Graphene Nucleic Acid Biosensor And Its Application

It has been more than 100 years since the discovery of nucleic acid.Nucleic acid is a kind of biological macromolecular compound that is mainly located in the cell by the polymerization of many nucleotides.It is the carrier of the genetic information of organisms,including DNA and RNA.Nucleic acid molecule detection technology can be used to detect whether humans and animals and plants are infected by pathogens,as well as for genetic disease or cancer risk detection,personal medicine to provide supplementary reference,and whether water bodies have microbial contamination detection.So far,many nucleic acid detection methods have been developed,such as real-time quantitative fluorescence PCR and fluorescence in situ hybridization,but all of them have certain application limitations.Therefore,it is of great significance to establish a nucleic acid detection method with high efficiency,reliability,high sensitivity,high selectivity and high specificity is also of great significance.With the development of interdisciplinary,the research and development of biosensors has become a hot spot in the scientific community.Biosensor is an analytical device that combines the biometric identification system and the signal conversion system properly,responds to the analyte in the sample,and converts the biological signal into electrical,optical,acoustic that can be detected,so as to detect the analyte.Biosensors are widely used,not only for detecting proteins,bacteria,viruses,metal ions,but also for single-molecule level analysis.They are agile,accurate,multi-functional and portable.At present,the research of nucleic acid biosensors has made great progress and has developed into a frontier research hot spot.In recent years,nano field effect transistor nucleic acid biosensors were a novel nucleic acid biosensor based on nanomaterials(such as graphene,carbon nanotubes,nanowires).This is mainly because nanomaterials have the unique properties of surface effect,small size effect,quantum size effect and macroscopic quantum tunneling effect,which makes the nucleic acid biosensor have the characteristics of high sensitivity,good selectivity,simple operation,compact integration.Compared with nucleic acid molecule detection technology,it has unique advantages and was very suitable for the detection of nucleic acid molecules.In this paper,the nanomaterial graphene was firstly prepared by chemical vapor deposition as a conductive channel,and then the field effect transistor nucleic acid biosensor was developed and applied to the biological recognition between guanine riboswitch and ligand.Graphene has unique physical properties,such as large specific surface area,good electrical conductivity and high carrier mobility,these excellent properties of graphene can improve the sensitivity,selectivity and specificity of nucleic acid sensor detection.In this experiment,the nucleic acid molecule and the target molecule are fixed on the graphene surface by the hybridization principle of the nucleic acid molecule.The combination of nucleic acid molecules and target molecules leads to the change of surface potential of graphene,and the corresponding relationship between the change of electrical signal and the concentration of the measured molecules was established to achieve the purpose of molecular detection.This paper consists of six parts.The first chapter is the introduction,which mainly introduces the important role of nucleic acid,the research progress of nucleic acid biosensor and the application of graphene in biosensor.The second chapter mainly introduces the preparation method of graphene,the transfer of graphene film,the preparation and working principle of graphene field effect transistor(G-FET)and the electrical property test.The third chapter is RNA detection based on graphene field effect transistor biosensor.The graphene prepared by the above method was used as an electron channel to manufacture a G-FET biosensor with single-stranded DNA as a probe and complementary.The strand RNA was used as a target for label-free detection.These sensors are highly sensitive and can detect RNA as low as 0.1 fM,two orders of magnitude lower than previously reported(10 fM).In addition,G-FET biosensors can easily distinguish between target RNA and non-complementary RNA,showing high selectivity for RNA detection.The fourth chapter is based on the comparison of the PNA probe and the DNA probe of the graphene RNA biosensor.Using peptide nucleic acid(PNA)as a probe,it was proved that the PNA-RNA hybridization system had higher thermal stability,shortened the detection time,and could realize the detection of trace RNA as low as 0.1 aM.The fifth chapter is a graphene biosensor for biorecognition between guanine riboswitch and ligand.In this paper,a label-free graphene field effect transistor(G-FET)biosensor has been developed to detect the binding interactions between GR and four purine analog ligand molecules(GUA,6GU,2BP,XAN).The equilibrium dissociation constants K_D and binding free energyΔG of the four guanine riboswitch pairs(GR-GUA,GR-6GU,GR-2BP,GR-XAN)were obtained by the G-FET biosensor,and the results are comparable with the calculated by molecular dynamics simulation and previous reports.We demonstrated that the G-FET biosensor can be used as affnity biosensors to quantify biomolecular interactions.The G-FET biosensor may serve as a new tool for disease diagnosis,genetic screening and drug discovery.The sixth chapter is the summarizes,that summarizes the main conclusions and innovations of this research topic.