Rational Design of Oxazolidine-Based Red Fluorescent pH Probe for Simultaneous Imaging Two Subcellular Organelles

A reversible pH-responsive fluorescent probe, BP, was rationally designed and synthesized, based on protonation and deprotonation gave rise to oxazolidine ring open and close. The fluorescence response of BP against pH ranges from 3.78 to 7.54, which is suitable for labeling intracellular pH-dependent organelles. BP displayed strong red emission at a relatively high pH in living HeLa cells and U87 cells. More importantly, this probe exhibited good colocalization with both mitochondria and lysosomes in these two cell lines, attributing to pH-induced structure tautomerism resulting in an oxazolidine ring open and close that triggered effective targeting of these two organelles. As organelle interactions are critical for cellular processes, this strategy of targeting dual organelles through the structure tautomerism is conducive to further developing more effective and advanced probes for real-time imaging of the interaction between mitochondria and lysosomes.