Study On New Electrochemical Sensing Methods For Gene Identification And Heavy Metal Detection Of Traditional Chinese Medicine

Biosensor is a new sensor technology which integrates molecular biology,physics,chemistry and computer science.It has many advantages,such as sensitivity,rapidity,simplicity,non-destructive to test samples,not affected by solution color,and easy to miniaturize.In recent years,electrochemical and electrochemiluminescence methods have developed rapidly because of their advantages of sensitivity,wide detection range,low background signal and simple operation.This paper combines biosensors with electrochemistry and electrochemiluminescence,based on DNA hybridization chain reaction,host-guest recognition,Au-S bond self-assembly technology,two new electrochemical biosensors were designed by synthesizing nanomaterials,preparing bio-recognition probes and applied to the detection and identification of heavy metals in Chinese medicinal materials.The contents are as follows:?1?An electrochemical DNA homogeneous sensor without modification was constructed based on DNA hybridization chain reaction.Using a double hairpin DNA probe,a modified electrochemical DNA sensor was constructed by using au-S bond self-assembly.In this sensor,the 3'end of the double hairpin DNA probe is modified with ferrocene?Fc?and the 5'end is modified with sulfhydryl.When the probe DNA is not hybridized with the target DNA,the cyclic structure of the probe DNA makes the sulfhydryl group far away from the surface of the gold electrode under the action of applied potential.When probe DNA is hybridized with target DNA,the stem-loop structure of probe DNA is opened,which makes the surface of sulfhydryl contact with gold electrodes,which leads to the self-assembly reaction of Au-S and the formation of hairpin DNA structure.The quantitative detection of target was carried out by the change of the sensitive electrochemical signal of the Fc,the detection limit is as low as 3.4 pmol/L,and the high characteristic detection can be maintained under the condition of single base mismatch.?2?An electrochemiluminescence sensor based on hairpin DNA and host-guest recognition was developed for the detection of mercury ions in Salvia miltiorrhiza.An electrochemiluminescence?ECL?biosensor was constructed for the detection of mercury ions in Salvia miltiorrhiza by using Ru?bpy?₃²⁺/?-CD-AuNPs/Nafion complex and ferrocene labeled DNA probe?Fc-DNA?.The sensor consists of ECL luminescent substrate and ECL intensity switch.Ru?bpy?₃²⁺/?-CD-AuNPs/Nafion is assembled on glassy carbon electrode?GCE?to form a luminescent substrate and produce stable ECL signal;Fc-DNA probe acts as ECL signal switch was designed by molecular recognition strategy,Connecting?-CD-AuNPs with host-guest interaction of?-CD and Fc.Compared with previous mercury ion detection methods,this method has the characteristics of low background signal,high selectivity,simple instrument and fast operation.The Off-On electrochemiluminescent biosensor has a good linear response to Hg²⁺in the range of 0.04-800 ng/mL.The detection limit is 0.02 ng/mL?S/N=3?.