Based On Oligonucleotide To Building High Sensitive Electrochemical Biosensors

The electrochemical biosensor is a device that is sensitive to biological substance and converts its concentration into electrical signals.Protein,DNA and microRNA(miRNA)are indispensable constituent parts of the human body and play important roles in the normal operation of the body,which are closely related to human health.Therefore,rapid and sensitive detection of these biomolecules by Electrochemical biosensor possesses great value.Oligonucleotides can proceed a series of replication,connection and some other process of nucleic acid strands by the principle of complementary base pairing,This principle also provides the possibility of building a variety of biosensors based on oligonucleotides.And the sensors have good selective and stability.The application of nanomaterials to the sensor can also increase its specific surface area and conductivity,which can amplify the signal.In addition,the introduction of bio-amplification technology can further increase the electric signal and significantly improve the detection sensitivity.Based on these points,this paper carried out the following tasks:(1)Sulfur and nitrogen co-doped reduced graphene oxide(SN-rGO)is firstly prepared by a simple reflux method and used for supporting substrate of biosensor.The thrombin sensor was constracted with a tetrahedral DNA(T-DNA)probe,target competition system and hybridization chain reaction(HCR)signal amplification strategy.Finally,the cDNAs trigger HCR to immobilized abundant horseradish peroxidase(HRP)which results in a great current response by the catalysis of HRP to the hydrogen peroxide + hydroquinone system.The thrombin biosensor presents a good linear relationship between 0.1 pmol L-1 and 10 nmol L-1,the detection limit is 11.6 fmol L-1(S/N=3).(2)A highly sensitive biosensor for detecting platelet-derived growth factor-BB(PDGF-BB)is developed with Se-doped multi-walled carbon nanotubes(MWCNTs)-graphene hybrids for electrode supporting substrate,hemin/G-quadruplex as trace labels and Y-shaped DNA-aided target recycling for signal amplification.The developed biosensor shows a linear range from 0.1 pmol L-1 to 10 nmol L"1 and a detection limit of 12 fmol L-1(S/N=3),and possesses good selectivity and stability.(3)A simple hydrothermal method was used for the preparation of coralloid stannic oxide-graphene hybrids as electrode substrate.The DNA fragment is recycled by duplication-incision-replacement process in the effect of two kind of enzyme,then the gold nanoparticals(AuNPs)serve as signal probe carriers.After linking plentiful streptavidin-conjugated alkaline phosphatase,the electrochemical-chemical-chemical oxidoreduction reaction were produced by the action of ferrocene methanol,tris(2-carboxyethyl)phosphine and 1-ascorbic acid 2-phosphate to amplify electrochemical signal.The linear range of this DNA biosensor is 1 fmol L-1-10 pmol L-1,and the detection limit is 1.25×10-17 mol L-1(S/N=3).(4)A sandwich-type electrochemical biosensing platform is constructed based on carbon sphere-MoS2(CS-MoS2),AuNPs and target recycling amplification of catalyzed hairpin assembly(CHA)strategy for monitoring of miRNA.The CS-MoS2 has a large specific surface area,high stability and good dispersibility,the CHA signal amplification strategy makes target cycling and produces many double stranded DNA.This miRNA sensor exhibits a wide linear relation between 1×10-16 and 1×10-10 mol L-1,and the detection limit down to 1.6×10-17 mol L-1(S/N=3).