A ratiometric pH probe for unveiling lysosome–lipid droplet interactions and differentiating cancer cells

Abstract

Lysosomal pH plays a crucial role in cellular homeostasis, particularly during autophagy and apoptosis. Thus, using pH probes to study lysosomal pH changes has become an important method. We successfully developed and synthesized a novel pH probe (Fn-pH) utilizing the ICT mechanism and monitored ratiometric fluorescence responses to pH changes. The Fn-pH probe contains a morpholine group that effectively targets lysosomes and relocates to lipid droplets when the lysosomal pH abnormally increases. Using the probe, we successfully observed lysosomal pH increases induced by chloroquine (CQ) and apoptosis, as well as pH decreases during starvation-induced autophagy. Furthermore, we distinguished healthy cells from cancer cells by leveraging their lysosomal pH differences. The Fn-pH probe exhibits large Stokes shifts, excellent photostability, and low cytotoxicity, making it a powerful tool for studying lysosomal pH changes. We believe this probe will provide valuable insights into lysosomal function research.