Cathodic Photoelectrochemical Biosensors Based On Different Strategies For Signal Enhancement

With the development of society and the progress of economy,health issues have become a hot issue that people are concerned about.Practice has shown that being able to use analytical techniques to achieve accurate determination of biomarkers is of great significance for early clinical diagnosis of diseases.As a booming biomarker detection technology,photoelectrochemical immunosensing has shown good prospects due to its simple operation,low cost,low background interference,and high sensitivity.According to the properties of photoelectrodes,traditional photoelectrochemical immunosensing can be divided into photoanode type and photocathode type.Among them,the photocathode immunoassay has a good application prospect in actual biological detection due to its inherent ability to resist interference signals from potential reducing molecules.However,due to the limitation of the electron transfer mechanism of the cathode photoelectric material,its photocurrent signal is small,which is not conducive to the sensitive detection of the target.In view of this,this paper has developed three cathodic photoelectrochemical immunosensing platforms based on different signal enhancement strategies.The main contents are as follows:（1）Cathodic photoelectrochemical immunosensor based on bilirubin oxidase（BOD）label for sensitive detection of prostate specific antigen（PSA）.In this sensing system,the Au/Cd Se/Ni O photocathode is used as the sensor substrate,which can also be used to anchor the capture PSA antibody（Ab₁）while providing the cathode photocurrent.In order to increase host loading,abundant BOD molecules were labeled on signal antibody（Ab₂）with the assistance of carbon nanotube（CNT）,forming the Ab₂-BOD/CNT conjugate.When specific immunological recognition occurred,the BOD labeling could efficiently catalyze the reduction reaction of electron acceptor of dissolved oxygen,causing dramatically promoted cathodic photocurrent signal.By introducing this ingenious siginaling mechanism triggered by BOD,highly sensitive and specific detection of the target antigen can be achieved.（2）Cathode photoelectrochemical immunosensor based on photoanode enhancement,using the strategy of spatial separation of capture probe and photoanode to construct a photoelectrochemical immunosensing platform with high sensitivity and selectivity.The photoanode adopts Zn In₂S₄/Ti O₂-NTs sensitized structure to produce obvious and stable photocurrent output.The biocathode uses N-r GO/CNT/Co₃O₄ hybrid as the electrode substrate material.For N-r GO/CNT/Co₃O₄ hybrids,the synergistic effect of N atoms and Co atoms can effectively improve the catalytic activity and stability of the oxygen reduction reaction（ORR）,and increase the photocurrent intensity of the substrate material.When the target antigen（CEA）is present,the biocathode has a specific biorecognition effect,the formation of immunocomplex would cause the steric hindrance that inhibits the diffusion of solution species to the electrode,which leads to a decrease in the photocurrent of the system.Since the photoanode has a significant photocurrent response,and the photoanode does not need to incubate the biological sample to be detected,the sensor has higher selectivity and anti-interference ability compared with other sensors,and realizes the sensitive detection of the target antigen.（3）A cathode photoelectrochemical immunosensor integrating photocathode with photoanode is designed for accurate and sensitive detection of the biomarker of interleukin-6（IL-6）.Cu In Zn S/Ti O₂ sensitized structure modified on ITO electrode served as photoanode,whereas the Cu₂O micro-nano structure modified Cu foil was used as photocathode.The IL-6 antibody（Ab）was modified on the photocathode to fabricate a label-free cathode immunosensor.The proposed immunosensor has good anti-interference ability due to the biorecognition reaction occurred on photocathode.At the same time,the introduction of the photoanode makes the sensor have evident photocurrent and higher sensitivity.This sensor provides a new design idea for the subsequent development of other photoelectrochemical biosensors with excellent anti-interference performance.