A two-photon fluorescent probe for basal formaldehyde imaging in zebrafish and visualization of mitochondrial damage induced by FA stress.

The detection of mitochondrial formaldehyde (FA) is of great significance because FA is generated through a one-carbon formaldehyde cycle in mitochondria, and abnormal elevations in FA levels can damage mitochondria by decreasing the mitochondrial membrane potential and inhibiting mitochondrial respiration. Herein, a mitochondria-targetable two-photon probe (Mito-FA-FP) has been well demonstrated. Mito-FA-FP is conjugated with hydrazine as the FA-reactive site and a pyridine derivate as the mitochondria-targetable moiety. After reacting with FA, Mito-FA-FP exhibits dramatic fluorescence enhancement (12-fold) due to suppression of the PET process in the probe and presents good selectivity as well as high sensitivity (LOD: 12.4 μM). Moreover, Mito-FA-FP can be utilized to monitor endogenous FA in mitochondria and evaluate mitochondrial damage caused by FA stress through observing mitochondrial morphology changes. With good two-photon absorption cross-section and high two-photon fluorescence contrast, Mito-FA-FP has been successfully employed for the two-photon fluorescence imaging of basal FA in zebrafish.