Ultrasensitive electrochemical/visual colorimetric dual-mode biosensing of Pb2+ based on G-quadruplex DNAzyme and 2D bimetallic porphyrin MOF derived nanocomposites

Rapid and accurate detection of lead (II) ions (Pb 2+ ) is of great importance for food and environmental safety. In this work, we developed a dual-mode biosensing strategy for Pb 2+ determination based on a bimetallic two-dimensional porphyrinic MOF nanocomposite and G-quadruplex DNAzyme, combined with enzyme-like synergistic catalysis and DNA hybridization chain reaction (HCR) amplification. The sensing platform provides both electrochemical and visual colorimetric readouts, enabling highly sensitive detection under different application scenarios. Benefiting from the coupling of HCR with the cooperative catalysis of the G-quadruplex DNAzyme and MOF nanocomposite, the assay shows markedly enhanced sensitivity. In the electrochemical mode, the sensor achieves a limit of detection of 0.4 nM with a linear range from 1 to 10,000 nM. In the colorimetric mode, the assay affords a detection limit of 2.6 nM with a linear range from 10 to 10,000 nM. This dual-mode Pb 2+ biosensing strategy shows promising potential for food safety monitoring and environmental pollution analysis, and provides a useful reference for the development of new techniques for trace heavy-metal ion detection.