A colorimetric and turn-on fluorescent probe for visualization of lysosomal pH fluctuation

Lysosomal pH is important for regulating various physiological processes, and slight fluctuations in lysosomal pH can induce many adverse effects on cellular status, such as inflammation, aging, and tumours. Heat stroke is one of the most serious causes of morbidity and mortality. However, the relationship between heat shock and lysosomal pH values is still poorly understood. Herein, we introduced a colorimetric and turn-on fluorescent probe in the red to NIR range for monitoring lysosomal pH values. The probe can selectively accumulate in lysosomes with a high Pearson's coefficient (0.95), and the suitable pK_a value (6.73 ± 0.07) enables the probe to visualize changes in lysosomal pH values during the stimulation by chloroquine and heat stroke, respectively.