DNA Walker Photoelectrochemical Nucleic Acid Sensor

Photoelectrochemical（PEC）biosensor can be summarized as a simple analysis device consisting of a sensing recognition unit and a photoelectric conversion unit.When the analyte interacts with the recognition unit,the generated biological signal is converted into a quantifiable electrical signal through the conversion unit.Due to its advantages of simple operation,high sensitivity and low background signal,the analytical method has attracted extensive attention in the field of disease detection and biological analysis.However,in practical application,the nucleic acid molecules to be detected have the problems of low concentration and high sequence similarity,so it is necessary to develop and build sensors with high sensitivity and selectivity.Among that,the selective of photoelectric materials and the design of sensing recognition strategy are the keys to build sensitive PEC biosensor.In this paper,based on the excellent performance of metal semiconductor nanomaterials in photoelectric conversion,PEC biosensors were constructed combined with effective target recognition strategy and signal amplification strategy to sensitive detect nucleic acid.It provides a basis for early diagnosis of cancer.The main research work is as follows:（1）The research of PEC detection of let-7a based on toehold-mediated strand displacement reaction and bismuth sulfide（Bi₂S₃）nanoflower for signal amplification.The 3D nanoflower-shaped Bi₂S₃ was synthesized by hydrothermal method,and combined with the enzyme-free toehold-mediated strand displacement reaction to carry out the target cycle to amplify the photocurrent signal process.Introducing alkaline phosphatase（ALP）into the system,when the target existed,the biological chain conjugated with ALP was replaced,so that the photocurrent signal would change,so as to achieve the specific detection of the target let-7a.（2）The research of Target dual-recycling-induced bipedal DNA Walker cascade amplification strategy for PEC biosensor based on Bi₂WO₆/Bi₂S₃.Combined with the energy level matching between semiconductors,the nanorod-shaped Bi₂S₃ and the nanosheet clusters into flower of bismuth tungstate（Bi₂WO₆）were synthesized by hydrothermal method.The composite material Bi₂WO₆/Bi₂S₃was constructed,and combined with the cascade amplification strategy.The silver sulfide quantum dots（Ag₂S QDs）were bound to the electrode surface,which further enhanced the photocurrent signal.When the target DNA TP53 were present,DNA Walker were produced through the cycleⅠprocess,and could participate in the next cycle,combined with the bioconjugate of Ag₂S to form a triplet.When the triplet was disintegrated,Ag₂S QDs were far away from the electrode,resulting in a decrease in the photocurrent.Thereby constructing a PEC biosensor that has had a sensitive response to DNA TP53.