A “turn-off” SERS aptasensor based DNAzyme-gold nanorod for ultrasensitive lead ion detection

It is great significance to precisely monitor lead (II) ions (Pb(2+)) for environment protection and human health monitoring. We designed a sensitive detection strategy for sensitive and selective determination of Pb(2+), based on a Pb(2+)-specific DNAzyme as the catalytic unit, Cy3-labeled DNA modified gold nanorods (AuNRs) as SERS reporter. Firstly, AuNRs surface were employed as a platform for the immobilization of thiolated probe DNA, and then hybridized with DNAzyme catalytic beacons. By taking advantage of DNAzyme digest, a molecular beacon, causes a “turn-off” SERS signal by disrupting the labeled probes. Under the optical conditions, the DNAzyme-AuNRs sensor system exhibited high sensitivity, acceptable stability and reproducibility with a wide linear range from 0.5 to 100 nM (R(2) = 0.9973), and an ultra-low detection limit of 0.01 nM. The proposed strategy has additional advantages of being less time-consuming, low-cost and remote query, and avoids the interference of some metals such as Fe(3+), Cd(2+), Ba(2+), Cu(2+), Zn(2+). The SERS biosensor system has been successfully applied for detecting Pb(2+) in real samples with a satisfactory result. The result indicated that the proposed sensing strategy not only enriches SERS platform of monitoring Pb(2+) but also exhibits potential for the point-of-care diagnostic application of the clinical screening in complicated biological samples.