Ratiometric Near-Infrared Fluorescent Probe for Synergistic Detection of Monoamine Oxidase B and Its Contribution to Oxidative Stress in Cell and Mice Aging Models

As new biomarkers, monoamine oxidases (MAOs) play important roles in maintaining the homeostasis of biogenic amines via catalyzing the oxidation of biogenic amines to corresponding aldehydes with the generation of reactive oxygen species (ROS). MAOs have two isoforms, MAO-A and MAO-B. MAO-A is considered to be a major factor of neuropsychiatric and depressive disorders. However, MAO-B is thought to be involved in several neurodegenerative diseases. Therefore, to explore their distinct roles in different diseases, the selective detection of MAOs is essential. Herein, two new types of near-infrared (NIR) fluorescent probes, MitoCy-NH₂ and MitoHCy-NH₂, are provided for synergistic imaging of MAO-B and its contribution to oxidative stress in cells and in mice aging models. These probes are composed of three moieties: heptamethine cyanine as fluorophore, propanamide as recognition group, and triphenylphosphonium cation as mitochondrial targeting group. The amine oxidation and β-elimination reaction can lead to obvious fluorescence increase and color changes from green to blue. The probe MitoHCy-NH₂ can be used to synergistically detect MAO-B and its contribution to oxidative stress in the replicative senescence model. And the probe MitoCy-NH₂ can offer ratiometric near-infrared fluorescence for the selective detection of MAO-B in the H₂O₂-induced cell aging model and in mice aging models. The results reveal that there are different MAO-B levels in different ages of mice models. MitoCy-NH₂ also can evaluate therapeutic effects of pargyline and selegiline in mice models. The desirable analytical behaviors of our probes make them useful chemical tools for the selective detection of MAO-B and its contribution to oxidative stress in biosystems.