Fluorescence detection of Cu²⁺ and tetracycline based on DNA-mediated formation of dual-color coordination complexes

Abundant hazardous substances are generated with the rapid development of human modernization. Fluorescent probes have been widely applied in the determination of toxic substances. To achieve atom economy and high-density integration, it is imperative to develop multifunctional fluorescent probes. In this work, a coordination complex of DNA and Mg²⁺ was designed as a bifunctional fluorescent probe for the detection of two hazardous substances (Cu²⁺ and tetracycline). With adding Cu²⁺ to the DNA/Mg²⁺ complex in the presence of ascorbate, Cu²⁺ coordinated with DNA and was reduced by ascorbate to form nanoclusters, which emitted red luminescence at 600 nm. For the detection of Cu²⁺, the DNA/Mg²⁺ complex exhibited a quantitative range of 10-80 μM, a detection limit of 1.1 μM and a response time of 1 min. When tetracycline encountered the DNA/Mg²⁺ complex, tetracycline coordinated with Mg²⁺, which sensitized the green fluorescence of tetracycline at 500 nm. Tetracycline was detected by the DNA/Mg²⁺ complex in the concentration range from 1 to 80 μM with a detection limit of 0.14 μM and a response time of 1 min. The bifunctional property endowed the DNA/Mg²⁺ complex with the advantages of atom economy and high-density integration. The DNA/Mg²⁺ complex was applied to detect Cu²⁺ and tetracycline in actual samples, and the result proved that the DNA/Mg²⁺ complex was applicable in real samples.