Highly Sensitive Fluorescence Imaging of Zn²⁺ and Cu²⁺ in Living Cells with Signal Amplification Based on Functional DNA Self-Assembly

Intracellular trace Zn²⁺ and Cu²⁺ play important roles in the regulation of cell function. Considering the limitations of existing metal ion detection methods regarding sensitivity and applicability to living cells, an amplification strategy based on functional DNA self-assembly under DNAzyme catalysis to improve the sensitivity of intracellular Zn²⁺ and Cu²⁺ imaging is reported. In this process, metal ions as cofactor can activate the catalysis of DNAzyme to shear substrate chains, and each broken substrate chain can initiate consecutive hybridizations of hairpin probes (Hx) labeled with fluorophore, which can reflect the information on a single metal ion with multiple fluorophores. The detection limit can reach nearly 80 pM and high-sensitivity fluorescence imaging of intracellular Zn²⁺ and Cu²⁺ can be achieved. The results are important for research on cell function regulation associated with trace Zn²⁺ and Cu²⁺. This approach is also a new way to improve the sensitivity of other trace metal ion imaging.