Dual Signal Amplification Electrochemical Biosensor for Lead Cation

Herein, a sensitive electrochemical Pb²⁺ sensor was developed which based on DNA‐functionalized Au nanoparticles(AuNPs) and nanocomposite modified electrode. The DNA‐functionalized AuNPs includes two types of DNA, namely a Pb²⁺‐mediated DNAzyme comprising a biotin labeled‐enzyme DNA and a substrate strand DNA with a typical stem‐loop structure, and a ferrocene‐labeled linear signal DNA. Without Pb²⁺, the hairpin loop impeded biotin binding to avidin on the electrode. However,when the goal Pb²⁺ exists, the substratum strand was divided into two fragments that lead to the enzyme strand was substratumed on the electrode and biotin was admited by avidin, bringing about DNA‐functionalized AuNP(AuNPs) deposition on the electrode surface.The differential pulse voltammetry (DPV) was used to measure electrochemical response signals connect to signal DNA.For the amplification characters of the DNA‐functionalized AuNPs and nanocomposite, the electrochemical detection signal of Pb²⁺ was greatly improved and revealed high specificity. Under optimum conditions, the resultant biosensor bringed out a high sensitivity and selectivity for the determination of Pb²⁺. The proposed method was able to detect as low as picomolar Pb²⁺ concentrations.