A novel fluorescence “on-off-on” peptidyl probe for highly selective and consecutive detection of Cu2+ and glyphosate and its multi-functional applications

Copper ions (Cu²⁺) and glyphosate (Glyp) pose serious threats to human health and the ecological environment, and it is of great significance to conduct efficient and sensitive detection of these substances. Herein, a simple and novel fluorescence “on-off-on” peptidyl probe NGGH with 7-Nitro-2,1,3-benzoxadiazole (NBD) conjugated tripeptide (Gly-Gly-His-NH₂) was developed for relay detection of Cu²⁺ and glyphosate in 100 % aqueous solutions, and the limit of detections (LODs) reached up to 24.4 nM and 4.8 nM for Cu²⁺ and glyphosate, respectively. The binding stoichiometry of NGGH with Cu²⁺ was proved to be 1:1 based on Job's plot curve, fluorescence titration, ESI-HRMS and theoretical calculations. Notably, fluorescence imaging of Cu²⁺ and glyphosate revealed that NGGH was successfully applied on living cells and zebrafish larvae based on remarkable fluorescence behavior and low cytotoxicity. In addition, NGGH not only successfully determined Cu²⁺ and glyphosate in two real samples, but also applied to monitor the residues of Cu²⁺ and glyphosate in the surfaces of millet, kiwifruit and leaf. Furthermore, NGGH was fabricated into the fluorescence test strips and used for the visual detection of Cu²⁺ and glyphosate using naked eye under the 365 nm UV lamp. Finally, we constructed the sensitive INHIBIT logic gate based on the fluorescence “on-off-on” response effect characteristic.