Fabrication Of Graphene-Based Electrochemical Biosensors And Their Application In Chinese Medicine Analysis

Nowadays,Chinese medicine has played more and more important role in the treatment of human diseases and health care.The species and quality control of traditional Chinese medicine therefore become a major concern of society.Chinese herbal medicines with accurate varieties and excellent quality usually contain effective and stable active ingredient and the content is in line with or even higher than the "Chinese Pharmacopoeia" content requirements,providing a safe and effective medicines’ environment for people’s rational drug use.So,it is a meaningful challenge for researchers to monitor the quality analysis and species identification of Chinese medicine.With the sudden development of modern drug analysis technology,graphene-based electrochemical sensors are widely applied for active ingredients analysis and species identification of traditional Chinese medicine.Such technologies can even achieve the identification of some easily confused Chinese herbs on the DNA molecular level.Compared with the traditional Chinese medicine analysis and identification technologies,electrochemical biosensors have a crowd of advantages,such as compact equipment,simple operation,good specificity,high sensitivity,fast speed and low cost,et al.Thus,in terms of analysis and identification of Chinese medicine,especially for detection of small active molecules with electrical activity,recognition of specific DNA sequence in Chinese herbs,and identification of adulterants,electrochemical sensors have a bright prospect in the future.Specific studies of this article are divided into the following three parts:Chapter Ⅰ: Sensitive detection of rutin in Flos Sophorae by a graphene-modified glassy carbon electrodeThe electrochemical one-step reduction method was used to fabricate the graphene-modified glassy carbon electrode as a sensing surface.Rutin,as the main electroactive ingredient in traditional Chinese medicine(Flos Sophorae),was successfully detected by this electrochemical sensor.The results showed that the peak current change of rutin had a superduper linear relationship with the different concentrations of rutin.The limit of detection was calculated as 23.2 nM.The electrochemical sensor was also applied for quantitative analysis of Chinese medicine Flos Sophorae and compound rutin tablets with satisfactory results.This method has provided a good testing platform for electroactive ingredient detection and quality control of Chinese medicine market.Chapter Ⅱ: DNA electrochemical biosensor based on graphene-gold particles nanocomposite for identification of F.thunbergii and F.cirrhosaTo enhance the sensitivity of the electrochemical biosensor,this experimental part was designed by using graphene and gold nanoparticles composite as sensing interfaces.After assembly of the nanocomposites,the specific thiolated DNA probe was immobilized via Au-S covalent effect.The DNA-modified biosensor only hybridized with 16-mer specific sequence in the 5s-r RNA region of F.thunbergii,but was noncomplementary with F.cirrhosa,thus achieving the accurate identification at DNA molecular level.The developed sensor provides a novel,fast,precise way to distinguish confused varieties in the traditional Chinese medicine market,and is significantly better than the DNA barcode technology in terms of expensive cost,time-consuming and complicated sequencing procedures and analysis process.Chapter Ⅲ: A photocatalytic renewable electrochemical biosensor for honokiol detection in Magnolia Officinalis and its Chinese herbal compound prescriptionTo resolve the differences of the electrical signal after electrode polished repeatedly and improve reuse ratio of the electrochemical biosensor,in this part,photocatalytic titanium dioxide nanomaterial was combined with graphene modified on glassy carbon electrode for sensor’s regeneration.And the designed electrochemical biosensor was applied to determinate honokiol in Magnolia Officinalis and its Chinese herbal compound prescription.Meanwhile,the sensor has achieved a rapid qualitative analysis of honokiol in real samples(Ageratum Liquid and Muxiang Shunqi Wan).After photocatalytic regeneration,the current responses were reduced nearly background signals,and achieve the repeated use of electrode.