Research On Photoelectrochemical Biosensors Based On Target Cyclic Amplification And Perylene Derivatives

Photoelectochemical?PEC?biosensor,a newly developed analysis for biomolecular detection technology in recent year,has quickly become a research hotspot on account of the advantages of simple equipment,high sensitivity and low background signal.Research has shown that the generation of photocurrent in PEC analysis heavily depends on photoactive materials,electron-hole pair of which could be separated for relizing photoelectric conversion under the illumination.To improve the response signal,some signal amplification strategies are usually needed.Therefore,exploiting new photoactive materials and then combining with appropriate signal amplification strategy are of great significance for simple,sensitive,accurate and fast PEC biosensor.For these reasons,coupling of perylene derivatives as photoactive materials with the target cyclic amplification technology,self-enhenced PEC biosensor,wavelength-resolved PEC biosensor and dual-mode sensor are designed,respectively,to achieve the coreaction-free ultrosensitive detection,the high-throughput multi-component detection and the accurate detection of the complementary analysis.The research work is as follows:1.Novel D-A-D-Type supramolecular aggregates with high photoelectric activity for construction of ultrasensitive photoelectrochemical biosensorTraditional photoactive materials usually need to add electron donor/acceptor?D/A?in electrolyte solution or in situ generate through biocatalysis reaction to improve the photoelectric conversion efficiency.However,it suffered from the defect of low photoelectric conversion efficiency owing to the long distance and slow electron transfer between photoactive materials and electron donor/acceptor,which affect the sensitivity of analysis to a certain extent.To solve this problem,in this work,utilizing perylene anhydride?PTCA?as matrix and hydrazine?N₂H₄?as affinity reagent,a donor-acceptor-donor?D-A-D?-type hydrazine-functionalized perylene diimide derivative supramolecular?HPDS?aggregate consisting of electron-deficient perylene nucleus and electron-rich amino group was synthesized simplely by one-pot method.On the basis of the target dual-recycling-induced bipedal DNA walker cascade amplification,target was converted into numerous output DNAs,which could be immobilized on HPDS fabreicated substrate for assembling inert SiO₂ nanoparticles to quench photocurrent signal for the quantitative determination.Self-enhanced HPDS aggregates as photoactive material is non-essential to add any electron donor or acceptor reagent in testing electrolyte.Moreover,an effective cascade amplification strategy is introduced to effectively improve the detection sensitivity,which provides a new sensitive way for biological analysis and clinical diagnosis.2.Ultrasensitive photoelectrochemical detection of multiple metal ions based on wavelength-resolved dual-signal output triggered by click reactionThe multiple target detection on the same interface can improve the detection efficiency and reduce the cost.The simple,direct and effective method is to indicate diverse targets with different photoactive material signals.However,how to distinguish the generated signals is a serious challenge.In our work,combining metal ion cleavage cycle and utilizing photoactive substances PTCA and C₃N₄ which could generate wavelength-resolved photocurrent signals under the wavelength of 623 nm and 365 nm,ultrasensitive PEC biosensor was fabricated on the basis of the wavelength-resolved dual-signal output triggered by click reaction.Through the the Cu²⁺and ascorbic acid?AA?cocatalyzed click reaction,DNA fragments derived from the Pb²⁺and Mg²⁺dependent cleavage cycle of DNAzymes,respectively,were grafted efficiently on the same modified electrode,which thus could be subsequently used for immobilization of PTCA-labeled probe and C₃N₄-labeled probe to generate distinguishing dual-signal output for simultaneously sensitive detection of Pb²⁺,Cu²⁺and Mg²⁺.3.In situ formation of multifunctional DNA nanospheres for sensitive and accurate dual-mode biosensor with photoelectrochemical and elecreochemical assayMost quantitative determination relied heavily on single-modal readout,the accuracy of which was affected by the operation mode and experimental environment.In this work,a photoelectrochemical and electrochemical?PEC-EC?dual-mode biosensor was constructed.Using enzyme-assisted target cycle amplification to induce RCA reaction,a large number of DNA nanoparticles were produced in situ on TiO₂substrates,which were used to embed PDA⁺to form multifunctional DNA nanospheres.Narrow band gap PDA⁺with a high conversion efficiency can sensitize the wide band gap TiO₂ nanomaterials,so that the obvious enhanced PEC signal was obtain for the quantitative detection of the target.In addition,PDA⁺possessed the large planar?-?framework has excellent redox activity,obvious redox peak of which can be applied to electrochemical?EC?analysis.The integration of the two detection technologies can mutually verify the analysis results,effectively avoiding background signal and false positive signal,and enhancing the accuracy of sensitive detection.