Photoelectrochemical Biosensing Systems Based On Novel Signal Transduction Modes

In recent years,photoelectrochemical?PEC?biosensing has shown good application prospects in various target detection due to its advantages such as simple device,convenient operation,low cost,and low background signal.The photoelectrode is the core component of the PEC biosensor,which generates the current detection signal under the excitation of the radiation light source.The photocurrent response of the photoelectrode greatly affects the sensitivity of the PEC biosensor,and its stability directly determines the signal stability of the PEC biosensor.Previously reported photoelectrochemical biosensors often rely on photoelectrodes as both a signal source and a biometric response platform.In such a design,the side effects between the photoelectrode and a potentially reducing substance in the biological medium and the interaction between the photoelectrode and the biomolecule will inevitably affect the performance of the corresponding PEC sensor.To address the above problems,an effective solution was proposed from the perspective of the sensor construction strategy.This thesis reports three new types of photoelectrochemical sensing platforms with signal conduction mode to solve the problems of coexisting reducing interference and false positive signals when detecting biological samples.The main contents are as follows:?1?A high-performance photoelectrochemical cell-sensing platform was designed,which used signal photoanode and sensing biocathode.In the photoelectrochemical system,the photoanode was only used to generate obvious and stable photocurrent signals,while the biocathode was used to identify and capture target cells.Based on CNQDs/MoS₂/TiO₂/ITO ternary heterostructure photoanode,it has excellent PEC performance,and the cell sensor has high sensitivity and stability to MCF-7 cells.In addition,due to the spatial separation of photoanode and bioelectrode,the cell sensor avoids the interference of other cells and coexisting reducing substances,and has higher selectivity.?2?The solid-state nanochannel has a broad application prospect in the field of photoelectrochemical biological analysis.A novel photoelectrochemical biosensor system based on DNA modified nonporous anodized alumina nano channel?AAO?was designed to detect telomerase?TE?activity with high sensitivity.Specifically,the telomerase primer sequence?TS?was initially fixed in the AAO nanochannel and then extended by telomerase in the presence of dNTPs.In the presence of hemin,one end of single strand assisted DNA?a-DNA?can form G-quadruplex structure,play the role of peroxidase,which can induce the formation of biocatalytic precipitation reaction to produce insoluble precipitates and block the nanopore.Since the inhibition signal of the photoelectrode is related to TE-activated TS chain extension,a novel nanochannel PEC bioassay can be implemented to detect TE activity.?3?A sensitive and reliable double signal biosensor method was designed to measure the activity of UDG by coupling PEC and EC probes on one electrode.Using Au/TiO₂ as substrate,the substrate DNA?sDNA?was fixed and AgInS₂ quantum dots?AIS QDs?was modified at the end of the s DNA.In the presence of UDG,the base of uracil was removed from sDNA,and the resulting AP site can be cleaved by Endo.IV.In this case,AIS QDs,a photoelectrochemical probe,breaks away from the electrode,resulting in a downward trend of PEC signal.After the assembly of aDNA,the HCR was triggered and the EC probe?ferrocene?was introduced.The EC signal produced was on the rise.Using PEC and EC dual-signal modes to detect UDG activity,accurate analysis of UDG activity in living cells was achieved.By changing the recognition sites,this dual signal strategy can be extended to the diagnosis of other key biological factors in real samples.