A red-emissive D-A-D type fluorescent probe for lysosomal pH imaging

摘要

Visual detection of pH changes in lysosomes is critical because lysosomes not only play an important role in diverse cellular functions but also are closely related to various physiological and pathological processes. Herein, we disclose a donor-acceptor-donor (D-A-D) type fluorescent probeDBTDfor detecting pH fluctuation in lysosomes.DBTDwas rationally designed by using benzothiadiazole as the electron acceptor andN,N-diethylamino groups as the electron donor. Owing to its unique D-A-D structure,DBTDdisplayed a red-emission centered at 614 nm. It showed a sensitive and a linear response to pH from 4.5 to 5.2 with a pK(a)of 5.0, which is very suitable for lysosomal pH imaging. The response was based on the intramolecular charge transfer (ICT) effect owing to the protonation of the diethylamino group. Furthermore,DBTDcould accurately monitor lysosomal pH variations in SGC-7901 cells. More importantly, it was able to image the pH change in lysosomes during the autophagy process successfully, suggesting the great potential ofDBTDacting as a powerful tool for monitoring lysosomal pH-related biological processes.