The Construction Of Programmable DNA Biosensors Based On Semiconductors And Gold Nanoparticles

Cancer is one of the most serious health challenges in the 21st century.Regardless of the degree of human progress,it is a major driver of morbidity and mortality around the world.Therefore,the early detection of cancer is the primary key to effective cancer treatment.In this work,Cd Se/Zn S QDs,CdTe QDs,and Cd S semiconductors were prepared as photoelectrochemically responsive materials,and salt-induced the aggregation of Au NPs were used as photothermal output signals,assisted by superparamagnetic Fe₃O₄@Si O₂ microspheres combined with an entropy-driven biosignal amplification strategy,several photoelectrochemical and photothermal biosensor with good selectivity and high sensitivity was constructed and used for the detection of cancer markers micro RNA（mi RNA）and estrogen-like bisphenol A（BPA）.The main work is as follows:（1）Aided by programmable entropy-driven DNA amplifiers and superparamagnetic nanomaterials,a photoelectrochemical（PEC）biosensor based on exciton-plasmon interaction（EPI）was constructed.The target mi RNA-let-7a initiates an entropy-driven DNA amplifier,and the released Output DNA can open the partially hybridized double-stranded DNA modified on Fe₃O₄@Si O₂ particles.The released Au NPs-c DNA could fully hybridize with Cd Se/Zn S QDs-c DNA-1 and lead to a proportional decrease in the photocurrent of Cd Se/Zn S QDs.Its linear range was 10 a M～1 p M with a detection limit of 3.35 a M.Compared with conventional EPI-based solid-liquid interface electrode assembly,DNA hybridization and single-step electrode modification in solution phase significantly improved the electrode fabrication efficiency,reproducibility,and stability.（2）A photothermal biosensor for BPA detection was developed using salt-induced aggregation of Au NPs as photothermal agents.The target BPA binds to its aptamer and releases the target analogues.Target analogues indirectly amplify the target BPA signal through an entropy-driven cyclic amplification strategy and release single-stranded DNA.After separation by an applied magnetic-field,a pure and undisturbed sensor system containing only single-stranded DNA was obtained.Then,moderate amount of Au NPs and Na Cl were successively introduced into the system.As the concentration of BPA increased from small to large,more single-stranded DNA was protected onto the surface of Au NPs.At this time,under the irradiation of 808 nm laser,the temperature showed a linear distribution from high to low,and the color of the system changed from blue to pink.It has a linear range of 5 n M～50μM with a detection limit of 2.29 n M.This real-time,visual,and interference-free photothermal biosensor has great potential in disease diagnosis and clinical applications.（3）Using N-type Cd S semiconductors and P-type CdTe QDs as photocurrent signal response sources,a photoelectrochemical biosensor for simultaneous multiplex detection of mi RNAs（mi RNA-141 and mi RNA-155）was constructed.Coupling of photoelectrochemical responsive agents and corresponding quenchers to the DNA ends of the closed hairpin results in a drop of the photocurrent.The two targets undergo toehold-induced strand displacement reactions with two hairpin DNAs HP1 and HP2,respectively,thereby opening the hairpin DNA to form a firm double-stranded DNA.Due to the longer distance,Fe₃O₄@Si O₂@Cd S recovers its anodic photocurrent signal and CdTe QDs recovers its cathodic photocurrent signal.The simultaneous multiplex qualitative and quantitative detection of mi RNA-141 and mi RNA-155 could be achieved by magnetic separation.The biosensor for mi RNA-141 has a linear response to the target concentration of 50 f M～10 n M with a detection limit of 20.51 f M;while for mi RNA-155,the detection range was 50 f M～10 n M with a detection limit of 22.91 f M.Compared with the traditional single target substance detection,the multi-channel detection not only reduces the sensor fabrication cost,improving the sensor utilization rate,but also improves the detection accuracy.