pH-Triggered mitochondria targeting fluorescent probe for detecting Monoamine Oxidases A in living cells

Monoamine oxidase A (MAO-A) is involved in various diseases such as heart failure (HF), prostate cancer (PCa), psychiatric disorders, etc. The precise sensing of MAO-A is important to elucidate its function in various biological processes, as well the diagnosis and treatment of related diseases. In this research, we created a brandnew fluorescence probe ANET for the specific detection of MAO-A. Propylamine moiety of ANET was specifically recognized for MAO-A and then the product EHBT was released. A well-calculated pKa value of 8.01 & PLUSMN; 0.02 was achieved for EHBT by pH-dependent spectra. The fluorescence at 700 nm of EHBT was observed at pH 8.0 due to the enhanced intramolecular charge transfer (ICT). The fluorescence intensity of EHBT at 559/700 nm was in a linear relationship with MAO-A concentration in the 0.375-1.50 & mu;g/mL range. The detection limit was 19.8 ng/mL. It is well known that the environment of mitochondria is microalkaline (pH 8.0), however, other organelles are neutral or acidic. So the fluorescence at 700 nm of ANET could be notably turned on by MAO-A in mitochondria. In addition, ANET can selectively accumulate in the mitochondria through powerful electrostatic attractions. Finally, ANET was applied for specific imaging of MAO-A in mitochondria of SH-SY5Y, PC-3, and glucose-deprived (GD) H9c2 cells.