Solvent-dependent fluorescent-colorimetric probe for dual monitoring of Al3+ and Cu2+ in aqueous solution: an application to bio-imaging

Abstract

A novel, quinoline-based smart probe L has been designed for the detection of Al³⁺ and Cu²⁺ at physiological range. The unprecedented solvent-dependent sensitivities of the probe L for simultaneous detection of Al³⁺ and Cu²⁺ ions with high selectivity and sensitivity have been observed for the first time. It displays quick responses through visible colorimetric as well as fluorogenic changes towards both Al³⁺ and Cu²⁺, as delineated by absorption and fluorescence titrations. The sensitivity of the fluorescence-based assay (12.6 nM) for Al³⁺ and (18.4 nM) for Cu²⁺ is far below the limit recommended in the World Health Organization (WHO) guidelines for drinking water. From ¹H NMR data, the Job plot and the ESI-MS spectrum, 1 : 2 stoichiometric complexations between L and both metals have been established. The geometry and spectral property of L and its metal complexes have been well rationalized by DFT calculations. This probe L has been tested as being highly suitable for mapping Al³⁺ and Cu²⁺ in human breast cancer cells, MCF7, thus providing a wonderful candidate for tracking Al³⁺ and Cu²⁺ in biological organisms and processes. The proposed chemosensor L has also been successfully applied for analysis of real samples.