Ultrasensitive detection of lead ions based on a DNA-labelled DNAzyme sensor

Here, we report a facile approach for highly sensitive and selective detection of aqueous lead ions that uses a real-time quantitative polymerase chain reaction technology and a lead-dependent DNAzyme, termed GR-5. In this method, the substrate DNA is cleaved at the site of the adenosine ribonucleotide by GR-5 DNAzyme in the presence of lead ions, resulting in a decrease in template DNA available for PCR and a consequent change in signal detection (cycle threshold (Ct) value). This novel approach takes advantage of the exponential amplification of PCR and the specific recognition of the GR-5 lead-dependent DNAzyme to provide Pb2+-specific detection with an excellent linear relationship between Ct value and Pb2+ concentration within a range of 1–500 nM. The correlation coefficient of the standard curve was 0.9898, and the limit of detection was 0.7 nM. Moreover, this sensor showed good selectivity for Pb2+ ions over other metal ions.