A naphthalimide-aminal-based pH-sensitive fluorescent donor for lysosome-targeted formaldehyde release and fluorescence turn-on readout.

A naphthalimide-aminal-based fluorescent donor (NAP-FAD-1) is a pH-sensitive smart donor, which features accelerated FA release at pH 5.0 compared to that at pH 7.4 and fluorescence turn-on readout for facile tracking and quantification of FA release. Confocal imaging studies of HeLa cells co-incubated with Lyso-Tracker Red suggested that its FA release is lysosome-targeted.