

Hydrazone-based molecular switches serve as eflicient ratiometric pH-sensitive agents that can be tracked with F-19 NMR/MRI and H-1 NMR. Structural changes induced between pH 3 and 4 lead to signal appearance and disappearance at H-1 and F-19 NMR spectra allowing ratiometric pH measurements. The most pronounced are resonances of the CF3 group shifted by 1.8 ppm with F-19 NMR and a hydrazone proton shifted by 2 ppm with H-1 NMR.Hydrazone-based molecular switches serve as eflicient ratiometric pH-sensitive agents that can be tracked with F-19 NMR/MRI and H-1 NMR. Structural changes induced between pH 3 and 4 lead to signal appearance and disappearance at H-1 and F-19 NMR spectra allowing ratiometric pH measurements. The most pronounced are resonances of the CF3 group shifted by 1.8 ppm with F-19 NMR and a hydrazone proton shifted by 2 ppm with H-1 NMR.