A CHEF-driven fluorescent turn-on probe for sensitive and rapid Al³⁺ detection in live MDA-MB-231 cells

A novel fluorescent switch (PIMB) has been fabricated through a straightforward Schiff base reaction and exhibits highly selective sensing of Al³⁺ over other metal ions at physiological pH. Upon gradual and specific addition of Al³⁺, PIMB displays a pronounced "turn-on" fluorescence response, with an approximately 27-fold enhancement in emission intensity accompanied by a blue shift of about 34 nm in a MeOH/H₂O (1 : 1, v/v) medium. The detection limit and binding constant were determined to be on the order of 10^-9 M and 10⁵ M^-1, respectively. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were carried out to corroborate the experimental observations. Furthermore, PIMB demonstrates excellent potential as a biomarker, as evidenced by its successful application in live-cell imaging of human breast cancer cells (MDA-MB-231).