Sensitive and point-of-care detection of lead ion in river water mediated by terminal deoxynucleotidyl transferase

Excessive lead ions (Pb 2+ ) would make the human body suffer from anemia and neurological disorders. Therefore, it was of great significance to study an efficient method for the point-of-care (POC) detection of Pb 2+ . In this paper, an innovative method for sensitive detection of Pb 2+ in river water was proposed, which combined blood glucose meter signal transduction with terminal deoxynucleotidyl transferase (TdT) mediated DNA extension amplification strategy. The gold nanoparticle-modified electrode was used as the sensing interface, which was fabricated through the choline monolayer electrodeposition method. The target Pb 2+ initiated DNAzyme cyclic cleavage reaction on the magnetic bead, causing the substrate probe to generate 3′-OH terminus, which would induce the formation of polyadenine (polyA) sequences with the assistance of TdT. Ultimately, the numerous invertase tags on magnetic beads would be loaded on the sensing interface through the interaction between polyA and gold nanoparticles, which would catalyze the hydrolysis of sucrose to glucose with highly efficient enzymatic turnover, enabling the blood glucose meter for detection of Pb 2+ . The method exhibited a detection limit down to 0.6 pM, and can be used to detect Pb 2+ in river water and tap water with high selectivity, offering the method great potential to be applied in environmental monitoring and point-of-care diagnostic applications.