Research On Photoelectrochemical Biosensor Based On Nanomaterials And Signal Amplification Strategy

Photoelectrochemical?PEC?biosensor converts the changes of photoelectric materials combined with molecular recognition into current signals.Due to the high sensitivity of photoelectrochemical analysis,it shows a bright application prospect in various fields.In order to realize highly sensitive detection,it is of great significance to synthesize photoelectric materials with excellent performance and introduce efficient and simple signal amplification strategy.The specific work is as follows:1.DNA network is used as a platform for the immobilization of sensitizer to construct highly sensitive photoelectrochemical sensors.Usually,the efficiency of sensitizers is limited by DNA double strand structure.Therefore,a photoelectrochemical aptasensor for detecting cancer marker vascular endothelial growth factor(VEGF₁₆₅)was constructed using DNA network containing a large number of double-stranded structures as the platform for the immobilization of sensitizer.DNA network structure is formed by the hybridization of four DNA single strand,which provides an ideal platform for the immobilization of methylene blue?MB?.Methylene blue promotes electron transfer through DNA helix structure,inhibits the recombination of electron-hole pairs produced by photoactive material g-C₃N₄ and enhances photocurrent.Specific recognition between target VEGF₁₆₅65 and the aptamer sequence contained in DNA network that destroys the DNA network structure immobilized by sensitizer,and the initially enhanced electron transfer process can be inhibited.Finally,the linear range was 100 fmol·L^-11 to 10 nmol·L^-11 and detection limit was 0.03 pmol·L^-1.In addition,this strategy can be used to detect disease markers corresponding to other aptamer sequences.2.ZnIn₂S₄P_4-X-X as photoactive material combined with target recycling amplification to construct highly sensitive photoelectrochemical sensorsThe metal sulfides and phosphides are usually used as photoelectric materials,but metal phosphorus sulfides are rarely studied.In order to synthesize a novel andefficient photoelectric material to construct a photoelectrochemical sensing system.It was found that ZnIn₂S₄P_4-X-X exhibited excellent photoelectrochemical properties compared with ZnIn₂S₄.Firstly,ZnIn₂S₄ was synthesized by hydrothermal method,and then phosphated to obtain ZnIn₂S₄P_4-X-X as a photoelectric material.By double specific nuclease?DSN?-aided target recycling,the single target microRNAs were exported to multiple nucleic acids,and multiple nucleic acids were used to immobilize the quencher SiO₂.Therefore,the initial electron transfer process of ZnIn₂S₄P_4-X-X can be suppressed,resulting in a significant decreased of photocurrent.Finally,the linear range was 100 fmol·L^-11 to 10 nmol·L^-11 anddetection limit was 33 fmol·L^-1.This strategy can be extended to construct a platform for the sensitive detection of other microRNAs,which can be used in biological analysis and clinical diagnosis.3.Silver vanadate nanoparticles combined with dual signal amplification strategy to construct photoelectrochemical sensor with near-zero background signalPhotoelectrochemical analysis usually adopts co-sensitized structure consisting of a variety of photoelectric materials to obtain high initial signals to detect biomarkers.However,the introduction of co-sensitization structure will produce background noise that can not be ignored,which limits the sensitivity of detection.In this experiment,a photoelectrochemical biosensor with near-zero background signal was designed for the ultrasensitive detection of vascular endothelial growth factor.The sensor is based on single photoactive material AgVO₃and dual signal amplification strategy.AgVO₃ nanoparticles,as a novel photoactive material in photoelectrochemical biosensors,exhibit excellent photoelectrochemical properties and can generate strong enough photoelectric current detection signals.In order to further improve the detection sensitivity,exonuclease III assisted target cycling and hybridization chain reaction were skillfully combined to achieve dual signal amplification,which converted a target protein into multiple DNA.At the same time,hybrid chain reaction provides an excellent platformfortheimmobilizationofphotoactivematerial AgVO₃toconstruct photoelectrochemical biosensors with near-zero background signal.Finally,the linear range was 10 fmol·L^-11 to 10 nmol·L^-11 and detection limit was 3 fmol·L^-1.This method provides a new strategy for detecting other proteins.