| A typical electrochemical biosensor based on an adapter uses the adapter as a biometric element to recognize the target object,converting the reactions generated by biological interactions into electrical signals for quantitative detection of the target.Although electrochemical aptamer biosensors have many advantages,such as good selectivity,low cost,and fast response,their detection is limited due to the low abundance of some detection targets and the limitations of the aptamer itself.Therefore,there is an urgent need to explore signal amplification strategies to make electrochemistry highly sensitive.This article is based on electrochemical aptamer biosensors and designs three different signal amplification strategies to achieve the detection of target substances.The specific content is as follows,with the main tasks as follows:(1)An electrochemical aptasensor with layered MoS2-Thi composite was established for the fast and sensitive detection of tetracycline(TC).In the absence of target,large numbers of Thi were loaded on the surface of MoS2 nanosheet to serve as electrochemical probes,resulting in an electrochemical signal.After target was added to the surface of electrode,a complex structure of aptamer-TC was produced on the modified electrode.Through intercalation and electrostatic interaction,the complex could be substantially modified onto the thionine and the peak currents of redox signal of thionine decreased.Therefore,the concentration of TC could be detected by the change of signal intensity.This method is simple and fast,providing an effective detection method for detecting TC.(2)An electrochemical sensing strategy was established for zearalenone(ZEN)detection on the basis of exonuclease Ⅰ(Exo Ⅰ)and branched hybridization chain reaction(bHCR)to amplify the signal.In the absence of ZEN,ZEN-cDNA cannot be exposed,so the subsequent bHCR process cannot be carried out.After adding the electrochemical indicator methylene blue(MB),only a small amount of signal can be obtained.While in the presence of ZEN,ZEN-cDNA could be exposed with the conjugation of the ZEN-apt and ZEN,which at the structure of a single strand could further initiate the bHCR resulting in the dendritic branching growth of DNA superstructures.Besides,the Exo Iassisted target recycling could provide larger amounts of signals involving fewer targets for the engine of following bHCR process.Moreover,the bHCR process in the model of the alternating extension by four hairpin probes,could yield appreciable numbers of extended double stranded DNA nanostructures,and feasibly provide the insertion site for electroactive species,profiting a more obvious signal.This amplification strategy utilizes the combination of enzyme cycle and nucleic acid amplification principles,providing a new detection method and means for detecting ZEN.(3)A novel electrochemical sensing strategy was established for ultrasensitive zearalenone(ZEN)detection on the basis of Co3O4/MoS2/Au and HCR to amplify the signal.In the absence of ZEN,the ZEN-apt/ZEN-cDNA complex could not trigger the amplification strategy.While in the presence of ZEN,ZEN-cDNA could be exposed with the conjugation of the ZEN-apt and ZEN,which at the structure of a single strand could further initiate the HCR,leading to alternating elongation of DNA growth,forming long double stranded lines,and providing insertion sites for MB,thus obtaining more obvious signals.This amplification strategy utilizes new nanocomposites combined with nucleic acid amplification,providing a new detection approach and method for ZEN detection. |
