Low-cost and highly efficient DNA biosensor for heavy metal ion using specific DNAzyme-modified microplate and portable glucometer-based detection mode

A simple and low-cost DNA sensing platform based on Pb 2+ -specific DNAzyme-modified microplate was successfully developed for highly sensitive monitoring of lead ion (Pb 2+ , one kind of toxic heavy metal ion) in the environmental samples coupling with a portable personal glucometer (PGM)-based detection mode. The detection cell was first prepared simply by means of immobilizing the DNAzyme on the streptavidin-modified microplate. Gold nanoparticle labeled with single-stranded DNA and invertase (Enz-AuNP-DNA) was utilized as the signal-transduction tag to produce PGM substrate (glucose). Upon addition of lead ion into the microplate, the substrate strand of the immobilized DNAzyme was catalytically cleaved by target Pb 2+ , and the newly generated single-strand DNA in the microplate could hybridize again with the single-stranded DNA on the Enz-AuNP-DNA. Accompanying with the Enz-AuNP-DNA, the carried invertase could convert sucrose into glucose. The as-produced glucose could be monitored by using a widely accessible PGM for in situ amplified digital readout. Based on Enz-AuNP-DNA amplification strategy, as low as 1.0 pM Pb 2+ could be detected under the optimal conditions. Moreover, the methodology also showed good reproducibility and high selectivity toward target Pb 2+ against other metal ions because of highly specific Pb 2+ -dependent DNAzyme, and was applicable for monitoring Pb 2+ in the naturally contaminated sewage and spiked drinking water samples.