Electrochemical Biosensor Based On Signal Amplification Strategy For Detection Of Genes And Heavy Metal Mercury In Chinese Medicinal Materials

Biosensor is a kind of detection instrument which integrates molecular biology,physics,chemistry,computer science and other disciplines and can transform biological reaction into electrical signal.Biosensors have attracted extensive attention because of their high sensitivity,good selectivity,easy operation and repeatability.At present,biosensors have become a cutting-edge subject in the field of biology and medicine.Heavy metal pollution is a global problem.Mercury,a heavy metal,is a neurotoxin that can damage human organs,causing kidney and lung damage.According to the US Environmental Protection Agency（EPA）,the maximum mercury contamination level in drinking water should be less than 2×10^-6 g L^-1(about 1×10^-8mol L^-1).Therefore,the detection of heavy metal mercury is very important,and most of the current heavy metal detection methods have problems such as complex operation process,high cost,time-consuming and laborious detection process,and the sensitivity and reproducibility need to be improved.For these reasons,it is important to develop special equipment for rapid,sensitive and selective determination of mercury ions.Focusing on the research and construction of simple,convenient,low concentration and high sensitivity electrochemical biosensors for analysis and detection,this paper constructed two different electrochemical DNA sensors based on electrochemical bonding method for the detection of DNA and heavy metal mercury ions respectively.The specific content is as follows:1.Based on electrochemical bonding,a non-modified sensing strategy is constructed in a homogeneous solution for the detection and analysis of target DNA.The 3’end and 5’ end of the double hairpin probe are respectively labeled with the electroactive substances tetraferrocene（TrtaFc）and sulfhydryl（SH）.Because the steric effect of the probe hinders the connection of SH with the electrode surface,when hybridized with the target DNA,the double hairpin ring structure of the probe opens.With the help of electric potential,SH can reach the electrode surface and form gold with the electrode.The self-assembly of sulfur bond（Au-S）and the electrochemical signal of TrtaFc are recorded by electrochemical workstation for real-time detection.The experimental results found that in the range of 0.18-1800 pM,the target DNA concentration and the current signal showed a good linear relationship,and the detection limit was 0.14 pM（S/N=3）.This homogeneous strategy is designed to achieve highly specific and sensitive determination of DNA.2.In a homogeneous system,a non-modified electrochemical DNA sensor was constructed based on electrochemical bonding and catalytic hairpin self-assembly for the detection of heavy metal mercury ions.In this work,we designed three hairpin probes with circular structures.Both ends of the H1 probe were modified with sulfhydryl groups,and both ends of the H2 and H3 probes were modified with TrtaFc signal markers.The specific coordination between thymine and mercury ion(T-Hg²⁺-T)induces the self-assembly of the catalyzed hairpin with the help of auxiliary DNA.The probe DNA hybridizes with the target mercury ion to form a rigid tetrahedral structure.After the voltage is applied,SH reaches the electrode surface,and four TrtaFc signal markers also contact the electrode surface to produce highly sensitive electrochemical signals.Realize dual-signal amplification based on catalytic hairpin self-assembly and TrtaFc aptamer.The experimental results found that within the mercury ion detection range of 0.2-2000 pM,the current signal value showed a good linear relationship,and the detection limit was 0.12 pM（S/N=3）.