Anti-interference Photocathodic Biosensors Based On Inorganic Nanocomposites

The accurate diagnosis of common critical diseases is essential and beneficial to the early detection and treatment,so as to guarantee the health of people.Photoelectrochemical(PEC)sensor is a newly developed sensing technology based on the organic combination of the photoelectrochemical technique with electrochemical analysis.It not only inherits the advantages of simple device,convenient operation,low cost,easy integration and miniaturization of the electrochemical biosensor,but also has low background interference due to the different energy forms of excitation signal and detection signal.Photoanodic biosensors have been wildly investigated becaused of the high PEC signal output and high sensitivity.However,as the reaction occurred at the surface of the photoanode is an electronic oxidation reaction,the photoanode is susceptible to interference from ascorbic acid,dopamine,glutathione and other reducing substances in actual biological samples,which will affect the accuracy of the test results.Photocathodic biosensors possess excellent resistance to real biological sample multicomponent reducing species,but due to the inherent photocathodic electron transfer limitations of the p-type materials,the photocurrent signal is usually low,which is not conducive to sensitive detection of targets.Moreover,in addition to the interference of reducing substances,the adsorption of proteins in serum also affects the sensitivity and accuracy of the biosensor for actual sample analysis.To solve the above problems,effective improvement methods are put forward in this thesis according to the building strategy of PEC biosensor and photoactive material sensitizing.This thesis reports three kinds of photoelectrochemical sensing platforms based on different construction strategies to prevent the potenotial interference from the reducing substance and non-specific proteins existed in the actual biological samples.In addition,the sensitivity of the sensor is effectively improved through sensitization of photoactive materials.The main contents are as follows:(1)A high performance photocathodic immunosensing platform based on platinum-based nanocatalyst signal amplifier was designed.The platform adopted the p-type semiconductor bismuth acid copper(CuBi₂O₄)as cathode photocurrent signal source,and introducing platinum nanoparticles-reduction graphene oxide nanosheets(Pt-GR)complexes as signal amplifier.In this PEC system,p-type semiconductor CuBi₂O₄occurred strong coupling with the hot electrons originated from effect of surface plasmon resonance(SPR)of the gold(Au)nanoparticles and formed new composite state,which could provide relatively high and stable cathode photocurrent signal.Introducing Ab₂-Pt/GR conjugate by specific sandwich immune reaction,Pt/GR played the role of high efficiency nanocatalyst to catalyze redox reaction(ORR),which significantly enhanced the cathodic photocurrent.The photocathodic immunosensor prepared based on the Pt/GR nanocomposite as the signal amplification element possessed high sensitivity and specificity to the target.In addition,since the reaction occurred at the surface of the cathode electrode is the electron reduction reaction,the prpared immunosensor had excellent resistance to the interference of multi-component reducing species in the actual biological sample.(2)In order to prevent the interference from nonspecific protein adsorption and multi-component reducing substances in actual sample detection,a peptide-based photocathodic biosensor integrating recognition peptides and antifouling peptides was designed.Taking human chorionic gonadotropin(h CG)as the model target,the recognition peptide with the sequence of PPLRINRHILTR was anchored on the surface of CuBi₂O₄/Au photocathode.And then,antifouling peptide with the sequence of EKEKEKEPPPPC was anchored to form antifouling biological interface by the Au-S bond.The peptide-based photocathodic biosensor exhibited good anti-interference ability against nonspecific proteins and reducing species.Due to the use of recognition peptides instead of antibody probes,the biosensor possessed better sensitivity.This ingenious strategy of combining peptides provides a new perspective for the practical application of photocathodic biosensors.(3)A high-performance photoanode-enhanced photocathodic immunosensor was designed,and the photoanode and biocathode separation sensing model was cleverly combined.In this sensing system,the photoanode was the signal output source to maintain a high and stable current signal,and the biocathode modified by the antibody molecules was used to identify and capture the target antigen.The photoanode based on the g-CNQDs/TiO₂-NTs inorganic nanocomposite had good PEC performance and ensured strong and stable signal output.The biocathode constructed with Pt NPs/CNTs as the substrate effectively utilizes the ORR performance of Pt NPs and therefore had high sensitivity and stability.This photoanode-enhanced photocathodic immunosensor not only has the sensitivity of the photoanode sensor,but also can exert the excellent performance of the photocathode sensor against interference from reducing substances,with high selectivity and sensitivity...