Selective imaging of cancer cells with a pH-activatable lysosome-targeting fluorescent probe

•The fluorescent probe NBOH showed superior performance for pH detection in a wide pH range with relatively long emission wavelength.•This probe exhibited strong anti-interference ability, photostability and remarkable reversibility.•Flow cytometry study was carried out showing quantitatively that fluorescence intensity of probe NBOH in cancer cells is nearly tenfold of it in normal cells.•Fluorescence imaging of nude mouse indicated the probe can distinguish tumor tissue out of normal tissue in vivo.•The probe exhibited potential application in cancer removal surgery.

Fluorescence imaging with tumor-specific fluorescent probe has emerged as a tool to aid surgeons in the identification and removal of tumor tissue. We report here a new lysosome-targeting fluorescent probe (NBOH) with BODIPY fluorephore to distinguish tumor tissue out of normal tissue based on different pH environment. The probe exhibited remarkable pH-dependent fluorescence behavior in a wide pH range from 3.0 to 11.0, especially a sensitive pH-dependent fluorescence change at pH range between 3.5 and 5.5, corresponding well to the acidic microenvironment of tumor cells, in aqueous solution. The response time of NBOH was extremely short and the photostability was proved to be good. Toxicity test and fluorescence cell imaging together with a sub-cellular localization study were carried out revealing its low biotoxicity and good cell membrane permeability. And NBOH was successfully applied to the imaging of tumor tissue in tumor-bearing mice suggesting potential application to surgery as a tumor-specific probe.

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