Dual Hydrazine-Equipped Turn-On Manganese-Based Probes for Magnetic Resonance Imaging of Liver Fibrogenesis

Liver fibrogenesis is accompanied by upregulation of lysyl oxidase enzymes, which catalyze oxidation of lysine ε-amino groups on the extracellular matrix proteins to form the aldehyde containing amino acid allysine (Lys^Ald). Here, we describe the design and synthesis of novel manganese-based MRI probes with high signal amplification for imaging liver fibrogenesis. Rational design of a series of stable hydrazine-equipped manganese MRI probes gives Mn-2CHyd with the highest affinity and turn-on relaxivity (4-fold) upon reaction with Lys^Ald. A dynamic PET-MRI study using [⁵²Mn]Mn-2CHyd showed low liver uptake of the probe in healthy mice. The ability of the probe to detect liver fibrogenesis was then demonstrated in vivo in CCl₄-injured mice. This study enables further development and application of manganese-based hydrazine-equipped probes for imaging liver fibrogenesis.