A Benzothiazole-Based Fluorescent Probe for Ratiometric Detection of Al³⁺ in Aqueous Medium and Living Cells

Aluminum is the third (after O and Si) most abundant metal in the earth’s crust and associates with neurological diseases when abnormal level of Al³⁺ occurs in nervous center. Developing highly sensitive and selective methods for Al³⁺ detection is of significant interest. In this work, we developed an excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) active fluorescent probe for ratiometric detection of Al³⁺ in aqueous medium and living cells. The <b>BTZ-SF</b> can detect Al³⁺ with high selectivity and a good linear relationship (<i>R</i>² = 0.9911) between fluorescence intensity ratio (<i>I</i>_476 nm/<i>I</i>_568 nm) and Al³⁺ concentration (0–100 μM). In addition, the detection limit was calculated as low as 2.2 μM. The single crystal structure of <b>BTZ-SF</b>–Al clearly exhibited the interaction between <b>BTZ-SF</b> and Al³⁺ with a hexa-coordinated structure. Furthermore, confocal fluorescence images of HeLa cell indicated that <b>BTZ-SF</b> could be used for monitoring Al³⁺ in living cells. Finally, a test strips experiment suggests that the <b>BTZ-SF</b> can recognize the Al³⁺ selectively accompanied by remarkable color change