| Deoxyribonucleic acid (DNA) is the main genetic material in the life, scientific research has shown that many of human genetic diseases are related to the mutation of bases in DNA sequence. Therefore, the detection of specific sequences and the mutation of bases in DNA are of great importance in numerous fields. Electrochemical DNA biosensor is a new type of biosensor developed in recent years. Based on the current analysis methods of sequence-specific detection of DNA, the methods of electrochemical detection of DNA are mainly used including labeling and labeling-free. Labeling method involves the chemical reaction, separation and purification steps, so it is complex, rather than labeling-free method is simple. But it involves the spread of the indicator itself which leads to high background current. Therefore, it is very important to design a kind of label-free, no easy diffusion of indicator and simple electrochemical DNA sensor.Copper ion is one of the essential trace elements in life, which plays an important role in life. However, excessive copper ions can cause serious health problems. Various approaches for detecting copper ions have been reported. The electrochemical methods have attracted a great deal of attention due to their simplicity, low cost, high sensitivity, good selectivity and so on. In this paper, a simple and non-labeled electrochemical DNA sensor was proposed by combining nickel hexacyanoferrate, gold nanoparticles, electrodeposition technology, DNA hybridization analysis technology and chemical modified electrodes. We also developed a electrochemical sensor for direct detection of copper ions based on the interaction between copper ions and the bases of DNA.This paper consists of two parts, the first part is the review, which mainly introduced the DNA, electrochemical DNA biosensor, the application of nickel hexacyanoferrate and the copper ion in biosensor. The second part is the research report, which is composed of two parts: 1.The label-free DNA electrochemical biosensor based on nickel hexacyanoferrate (NiHCF).A label-free electrochemical DNA sensor based on gold nanoparticles/NiHCF modified electrode was prepared. Probe DNA was covalently modified to the surface of gold nanoparticles/NiHCF modified electrode. The anodic peak current of NiHCF was detected by differential pulse voltammetry (DPV). The change of the anodic peak current of NiHCF before and after DNA hybridization was used as a response signal to realize the determination of the target DNA. The change of the anodic peak current of NiHCF had a linear response with the concentration of complementary DNA in the range of 1.0×10-12 M-1.0×10-8M, and detection limit was 3.2×10-13M (S/N=3).2. Detection of copper ion based on its concentration on the surface of DNA probe modified electrode.Based on the interaction between copper ion and DNA molecule, a simple method for detecting copper ion was designed. The probe DNA modified electrode was immersed in Na2HPO4-NaH2PO4 buffer solution containing copper ion. After a certain period of time, the copper ions (Cu2+) were concentrated at the DNA modified electrode. When a DPV potential signal was applied to the modified electrode,a current peak from the reduction of Cu2+ to Cu+can be observed at 0.15 V. Under the optimum experimental conditions, the peak current increases with the increasing of the concentration of copper ions. The relative current intensity had a linear response with the concentration of copper ions in the range of 2.0×10-6 M to 1.0×10-5 M and 2.0×10-5 M to 1.010-4M, and detection limit was 6.410-7M(S/N=3). |
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