Abstract: Objective: To establish a rapid method based on a linear palindromic DNAzyme for detecting lead ions as a heavy metal contaminant in tea and to meet the demand for rapid on-site detection of heavy metals in real samples. Methods: A lead-specific DNAzyme was designed and constructed, with palindromic sequences introduced at both ends of the enzyme strand to induce linear assembly, thereby enhancing structural stability and recognition efficiency. The enzyme and substrate strands were respectively labeled with BHQ1 and FAM to construct a fluorescence-based sensing system. Key parameters, including the concentrations of enzyme and substrate strands as well as reaction time, were optimized to determine the optimal experimental conditions. Results: Under the optimal conditions, the method exhibited excellent selectivity and sensitivity toward lead ions, with a limit of detection (LOD) as low as 0.012 nmol/L. The recoveries from spiked tea infusion samples ranged from 96.05% to 100.41%, indicating that the detection system has good applicability and reliability in complex sample matrices. Conclusion: The linear palindromic DNAzyme-based method is characterized by simple operation, rapidity, high selectivity, and high sensitivity. It can be effectively applied for the rapid detection of lead ions in tea and other real samples, providing a practical and efficient strategy for food safety monitoring.

Key words: palindromic structure; DNAzyme; lead ions; fluorescence-based detection