A cobalt(<scp>iii</scp>) complex as a dual-mode probe for the detection of sodium dithionite <i>via</i> MRI and fluorescence

A fluorescence/magnetic resonance (MR) dual-mode molecular probe H1 based on cobalt(III) complexes was designed and synthesized in this work for the detection of sodium dithionite (Na₂S₂O₄) and real-time biological imaging <i>in vivo</i>. The probe combines highly sensitive fluorescence imaging technology and high-resolution magnetic resonance imaging (MRI) technology to address the limitations of each individual modality. Probe H1 used Co³⁺ as the MRI unit and 3-acetylacetone-7-diethylamino-coumarin as the fluorescence unit. The diamagnetic Co³⁺ is reduced to paramagnetic Co²⁺ through the strong reductivity of Na₂S₂O₄, and the MR signal and the fluorescence signal can be activated simultaneously due to the change in magnetic properties of the cobalt ion and the paramagnetic quenching effect of Co²⁺. Probe H1 demonstrates excellent detection performance in monitoring Na₂S₂O₄, including excellent selectivity, high sensitivity (LOD = 9 μM), and anti-interference. Furthermore, probe H1 was successfully applied to the detection of exogenous Na₂S₂O₄<i>in vivo</i> through magnetic resonance/fluorescence dual-mode imaging, which can potentially be used in the pathological hypoxic microenvironment field in the future.