Study On Photoelectrochemical Biosensor Based On Semiconductor Nanomaterials Enhanced By Various Sensitizers And Nucleic Acid Signal Amplification

At present,the simple,rapid and sensitive biomolecular analysis method is one of the most important and popular research topics in analytical chemistry,which has attracted great research interest in the fields of disease diagnosis,environmental monitoring,drug analysis,food safety analysis,life analysis and pathogenic microorganism research.Photoelectrochemistry?PEC?assay is a new analytical method developed after optics,photochemistry and electrochemistry.The PEC assay has been highly concerned and extensively studied owing to the significant advantages of simple,high efficiency,low background signal,high sensitivity and good stability.During the development of PEC biosensors,screening photoelectric materials with good performance,combining high efficiency signal ampli fication strategies,introducing specific molecular recognition elements,developing novel and practical analysis methods are of great significance for improving the analytical performances of PEC biosensors and achieving high sensitivity detection of biomolecules.PEC biosensors with simple operation,excellent performance and broad application prospects have been constructed based on semiconductor nanomaterials enhanced by various sensitizers and nucleic acid signal amplification techniques.The details are mainly as follows:1.An ultrasensitive‘‘on-off-on''photoelectrochemical aptasensor based on signal amplification of a fullerene/CdTe quantum dots sensitized structure and efficient quenching by manganese porphyrinPEC assay as a newly emerging and vibrantly developing analytical technique has attracted great research interests in sensitive detection of various analytes because of its desirable merits over traditional optical and electrochemical techniques.However,challenges still existed for improving its sensitivity and extending its applications.Herein,combination of narrow band gap CdTe quantum dots?QDs?and wide band gap nano-C₆₀to form a sensitized structure could obtain a desirable initial PEC signal.The introduction of manganese porphyrin?MnPP?could achieve the efficient signal quenching toward nano-C₆₀@CdTe QDs sensitized structure,therefrom reducing the background signal for improvement of the detection sensitivity.Based on the signal amplification of nano-C₆₀@CdTe QDs sensitized structure and efficient signal quenching of nano-C₆₀@CdTe QDs by MnPP,an ultrasensitive“on-off-on”PEC aptasensor was proposed.With thrombin?TB?as a target model,this ultrasensitive PEC aptasensor showed a wide linear range from 1.0 fmol/L to 10 nmol/L with a low detection limit of 0.3 fmol/L.This intriguing PEC platform could be considered as a versatile template for accurate and ultrasensitive estimation of various kinds of biomarkers,heavy metal ions and cells also.2.Zirconium-based metal-organic framework sensitized by thioflavine-T for sensitive photoelectrochemical detection of C-reactive proteinThe zirconium-based metal-organic framework?PCN-777?possesses an energy band width of 3.67 eV,which greatly limits its PEC performances,especially its photo-current conversion efficiency.Herein,the combination of narrow band gap thioflavine-T?Th-T?and PCN-777 forms a sensitized structure,which can promote the electron transmission and inhibit the recombination of electrons and holes,thus significantly improving the photo-current conversion efficiency.A novel PEC assay was developed for sensitive detection of c-reactive protein?CRP?based on PCN-777 as the photoelectric material and Th-T as the effective signal sensitizer coupled with rolling circle amplification?RCA?.Briefly,the synthesized PCN-777 with a homogeneous octahedron was firstly coated on the electrode surface,thereby providing an initial PEC response.Subsequently,target?CRP?was converted into primer strand via a simple protein converting procedure,and thus the obtained primer strand could trigger RCA on the sensing interface for generating abundant G-rich sequence,which would specifically bind with Th-T to form numerous steady G-quadruplex structure.The introduction of Th-T could result in a significantly enhanced PEC response for the quantitative detection of CRP.The designed PEC sensing for CRP assay exhibited a linear range of 50 fmol/L to50 nmol/L with a detection limit of 16 fmol/L.More importantly,the designed strategy offered a novel PEC analytical approach for sensitive detection of biomarkers in disease diagnosis,treatment monitoring and prognosis assessment.3.Using p-type PbS quantum dots to quench photocurrent of fullerene-Au NP@MoS₂ composite structure for ultrasensitive photoelectrochemical detection of ATPThe conventional sensitized structure formed by modifying photoelectric materials and sensitizers layer by layer can improve photo-current conversion efficiency to some extent.However,these photoelectric materials and sensitizers exist independently,which leads to long electron transfer path,large energy loss and limited PEC signal enhancement.In this work,fullerene(C₆₀)-decorated Au nanoparticle@MoS₂(C₆₀-Au NP@MoS₂)composite material was prepared through Au-S bond,and it could shorten electron transfer path,reduce energy loss and significantly improve photo-current conversion efficiency,leading to a desirable PEC signal.Herein,a“signal-off”photoelectrochemical?PEC?biosensor was designed for ultrasensitive adenosine