A Strategy for Specific Fluorescence Imaging of Monoamine OxidaseA in Living Cells

Monoamine oxidase (MAO) has two isoforms, MAO-A and MAO-B, which show different functions, and thus selective fluorescence imaging is important for biological studies. Currently, however, specific detection of MAO-A remains a great challenge. Herein, we report a new strategy for specific imaging of MAO-A through the design of fluorogenic probes combining the characteristic structure of an inhibitor of the target enzyme along with propylamine as a recognition moiety. The high specificity of our representative probe is demonstrated by imaging MAO-A in different live cells such as SH-SY5Y (high levels of MAO-A) and HepG2 (high levels of MAO-B), and further validated by western blot analyses. The superior specificity of the probe may enable the accurate detection of MAO-A in complex biosystems. Importantly, the use of the characteristic structure of an inhibitor, as demonstrated in this work, may serve as a general strategy to design specific recognition moieties for fluorogenic probes for enzymes.