| Photoelectrochemical?PEC?analysis is a new analytical method based on PEC process and chemical/biological identification process.The technique using the light as the excitation signal and the current as the detection signal has the distinct advantages of high sensitivity,quick response,simple equipment and easy miniaturization.Currently,it has been widely applied in the field of biological and environmental analysis.Under light radiation,the photoelectric layer modified on the electrode surface is excited after absorbing the photon,and the generated carriers yield the charge separation and electron transfer,thus producing the photocurrent.The specific biometric identification between the probe and the target analyte results in the change of the corresponding electrical signal.The relationship between this change and the concentration of target analytes is the basis of qualitative and quantitative analysis of PEC biosensor.Therefore,the PEC sensor in the functional structure includes two parts:the photoelectric conversion unit and the sensor identification unit.The material selection and sensor identification strategy of photoelectric layer are two key points for the construction of the PEC sensor.In this paper,the functional interface of photoelectrode sensing was constructed by using the controllable preparation of different morphological CdS-graphite-carbonized carbon?g-C3N4?heterojunction nanomaterials.Combination of the gold silver nanoparticles?Au@Ag NPs?,CuS functionalized graphene oxide nanosheet?GO-CuS?,Cu2O@Ab2 conjugate nanoprobe with the biological recognition,and in virtue of serial signal amplification technologies,such as spatial-resolved,high-throughput analysis for sensitive,accurate and high-throughput detection of the tumor markers?microRNA and Prostate-Specific Antigen,PSA?were realized.1.The exciton-plasmon interaction?EPI?signaling mechanism between the CdS@g-C3N4 nanowire heterojunction and Au@Ag NPs was introduced into PEC bioanalysis for the first time.A sensitive and accurate PEC DNA biosensor platform was constructed to detect microRNA-21 using high specificity of the DNA molecule and enzyme assisted cyclic signal amplification strategy.The photoelectrode of CdS@g-C3N4nanowires could generate an enhanced photocurrent compared with the pure CdS and g-C3N4 because of the formation of the p-n heterojunction.Due to the natural absorption overlap,the exciton of CdS@g-C3N4 and the plasmon of Au@Ag NPs could be induced simultaneously to form EPI.Specifically,the perfect overlap of the wide absorption spectrum of Au@Ag NPs with the photoluminescence spectrum of CdS@g-C3N4 allows the resonance energy transfer and EPI between CdS@g-C3N4 nanowire and Au@Ag NPs simultaneously.The effective EPI renders the signal change modulated by the interparticle distance significantly.Such a signaling mechanism was then used to construct the PEC biosensor for microRNA-21 detection,within which the duplex-specific nuclease?DSN?was further introduced to enhance the sensitivity.The constructed PEC biosensor exhibits the sub-fM level(0.05 fmol L-1)detection of microRNA-21 with a wide range from 1.0×10-16 to 1.0×10-9 mol L-1.In addition,the sensor was successfully used to detect the content of microRNA-21 in human serum samples,which was consistent with the commercial qRT-PCR test results.The relative errors between the two methods are less than 8.1%.2.A universal spatial-resolved photoelectrochemical ratiometry for prostate specific antigen?PSA?detection was designed for the first time based on dual-electrodes array modified by CdS@g-C3N4 heterojunction coupled with CuS quantum dots?QDs?as signal amplification tags.Specifically,a new kind of photoactive material,CdS@g-C3N4p-n heterojunction with highly photoelectric conversion efficiency and good chemical stability,was synthesized and immobilized on two spatial-resolved electrodes?WE1 and WE2?.After immobilizing gold nanoparticles,capturing PSA antibodies on the electrodes,WE1 incubated with various concentrations of PSA was taken as working electrode,while WE2 with fixed concentration of PSA was used as an internal reference electrode.Next,signal antibodies of PSA labeled CuS QDs as PEC signal quenchers were immobilized on the electrodes to form sandwich-type immunocomplex.With the aid of multiplexed disjunctor,the PEC responses of the dual-electrodes were recorded and PSA was quantified via the ratio values of photocurrent intensity from WE1 to WE2.Combining the fine PEC performance of CdS@g-C3N4 heterojunction with the superior quenching effect of CuS QDs in the spatial resolved platform,the ratiometric system exhibits a linear range from 1.0×10-11 to 5.0×10-8 g m L-1 with the limit of detection of4.0 pg m L-1.In addition,the method was successfully applied to the determination of human serum samples,and the results were consistent with the Xinyang central hospital.The relative errors between the two methods are less than 7.5%.3.This work reports the first demonstration of CdS@Au-g-C3N4 heterojunction signal amplification by functionalized graphene oxide-CuS@Ab2 conjugates for the state-of-the-art photoelectrochemical?PEC?bioanalysis.The enhanced photocurrent intensity from the prepared CdS@Au-g-C3N4/ITO electrode was realized as follows:?i?the Au nanoparticles?Au NPs?act as a plasmonic photosensitizer,exhibiting a localized surface plasmon resonance?LSPR?effect during the PEC process;?ii?the Au NPs serve as an electron relay,facilitating the charge transfer from g-C3N4 to CdS;?iii?the formation of the p-n heterojunction between CdS and g-C3N4 greatly increase the charge separation to improve the photoelectric conversion efficiency.Meanwhile,graphene oxide-CuS@Ab2 signal amplification tags were introduced into this system for sensitivity enhancement due to the steric hindrance effect and consumption of the electron donor.Such an ultrasensitive PEC immunosensing platform was realized for prostate specific antigen?PSA?detection with wide linear range from 1.0×10-12 to 1.0×10-8 g mL-1 and a low detection limit of 0.6 pg mL-1.The sensor was successfully applied to the analysis of human serum samples,and the results are consistent with the reference values provided by the Xinyang central hospital.The relative errors between the two methods are less than 9.1%.This work is summed up in providing a promising way for tactful design of metal-heterojunction hybrid photoactive materials to achieve highly sensitive analysis.4.A high throughput detection platform for near-simultaneous quantitation of prostate specific antigen?PSA?in human serum samples were realized based on CdS@g-C3N4p-n heterojunction modified rotatable indium tin oxide?ITO?electrode arrays.Initially,a homemade rotatable disk substrate containing eight independent electrode arrays was fabricated using for working electrodes.The immuosensor was assembled by immobilizing CdS@g-C3N4 photoactive matrix,gold nanoparticles?Au NPs?,capture PSA antibodies?Ab1?,BSA,a series of concentration of target PSA,and Cu2O labeled signal antibodies?Cu2O@Ab2?on the electrode arrays.Secondly,the photoelectrochemical?PEC?signals from the electrode arrays were sequentially recorded via light site-select.Based on the above principle,rapid and sensitive detection of PSA from different biosamples were realized.This proposed immunosensor shows wide linear range from 1.0×10-11 to 5.0×10-8 g m L-1 with the detection limit of 5.0 pg m L-1.The sensor was successfully applied to the analysis of human serum samples,and the results are consistent with the reference values provided by the central hospital.The relative errors between the two methods are less than 8.3%.This work provides an insight into the exploitation of the high throughput detection platform for rapid,sensitive,portable and cost-effective bioassay. |
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