A New Fluorescence Turn-On Probe for Aluminum(III) with High Selectivity and Sensitivity, and its Application to Bioimaging

The development of novel selective probes with high sensitivity for the detection of Al(3+) is widely considered an important research goal due to the importance of such probes in medicine, living systems and the environment. Here, we describe a new fluorescent probe, N′-(4-diethylamino-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (1), for Al(3+). Probe 1 was evaluated in a solution of acetonitrile/water (1:1 v/v). Compared with previously reported probes for Al(3+), probe 1 can be synthesized easily and in high yield. A Job plot confirmed that probe 1 is able to complex Al(3+) in a 1:1 ratio, and the binding constant was determined to be 4.25×10(8) m(−1). Moreover, the detection limit was as low as 6.7×10(−9) m, suggesting that probe 1 has a high sensitivity. Common coexistent metal ions, such as K(+), Co(2+), Ca(2+), Ba(2+), Ni(2+), Pb(2+), Hg(2+), Ce(2+), Zn(2+), Cd(2+), Fe(3+), showed little or no interference in the detection of Al(3+) in solution, demonstrating the high selectivity of the probe. Finally, the ability of probe 1 to act as a fluorescent probe for Al(3+) in living systems was evaluated in Gram-negative bacteria, Escherichia coli, and confocal laser scanning microscopy confirmed its utility. The results of this study suggest that 1 has appropriate properties to be developed for application as a fluorescent probe of Al(3+) for use in biological studies.