Study On Photoelectrochemical Methods Based On The New Quantum Dots Nanomaterical And Enzyme Auxiliary Signal Amplification Technique

Photoelectrochemistry is a potential analysis method with high selectivity,high sensitivity,simple instrument and easily miniaturization.It has been widely applied to the analysis and detection of various biomolecules.In recent decades,quantum dots have been applied in various fields due to their relatively narrow and tunable emission wavelengths,high quantum yield and special size effect.This work mainly explores the construction of photoelectrochemical biosensor analysis method based on quantum dots biological probe combined with signal amplification technology,and finally achieved the highly sensitive detection of target DNA,adenosine and thrombin.We have mainly carried out the following aspects:1.In this work,a novel CdS quantum dots was synthesized,which was used to develop a novel photoelectrochemical?PEC?sensing scaffold for sensitive detection of target DNA by cycling amplification strategy.First,the hairpin DNA was labeled with quantum dots by amino carboxyl interaction,then the DNA probe sequences were produced through the cyclic amplification technology.After the DNA probe was captured by the Au nanoparticles?NPs?on modified electrodes,high PEC signal of quantum dots was generated,which was used to achieve sensitive detection of DNA.The developed PEC bioassay with high sensitivity and good specificity has a great potential for detecting biomolecules with trace amounts in bioanalysis and clinical biomedicine.2.Herein,we successfully devised a novel photoelectrochemical?PEC?platform for ultrasensitive detection of adenosine by target-triggering cascade multiple cycle amplification based on the silver ion-assisted ion-exchange reaction with CdTe quantum dots?QDs?.In the presence of target adenosine,DNA s1 is released from the aptamer and then hybridizes with hairpin DNA?HP1?,which could initiate the cycling cleavage process under the reaction of nicking endonuclease.Then the product?DNA b?of cycle I could act as the“DNA trigger”of cycle II to further generate a large number of DNA s1,which again go back to cycle I,thus a cascade multiple DNA cycle amplification was carried out to produce abundant DNA c.These DNA c fragments with the cytosine?C?-rich loop were captured by magnetic beads,and numerous silver nanoclusters?Ag NCs?were synthesized by AgNO₃ and sodium borohydride.The dissolved Ag NCs released numerous silver ions which could induce ion exchange reaction with the CdTe QDs,thus resulting in greatly amplified change of photocurrent for target detection.The detection linear range for adenosine was 1.0 fM-10.0 nM with the detection limit of 0.5 fM.The present PEC strategy combining cascade multiple DNA cycle amplification and Ag ion-induced ion-exchange reaction with QDs provides new insight into rapid,and ultrasensitive PEC detection of different biomolecules,which showed great potential for detecting trace amounts in bioanalysis and clinical biomedicine.3.Based on the CdSe quantum dots?QDs?probe and DNA enzyme cyclic amplification technology,a linear chain hybridization reaction was constructed.The manganese porphyrin?MnPP?doping in the double stranded DNA hindered electron transfer,which led to the reduction of QDs PEC signal and achieved a sensitive detection of thrombin.When the target thrombin was present,it bound with S1 and S2,then S3 was released and hybridized with HP.In the presence of Mg²⁺,S3/HP was cut for producing DNA I.After the ITO electrodes were modified with TiO₂ and CdSe QDs,the capture DNA was attached to the CdSe QDs on the electrode,and then hybridized with DNA I to form a DNA bridge,which induced the long chain hybridization reaction with S4 and S5 on the electrode.Then the MnPP were doped in the double stranded DNA for blocking the electron transfer,which resulted in obvious decrease of QDs PEC signal for sensitive detection of thrombin.