Phenanthroline bridged bis(β-cyclodextrin)s/adamantane-carboxylic acid supramolecular complex as an efficient fluorescence sensor to Zn2+

Abstract

A water-soluble fluorescent Zn²⁺ sensor, 1,10-phenanthroline bridged bis(β-cyclodextrin) (1), was synthesized by “click chemistry”, and its fluorescence sensing behavior toward Zn²⁺ against various metal ions was investigated under physiological conditions. Significantly, 1 showed high selectivity and sensitivity toward Zn²⁺ with a limit of detection (LOD) down to 10⁻⁷ M. Moreover, the spectrophotometric studies demonstrated that after complexation with 1-admantanecarboxylic acid sodium salt (AdCA), the 1/AdCA complex gave much stronger binding affinity and lower LOD value toward Zn²⁺ through a cyclodextrin/substrate/Zn²⁺ triple recognition mode. The fluorescence stopped-flow experiments also indicated that the association rate of complex 1/AdCA to Zn²⁺ was much faster than compound 1 to the same ion. Furthermore, the fluorescence intensity of 1 and 1/AdCA was greatly enhanced after binding Zn²⁺ in living cells, and thus 1 and complex 1/AdCA could be considered as a biosensor for Zn²⁺ at the cellular level.