triphosphate?ATP?detection based on C₆₀-Au NP@MoS₂ composite material as a signal indicator and a p-type PbS quantum dot?QD?as an efficient signal quencher.In the presence of p-type PbS QDs,the PEC signal of n-type C₆₀-Au NP@MoS₂ was effectively quenched because p-type PbS QDs could compete with C₆₀-Au NP@MoS₂ to consume light energy and electron donor.Besides,the conversion of a limited amount of target ATP into an amplified output PbS QD-labeled short DNA sequence?output S1?was achieved via target-mediated aptazyme cycling amplification strategy,facilitating ultrasensitive ATP detection.The proposed signal-off PEC strategy exhibited a wide linear range from 1.00×10^-2 pmol/L to 100nmol/L with a low detection limit of 3.30 fmol/L.Importantly,this proposed strategy provides a promising platform to detect ATP at ultralow levels and has potential applications,including diagnosis of ATP-related diseases,monitoring of diseases progression and evaluation of prognosis.4.CdTe QD-CeO₂ complex as a strong photoelectrochemical signal indicator for the ultrasensitive microRNA assayThe photoelectrochemical?PEC?signal can be enhanced by constructing sensitization structures containing photoactive materials and appropriate sensitizers.However,usually,the photoactive materials and sensitizers were separated in independent nanostructures,thereby producing long electron transfer path and large energy loss,which could further result in limited photo-current conversion efficiency and PEC signals.Herein,we designed a novel sensitization nanostructure simultaneously containing the photoactive material cerium dioxide?CeO₂?and its sensitizer CdTe quantum dots?QDs?as the strong PEC signal indicator?CdTe QD-CeO₂ complex?,which prominently enhanced photo-current conversion efficiency because of the shortened electron transfer path and reduced energy loss.The proposed CdTe QD-CeO₂ complex was used to construct a PEC biosensor for achieving ultrasensitive determination of microRNA-141?miRNA-141?coupling with target converting amplification and DNA supersandwich structure amplification.The designed PEC biosensor demonstrated a wide linear range from 0.5 fmol/L to 5 nmol/L with a detection limit of 0.17 fmol/L for miRNA-141.Impressively,this work provided a new and strong PEC signal indicator for the construction of PEC sensing platform and would extend the application of PEC sensors in bioanalysis and early disease diagnosis.5.Ultrasensitive photoelectrochemical biosensor based on DNA tetrahedron as nanocarrier for efficient immobilization of CdTe QDs-methylene blue as signal probe with near-zero background noiseUsually,photoelectrochemical?PEC?assays were devoted to the direct modification of photoactive materials on sensing interface,thereby producing high initial signal and unneglected background noise,which could further result in low sensitivity and restricted detection limit during the detection of targets.In this work,DNA tetrahedron?TET?was used as the nanocarrier to immobilize the photoactive material CdTe quantum dots?QDs?and its signal enhancer methylene blue?MB?,and the formed TET-QDs-MB complex with excellent photoelectric characteristics was considered as an effective PEC signal probe,thus avoiding direct modification of photoactive material on sensing interface and producing a near-zero background noise to improve the detection sensitivity.Based on the TET-QDs-MB complex as PEC signal probe and the duplex specific nuclease?DSN?enzyme-assisted target cycling amplification strategy,a PEC biosensor with near-zero background noise was established for ultrasensitive microRNA-141?miRNA-141?detection.The proposed PEC biosensor performs a wide linear range with a low detection limit of 17 amol/L for miRNA-141,paving a new and promising horizon for highly accurate and ultrasensitive monitoring of multifarious analytes such as proteins,DNAs and miRNAs in bioanalysis and disease diagnosis.6.Ultrasensitive photoelectrochemical assay with PTB7-Th/CdTe QDs sensitized structure as signal tag and 4-CD precipitate as efficient quencherConventional PEC sensors require the addition of electron donors in electrolyte solution to maintain the continuity of electron transmission.However,the separation between electron donor and photoelectric material would seriously affect the electronic supply,transmission efficiency and detection accuracy.In this study,the donor-acceptor photoelectric material poly{4,8-bis[5-?2-ethylhexyl?thiophen-2-yl]benzo[1,2-b:4,5-b?]dithiophene-2,6-diyl-alt-3-fluoro-2-[?2-ethylhexyl?-carbonyl]thieno[3,4-b]thiophene-4,6-diyl}?PTB7-Th?and its sensitizer CdTe QDs were continuously drip-coated on the electrode surface,and the resulted PTB7-Th/CdTe QDs sensitized structure could generate a strong initial PEC signal without any additional electron donors.Herein,an ultrasensitive PEC assay was developed for the monitoring of microRNA-141?miRNA-141?based on PTB7-Th/CdTe QDs sensitized structure as signal tag and the benzo-4-chloro-hexadienone?4-CD?precipitate as efficient quencher.The 4-CD precipitate on sensing interface could efficiently block electron transfer,leading to a significantly quenched PEC signal for determination of miRNA-141.The designed PEC biosensor performed a wide detection range from 0.1 fmol/L to 1 nmol/L with a low detection limit of 33 amol/L for miRNA-141,which paved a new avenue for highly accurate and ultrasensitive monitoring of multifarious analytes in bioanalysis and clinical diagnosis.