The Preparation And Study Of Electrochemical Biosensors With Double Signal Amplification Function

Electrochemical biosensor technology is a new technology with multi-disciplinary intersection,which has attracted more and more researchers’attention because of its advantages of high sensitivity,high selectivity,simple operation,fast analysis and low cost.Nowadays,many advanced strategies are combined with the construction of electrochemical biosensor,which makes the technology more widely used.This paper makes the preparation of DNA probe,synthesis of new signal marker and nano composite materials,based on the Biotin-Avidin-System,catalytic hairpin assembly（CHA）and Au-S bond self-assembly technique,designs two kinds of electrochemical biosensor,which has the function of double signal amplification and respectively applied to the detection of heavy metals Pb²⁺in the Chinese traditional medicine/the lake and the detection of mi RNA-21in the cancer cell.The contents are as follows:（1）A Pb²⁺electrochemical biosensor based on DNA functionalized gold nanoparticles and nanocomposite modified electrode for double signal amplification.Heavy metal ion pollution brings serious risks to human health and the environment.Lead（II）(Pb²⁺)is a common toxic heavy metal ion,thus,the development of ingenious techniques to assess Pb contamination in samples is paramount.In this chapter,the DNA-functionalized Au NPs includes two types of DNA comprising a biotin labeled-enzyme DNA and a substrate strand DNA with a typical stem-loop structure,and a ferrocenelabeled 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 Au NPs 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 Au NPs and nanocomposite,the electrochemical detection signal of Pb²⁺was greatly improved.Under optimum conditions,the resultant biosensor bringed out a high sensitivity and selectivity for the determination of Pb²⁺with a minimum detection limit of 0.21 p M and linear range of 0.5 p M-50 n M and providing a promising scheme for the detection of target Pb²⁺.（2）A double signal amplification electrochemical Micro RNA biosensor based on catalytic hairpin assembly and bisferrocene label.As everyone knows,micro RNA is crucial for post-transcription gene regulation and is a new type of biomarker for many diseases.Therefore,it is important to develop a simple and highly sensitive method to detect low abundance mi RNA.In this chapter,a novel bisferrocene signal marker was synthesized containing two ferrocene units,which was placed at both ends of hairpin DNA,generating a probe of high-efficiency amplification signal.The electrochemical DNA sensors constructed using catalytic hairpin assembly（CHA）techniques are 100times more sensitive or even more than ten 10000 times higher than conventional electrochemical sensors and can directly detect RNA in cells.CHA technology and bisferrocene were integrated into the electrochemical biosensor to achieve double signal amplification.The biosensor achieved ultra-sensitive detection of mi RNA-21with a minimum detection limit of 0.1 f M and linear range of 0.2 f M-0.2 n M.This study provides an effective detection method for mi RNA-21 detection and opens up new possibilities for clinical diagnosis and treatment of diseases in the future.