A NIR fluorescent probe for dual imaging of mitochondrial viscosity and FA in living cells and zebrafish

Formaldehyde (FA) and viscosity play multiple roles in human health and diseases, and viscosity has great regional differences due to the diversity of subcellular organelles. However, it is challenging to achieve dual detection of viscosity and FA in subcellular organelles. Herein, we developed a near infrared (NIR) fluorescent probe FA-Cy, which can simultaneously monitor the viscosity and FA concentration of mitochondria in living cells. The probe could detect mitochondrial viscosity and exogenous and endogenous FA in living cells and zebrafish. After the probe recognizes formaldehyde, the fluorescence quenching group leaves, exposing the Cy-7 fluorophore. Meanwhile, the probe contains a near-infrared fluorescent backbone with viscosity response, which can detect viscosity changes.