Benzoindole-based bifunctional ratiometric turn-on sensor with an ICT effect for trapping of H and Al in dual-channel cell imaging and samples.

Abnormal changes in H and Al concentrations in living cells can alter neurological diseases. A small-molecule sensor combined with a fluorescence imaging technique holds great promise for monitoring changes in proton and metal-ion concentration. In this work, a bifunctional ratiometric naked-eye fluorescence sensor (BIBC) was developed for turn-on detection of H and Al in HO/EtOH (v/v = 1:1) mixtures. BIBC exhibits a pK value of 4.58 within a linear pH variation from 4.1 to 4.7 (R = 0.9939). Moreover, the fluorescence intensity ratio (I/I) shows a good linear relationship (R = 0.9965) within an Al concentration range of 7.0-10.0 μM. The detection limit (DL) for the sensor was calculated to be 1.58 μM. The practical application of BIBC for Al detection in real samples was further discussed, and satisfactory results were obtained. Furthermore, the sensor was applied to real-time visualization of changes in H and Al concentration in living cells, with great photostability and low cytotoxicity observed. Fluorescence images of H and Al were collected by using a fluorescence microscope in a dual-channel configuration, wherein they were labeled green and yellow, respectively.