A novel label-free electrochemical aptasensor with one-step assembly process for rapid detection of lead (II) ions

Analysis and detection of lead is of great importance to environmental protection and human health. This paper reported a novel and label-free electrochemical aptasensor with one-step assembly process for rapid detection of lead (II) ions (Pb2+). As the specific recognition part, the Pb2+ aptamer was first screened out from single stranded deoxyribonucleic acid (ssDNA) library which owns a single stem-looped secondary structure by circular dichroism (CD) and isothermal titration calorimetry (ITC). The selected aptamer was a 33 nucleotides (nt) sequence named issAP17-Pb2+ and the dissociation constant (K-D) between it and Pb2+ was calculated to 1.13 x 10(-6) mol/L. Next, the aptamer was directly immobilized on the surface of screen-printed electrode (SPE) through unique consecutive adenines (polyA) linker in only one step without any other block groups. After the aptasensor was successfully constructed, Pb2+ was detected by dropping solution on the SPE and its response signal of electrochemical cyclic voltammetry (CV) and different pulse voltammetry (DPV) were recorded. The results of analytical performance examination revealed that the proposed aptasensor delivered an excellent calibration plot over the range of 0.1-1000 ng/mL towards Pb2+ along with a correlation coefficient (R-2) of 0.9931 and a detection limit (LOD) of 0.03 ng/mL (S/N = 3). Moreover, this aptasensor showed satisfactory reproducibility, good selectivity, great stability, and performed well in environmental and food samples. Considering the much lower cost of polyA assembly group and fast response advantage of electrochemistry characterizing method, our electrochemical aptasensor would provide a potential option for rapid and filed detection of Pb2+ in further practical application situations.