Engineering a DNA-cleaving DNAzyme and PCR into a simple sensor for zinc ion detection

The development of a simple sensor (9NL27-Zn) based on DNAzyme and PCR and aimed at the detection of low concentrations of zinc (II) ions is described. A specific Zn(II)-dependent DNAzyme (9NL27) with DNA-cleaving activity was employed. In the presence of zinc (II), the DNAzyme hydrolyzed DNA substrate into two pieces (5' and 3' fragments), forming 3'-terminal hydroxyl in the 5' fragment and 5'-phosphate in the 3' fragments. Subsequently, the 5' fragment left the DNAzyme and bound a short DNA template. The 5' fragment was used as a primer and extended a single-stranded full-length template by Taq polymerase. Finally, this full-length template was amplified by PCR. The amplified products had a quantitative relationship with Zn(II) concentration. Under our experimental conditions, the DNA sensor showed sensitivity (10 nM) and high specificity for zinc ion detection. After improvement of the DNA sensor, the detection limit can reach 1 nM. The simple DNA sensor may become a DNA model for the detection of trace amounts of other targets.