Research On Biosensors Based On Noval Photoactive Materials

Photoelectrochemical?PEC?biosensor is a new generation of biosensors developed on the basis of electrochemical biosensors combined with photochemistry.Using the photoelectric conversion characteristics of photoactive materials,PEC biosensors monitor photocurrent signals in the detection system and thus analyze the targets.Commonly,photoactive materials and biological probes are indispensable for the core components of PEC biosensors;and appropriate signal amplification strategies are the key factors which could significantly improve the performance of biosensors.Since biological probes are specific for the recognition of targets,various targets need corresponding probes.However,photoactive materials and signal amplification strategies feature a universal flexibility.Therefore,the preparation of photoactive materials with various characteristics and the construction of signal amplification strategies are of great significance for the endeavor of PEC biosensors with high efficiency,stability and wide applicability.Based on this,some new photoactive materials with appropriate signal amplification strategies were adopted to construct a series of highly sensitive PEC biosensors for analyses of small biomolecules.1.A Highly Sensitive PEC Assay with Donor-Acceptor-Type Material as Photoactive Material and Polyaniline as Signal EnhancerIn this work,a highly sensitive PEC assay was constructed based on a donor-acceptor?D-A?-type material PTB7-Th as photoactive material and polyaniline?PANI?in-situ deposited on the surface of PTB7-Th as signal enhancer.Initially,PTB7-Th that contains an electron-rich unit as donor and an electron-deficient unit as acceptor with the easy separation of electron-hole pairs and intermolecular electron transfer provided an excellent photocurrent response.Subsequently,an input target thrombin?TB?was converted to an output single-stranded DNA by a protein converting strategy.The obtained single-stranded DNA thus triggered a rolling circle amplification?RCA?to form a tandem multi-hairpin DNA nanostructure,which could function as a skeleton for immobilizing manganese porphyrin?MnTMPyP?.In the presence of H₂O₂ and aniline,a PANI layer could be in-situ deposited onto the tandem multi-hairpin DNA nanostructure with use of MnTMPyP as catalyst,leading to a significantly enhanced photocurrent for detection of TB.The proposed PEC assay presented a wide detection range of100 fmol/L to 10 nmol/L with the limit of detection?LOD?of 34.6 fmol/L.Furthermore,the proposed strategy provides a PEC analysis method based on PTB7-Th that can significantly improve the photoelectric conversion efficiency and opens an intriguing avenue to establish low background,ultra-sensitive and highly stable analytical techniques.2.A Novel PEC Biosensor Based on Bi₂Te₃ Nanosheets and Hybridization Chain Reaction AmplificationIn the previous work,we used the organic photoactive material PTB7-Th to construct a PEC aptasensor.A large amount of organic solvent was used in the experiment,which might cause additional pollutions.So we hope to overcome the disadvantage by preparing some inorganic photoactive materials.In this work,a novel PEC biosensor based on the Bi₂Te₃nanosheets and HCR amplification was prepared for highly sensitive miRNA-21 detection.Initially,the Bi₂Te₃ nanosheets,which allow electrons to flow freely on the surfaces without losing any energy were filmed on the electrode to provide a sufficient and stable photocurrent signal.Subsequently,the target miRNA-21 and auxiliary DNA were introduced and triggered the strand displacement amplification.Then,the hybridization chain reaction?HCR?strategy further improved the analytical performance of the proposed biosensor.Finally,CdTe quantum dots?QDs?were introduced,leading to a significantly enhanced photocurrent for PEC analysis.The PEC biosensor presented a detection range of 10 fmol/L to 100 pmol/L with a limit of detection?LOD?of 3.3 fmol/L.Furthermore,the proposed PEC biosensor exhibited tremendous potentials in bioanalysis and early clinical diagnosis and provided an intriguing avenue to construct highly sensitive and stable analytical techniques.3.A Sensitive PEC Biosensor Based on Bio-Assisted Synthesis of a Novel Bi2Se3 Crystal as Photoactive MaterialIn the previous work,we peeled off the bulk Bi₂Te₃ crystal into nanosheets to construct a PEC biosensor.Bi₂Te₃ nanosheets are easy to re-stack,which might hinder the wide applications.So we hope to modify the materials by improving the preparation technique.In this work,a green and high-yield hydrothermal synthesis was realized,and based on which a hexagonal phase Bi₂Se₃ crystal was prepared using alginic acid as the stabilizer and the reducing agent.Alginic acid features a mild reducing ability and a large molecular weight and size,which could control the reaction rate and provide a strong shape guiding role in the reaction process to organize materials with special morphologies.The hexagonal phase Bi₂Se₃ crystal was thus prepared with a highly uniform particle diameter and a smooth surface.In this work,the Bi₂Se₃crystal was used as the photoactive material and PANI was used as the signal enhancer to construct a PEC biosensor for sensitive detection of miRNA-21.First,the hexagonal phase Bi₂Se₃ crystal provides an excellent photocurrent signal.Then HCR amplification is triggered under the circular involvement of the target miRNA-21 and assist DNA.Finally,PANI was deposited on the double-stranded DNA of the HCR product as a template to enhance the photocurrent signal of Bi₂Se₃.The detection range of miRNA-21 from 0.5 fmol/L to 1 pmol/L with a limit of detection?LOD?of 0.17 fmol/L were obtained by analyzing the photocurrent signals.This work has achieved satisfactory results and pointed out new research directions for the development of PEC biosensors.