A DNAzyme-based Electrochemical Impedance Biosensor for Highly Sensitive Detection of Cu2+ Ions in Aqueous Solution

We developed a simple, label-free, DNAzyme-based electrochemical impedance sensor for highly sensitive detection of Cu2+ ions in aqueous solution. A complex of Cu2+-dependent DNAzyme and its corresponding substrate was immobilized on the gold electrode surface though Au-S bond. In the presence of Cu2+ ions, the cleavage of DNAzyme resulted in a significant change in the charge transfer resistance signal intensity. The resistance signal change correlated with the concentration of Cu2+ ions. The proposed sensor showed excellent sensitivity and selectivity. The limit of detection of this sensor is 5 nM, which is far below the limit of Cu2+ ions (similar to 20 mu M) mandated by United States Environmental Protection Agency (EPA). A series of metal ions, such as Ca2+, Mg2+, Mn2+, Cr3+, Pb2+, Zn2+, Co2+, and Ni2+, have little interference with the detection of Cu2+ ions.