Fluorescence Regulation of Copper Nanoclusters via DNA Template Manipulation toward Design of a High Signal-to-Noise Ratio Biosensor

Because of bioaccumulation of food chain and disability of biodegradation, concentration of toxic mercury ions (Hg²⁺) in the environment dramatically varies from picomolar to micromolar, indicating the importance of well-performed Hg²⁺ analytical methods. Herein, reticular DNA is constructed by introducing thymine (T)-Hg²⁺-T nodes in poly(T) DNA, and copper nanoclusters (CuNCs) with aggregate morphology are prepared using this reticular DNA as a template. Intriguingly, the prepared CuNCs exhibit enhanced fluorescence. Meanwhile, the reticular DNA reveals evident resistance to enzyme digestion, further clarifying the fluorescence enhancement of CuNCs. Relying on the dual function of DNA manipulation, a high signal-to-noise ratio biosensor is designed. This analytical approach can quantify Hg²⁺ in a very wide range (50 pM to 500 μM) with an ultralow detection limit (16 pM). Besides, depending on the specific interaction between Hg²⁺ and reduced l-glutathione (GSH), this biosensor is able to evaluate the inhibition of GSH toward Hg²⁺. In addition, pollution of Hg²⁺ in three lakes is tested using this method, and the obtained results are in accord with those from inductively coupled plasma mass spectrometry. In general, this work provides an alternative way to regulate the properties of DNA-templated nanomaterials and indicates the applicability of this way by fabricating an advanced biosensor.