A highly selective turn-off fluorescent probe for Cu(ii) based on a dansyl derivative and its application in living cell imaging

Abstract

A novel dansyl derivative (1) was designed and synthesized with high yield. It is highly selective for Cu²⁺ over other competing metal ions such as Ca²⁺, Co²⁺, Cr³⁺, Cu⁺, Fe²⁺, Ga³⁺, Hg²⁺, Mg²⁺, Na⁺, Ni²⁺ and Pb²⁺. Zn²⁺ and Fe³⁺ only slightly changed the fluorescence of probe 1. The linear relationship between fluorescence intensity and Cu²⁺ concentration indicates that 1 can be used for quantification. The binding ratio of probe 1 to Cu²⁺ was found to be 1 : 1 according to Job's plot experiments. Probe 1 can be used in a broad pH value window ranging from 5 to 11. The limit of detection (LOD) based on 3 × δ_blank/k was calculated with a value as low as 1.6 × 10⁻⁶ M for Cu²⁺. Additionally, the association constant of probe 1 − Cu²⁺ complexes was found to be 5.08 × 10⁴ M⁻¹. Moreover, fluorescence microscopy experiments showed that 1 can be used as a fluorescent probe for evaluating the presence of exogenous Cu²⁺ in living cells.