Chemiluminescence detection of lead (II) using '8-17' DNAzyme and hemin/G-quadruplex with high sensitivity and selectivity

It is important to design new ways with high specificity and sensitivity to detect lead (II). Here, '8-17' DNAzyme was used as a Pb²⁺-dependent probe with high sensibility and selectivity based on chemiluminescence (CL). When Pb²⁺ was present, the substrate strand was cleaved and the active hemin/G-quadruplex DNAzyme structure was formed in the presence of another sequence which contained two parts, one could be complementary with part of the substrate strand and the other was a G rich subunit. The active hemin/G-quadruplex DNAzyme structure could catalyze luminol oxidation and quantitative analysis of Pb²⁺ was carried out according to the CL of luminol. Results showed that CL intensity of luminol at 452 nm had a linear relation with the concentration of Pb²⁺ in the range from 5 nM to 1 μM, and the limit of detection was 0.79 nM (S/N = 3). This method was also used to detect the contents of Pb²⁺ in lake water and tobacco and the results (62.4 ± 4.0 nM and 15.2 ± 2.2 nM, respectively) were extremely closed to those of inductively coupled plasma-mass spectrometry (ICP-MS) (57.0 ± 1.4 nM and 14.5 ± 0.91 nM, respectively).