Construction And Application Of Optical/Electrical Biosensors Based On Functional Polymer Materials

This thesis aims to explore new application value of functional polymer materials in the field of biosensor with tumor markers as the analysis object,and develops the photoelectric,fluorescence,and porous characteristics of graphite phase carbon nitride and metal organic framework materials for constructing series of optical/electrical biosensors on the basis of the transduction between biometric signals and optical/electrical signals.These biosensors are designed for solving the problems containing insufficient detection modes,low utilization of sensing interface,cumbersome detection equipment and insufficient development of functional polymer material.These biosensor involve the exploitation of original sensing modes,the design of portable 3D printing detection devices,the application of multiple signal enhancement modes and the construction of different biosensing interfaces.The main contents are listed as follows:In chapter 1,the concept,classification and detection significance of tumor markers were briefly introduced.Then the classification,principle and signal amplification modes of optical/electrical biosensors were summarized,followed by their application in tumor marker detections.Furthermore,the synthesis methods of porous coordination polymer（metal-organic framework）materials and conjugated polymer material（g-C₃N₄）were introduced.Finally,the purpose and main content of this paper were summarized.In chapter 2,F8BT/g-C₃N₄heterojunction and the local surface plasmon resonance（LSPR）of Au NPs were combined to develop a portable 3D printing photochemical（PEC）detection mode for the detection of carcinoembryonic antigen（CEA）.The photoelectrochemical biosensor was divided into 3 functional modules.The biometric module could accomplish the CEA recognition and signal enhancement function.The target CEA was anchored on the interface of magnetic bead by the recognition mechanism of CEA and its aptamer to trigger the roll-ring amplification（RCA）reaction.Numerous functional DNA fragments（S-DNA）were released by exonuclease III（Exo III）.The interface sensing module could realize the signal transduction function.The F8BT/g-C₃N₄heterojunction and the LSPR effect of Au NPs were combined by constructing a photoelectric sensing interface through biological assembly with DNA-Au NP probes to enhance photocurrent.After adding the released S-DNA,the DNA-Au NP signal probes were detached from the surface of F8BT/g-C₃N₄,weakening the LSPR effect of Au NP on the sensing interface and decreasing the photocurrent.The photoelectric detection module was composed of a designed 3D printing device and an electrochemical workstation to complete the detection and output the photoelectric signals.The functional modules constituting the sensor had their own attributes and were connected to each other for highly sensitive detection of CEA.The detection range of CEA was 0.02 ng m L^-1～50 ng m L^-1,and the detection of limit was 6.7 pg m L^-1.In chapter 3,CQDs/g-C₃N₄heterojunction nanocomposite was applied as the main component of the photoelectric sensing interface in the ratio-based PEC biosensor.The dual-channel electrode was used to set the built-in self-calibration unit to overcome the fluctuation of the photocurrents caused by the changes of the external environment.The steric hindrance effect,generated by the combination of the alpha-fetoprotein（AFP）and its aptamer,could hinder the electron transfer between CQDs/g-C₃N₄and the electron donor（ascorbic acid）in the electrolyte.Finally,the obtained photocurrent ratio（I_c/I_w）between the internal correction area and the working electrode area of the dual-channel electrode were carried out for quantitative analysis of AFP.The linear detection range of AFP in the designed 3D printing detection device was 2 ng m L^-1～500 ng m L^-1,and the detection limit was 0.65 ng m L^-1.In chapter 4,in view of Na YF₄:Yb,Tm@ZIF-8-derived Na YF₄:Yb,Tm@Zn O as photosensitive materials,with the assistant of DNA walker driven by Exonuclease III（Exo III）for amplification strategy,the portable photoelectrochemical（PEC）biosensing on designed 3D printing device was constructed for carcinoembryonic antigen（CEA）detection.Under the excitation of 980 nm near-infrared light（NIR）,the light conversion of Na YF₄:Yb,Tm@Zn O were divided into two processes,which contained the Na YF₄:Yb,Tm converting the NIR into visible and ultraviolet,as well as Zn O in situ absorbed the light for photocurrent generation.Under the recognition mechanism of the target CEA and its aptamer,the DNA walker was driven by Exo III and performed mechanical movement on 3D DNA track,releasing many G bases to enhance the photocurrent of Na YF₄:Yb,Tm@Zn O for quantification analysis of CEA.The linear analysis range of this PEC biosensor for CEA was 0.1 ng m L^-1～300 ng m L^-1,and the detection limit was 0.032 ng m L^-1.In chapter 5,a visual fluorescent biosensor was designed for the detection of tumor markers with the paper-based NH₂-MIL-125（Ti）sensing interface constructed by impregnation modification.NH₂-MIL-125（Ti）was synthesized by a simple solvothermal method.Taking carcinoembryonic antigen（CEA）as an example,the GDH-Au NP-Ab₂probe was introduced by the recognition between CEA and its antibody.The glutamate dehydrogenase（GDH）loaded on the surface of Au NP catalyzed sodium glutamate to produce humid ammonia gas which reacted with paper-based NH₂-MIL-125（Ti）by the static headspace method,then the color of paper-based NH₂-MIL-125（Ti）turned from yellow to white with the increased fluorescence under ultraviolet light at the same time.The CEA detection range of this fluorescent biosensor was 100 pg m L^-1～200 ng m L^-1,and the detection of limit was41 pg m L^-1.With the assistance of visualization method and fluorescence method,this biosensor realized the dual-signal detection of CEA and further expanded the application range of MOFs in tumor marker detection.In chapter 6,a gas-sensitive electrochemical biosensor was constructed to analyze alpha-fetoprotein（AFP）based on the porosity characteristic of ZIF-67molecular sieve.Aiming at the problems of cumbersome procedures in interface assembly process of the electrochemical biosensor and low utilization of the sensing interface,the design was based on the hydrogen-mediated signal transduction process between biometric signal and electrical signal.Using the Ab₂@Pt NP probe labeled with platinum nanoparticles（Pt NP）as a link,the AFP immune response was linked to the catalytic reaction between Pt NP and ammonia borane for hydrogen production.The Pd nanowire sensing layer supporting on the surface of gold interdigital electrode formed Pd Hx with the generated hydrogen gas and generated current response.The oxygen in the air affected the formation of Pd Hx,making the low current response under low concentration AFP condition.ZIF-67 with a window size of 0.331 nm was molecular sieve layer of the gas-sensitive sensing interface,which could pass hydrogen（kinetic diameter of 0.289 nm）and isolate oxygen（kinetic diameter of0.346 nm）during the detection process to reduce the influence of oxygen for improving the sensitivity and efficiency.This sensing mode improved utilization of sensing interface,and the detection limit for AFP was 0.04 ng m L^-1.