Structural and positional impact on DNAzyme-based electrochemical sensors for metal ions

The rapid, accurate and convenient detection of heavy metal is very important to public health. Here, we developed a DNAzyme-based electrochemical sensor for Pb²⁺. A DNAzyme-including and Pb²⁺ active probe was anchored to the biosensing interface, based on the well-defined self-assembled, three-dimensional DNA nanostructure. The results indicate that the detection performance depends on the change of distances between the methylene blue and the electrode surface. The limit of detection (LOD) could reach the concentration of 0.01 μM Pb²⁺, and the signal change shows semi-logarithmic relationship with the concentration of Pb²⁺ from 0.01 μM to 100 μM. The biosensor also presents good stability and specificity to detect Pb²⁺ in tap or river water. This method not only provides promising approach for improving the performance of tetrahedra in detecting Pb²⁺, but helps deepen the understanding of tetrahedral structure design and how the position of electroactive groups affects the performance of electrochemical sensing.