Synthesis and characterization of a redox- and light-sensitive MRI contrast agent

A redox- and light-sensitive, T1-weighted magnetic resonance imaging (MRI) contrast agent, which tethers a spiropyran (SP)/merocyanine (MC) motif to a Gd–DO3A moiety was synthesized and characterized. When in the dark, the probe is in its MC form, which has an r1 relaxivity of 2.51 m M−1 s−1 (60 MHz, 37 °C). After irradiation with visible light or mixing with NADH, the probe experiences an isomerization and the r1 relaxivity decreased 18% and 26%, respectively. Additionally, the signal intensity in MRI showed an observable decrease after the compound was mixed with NADH.