pH‐Sensitive Capsules as Intracellular Optical Reporters for Monitoring Lysosomal pH Changes Upon Stimulation

TLDR

The study introduces a long‑term lysosomal ion sensor to monitor intracellular pH changes. The sensor is built by layer‑by‑layer assembly of oppositely charged polyelectrolytes around proton‑sensitive fluorophores, is spontaneously internalized, remains in lysosomes for days, and reports real‑time proton concentration changes upon stimulation. Using the sensor, the authors show that Monensin, Chloroquine, Bafilomycin A1, and Amiloride exhibit distinct kinetics and mechanisms in altering lysosomal pH.

Abstract

Abstract The concept of a long‐term sensor for ion changes in the lysosome is presented. The sensor is made by layer‐by‐layer assembly of oppositely charged polyelectrolytes around ion‐sensitive fluorophores, in this case for protons. The sensor is spontaneously incorporated by cells and resides over days in the lysosome. Intracellular changes of the concentration of protons upon cellular stimulation with pH‐active agents are monitored by read‐out of the sensor fluorescence at real time. With help of this sensor concept it is demonstrated that the different agents used (Monensin, Chloroquine, Bafilomycin A1, Amiloride) possessed different kinetics and mechanisms of action in affecting the intracellular pH values.