Highly selective light-up Al3+ sensing by a coumarin based Schiff base probe: Subsequent phosphate sensing DNA binding and live cell imaging

Abstract

Abstract A coumarin based simple fluorescent “turn-on” probe, 4-Hydroxy-3-[(2-hydroxy-5-methoxybenzylidene)-amino]-chromen-2-one (HMC), to detect metal ion based on the chelation enhanced fluorescence (CHEF), was synthesized by condensing 3-amino-4-hydroxycoumarin and 2-hydroxy-5-methoxybenzaldehyde. It was found to be highly selective and sensitive sensor for Al3+ in 90% aqueous methanol (MeOH: 0.01 M HEPES Buffer; 9:1; v/v) at pH 7.4 in fluorescence spectroscopy. Fluorescence intensity enhancement along with 10 nm blue shift was observed only in the presence of Al3+. The HMC binds Al3+ in 1:1 stoichiometry with a binding constant, Ka = (9.9 ± 0.04) × 103 M−1 and the detection limit was calculated to be as low as 1.62 μM. The binding mode of interaction with Al3+ and the chelate complex formation was supported with the help of a 1H NMR spectroscopy titration, ESI–MS and also by theoretical studies. Moreover, the HMC·Al3+ ensemble subsequently detected the biologically important phosphate ions and nucleotides via fluorescence quenching. The live cell imaging study indicated that HMC is highly efficient in the detection of exogenous Al3+ in living cell.