Imaging of lysosomal activity using naphthalimide-benzimidazole based fluorescent probe in living cells

A lysosomal targeting naphthalimide-benzimidazole based probe has been designed, synthesized and evaluated for detecting lysosomal pH changes inside living cells. The probe displays highly selective and sensitive response towards pH changes in aqueous medium. The sensing mechanism involves intramolecular charge transfer from benzimidazole moiety to naphthalimide core. The portable kits were also designed to demonstrate real time application of the probe. Probe 2 was successfully applied to cells and nematodes and all the findings emphasized that it can easily detect the lysosomal pH changes in living cells. To emphasize the ability of probe 2 for determining the lysosomal alkalinisation, a cell based model study was performed using lysomotropic regent chloroquine, results of which demonstrated that probe 2 has the potential for monitoring dynamic pH changes in living systems.