Fluorescent chemosensor for Al(III) based on chelation-induced fluorescence enhancement and its application in live cells imaging

A tridentate Schiff base receptor BPB was synthesized by condensation of 2-(benzo[b]thiophen-2-yl)benzena-mine with salicylaldehyde in ethanolic medium and characterized by various spectral (FT-IR, H-1 NMR, C-13 NMR and mass) data. The methanolic solution of BPB was applied for the fluorescent sensing of metal ions dissolved in aqueous medium. The selectivity experiment revealed that the receptor BPB showed significant fluorescence enhancement at 430 nm in the presence of A(III) due to the chelation-induced fluorescence enhancement (CHEF) mechanism. Receptor BPB formed complex with Al(III) in 2:1 binding ratio with the estimated binding constant of K = 3.02 x 108 M-2. Without any interference from other tested metal ions, the receptor BPB can detect the concentration of Al(III) down to 256 nM. The receptor BPB showed good cell permeability and was applied for the qualitative and quantitative detection of intracellular Al(III) in A549 cell line (adenocarcinomic human alveolar basal epithelial cells) by using a confocal imaging technique