Host-guest molecular recognition based fluorescence On-Off-On chemosensor for nanomolar level detection of Cu2+ and Cr2O72− ions: Application in XNOR logic gate and human lung cancer living cell imaging

Abstract

1,5-Dihydroxyanthraquinone (1,5-DHAQ) can form an inclusion complex with β-cyclodextrin (β-CD) strong base in aqueous solution, which can be employed to solubilize and stabilize the 1,5-DHAQ in pH 11 solution (1,5-DHAQ−2H;probe L). The hydrophobic nature of β-CD helps to dissolve and stabilize the probe L and hence permits its use as a probe in coordination reactions with cations and anions. This inclusion complex (β-CD:1,5-DHAQ−2H; probe LC) has been used for the colorimetric recognition behavior towards the Cu2+ and Cr2O72− ions by changing the color of the solution, which could be easily observed with the naked eye detection. Probe LC showed good fluorescence behavior upon interaction with different metal ions displayed strong fluorescence quenching (∼80%; switch-Off) with Cu2+ while remaining silent toward the tested cations. Moreover, that the LCCu2+ ensemble when tested toward different anions only dichromate (Cr2O72−) enable copper coordination (as CuCr2O7) and led to fluorescence enhancement (∼84%; switch-On). The detection limits of sensor LC to Cu2+ and LCCu2+ complex to Cr2O72− anion were estimated to be 10nM and 0.8nM, respectively. A theoretical study on molecular docking and density functional theory (DFT) calculations has been performed to demonstrate the binding of Cu2+ to Cr2O72− ions with probe LC. Furthermore, the propensity of probe LC as a bio-imaging fluorescent probe to detect Cu2+ ion and sequential detection of Cr2O72− ion by LCCu2+ in living cells (human lung cancer A549) by confocal laser scanning microscopy.