Construction Of Electrochemical Biosensor Interface Based On PCOFs Nanocomposite And Study On Aβ42 Analysis And Detection

Amyloidβ-protein（Aβ）is one of the important mechanisms leading to the occurrence and development of Alzheimer Disease（AD）.Aβoligomer（AβO）is considered to be one of the main pathogenic factors of AD,and its expression level is closely related to the occurrence and development of AD.Therefore,the high selectivity and sensitivity of AβO detection under physiological conditions is very important for the early clinical diagnosis and intervention treatment of AD.Electrochemical sensor has the characteristics of simple operation,low cost,fast sensitivity and so on.Covalent Organic Frameworks（COFs）are often used to enrich the tested materials and serve as effective reaction carriers in electrochemical biosensing.Porphyrins are planar rigid molecules with largeπ-electron conjugated plane structure and excellent photoelectric activity.They are ideal functional monomers for preparing high performance COFs.This paper mainly through the design of porphyrin-based covalent organic framework materials（pCOFs）,which has both the inherent characteristics of COFs and porphyrin compounds,in enhancing the electrochemical biosensor interface conductivity at the same time can improve its biocompatibility,through the method of synthetic modification,loading gold nanoparticles,the development of high performance electrode modified composite materials.Combined with AβO recognition unit,electrochemical biosensors with high sensitivity and rapid detection of AβO were constructed.The main contents are as follows:1)pCOFs were prepared by solvothermal method using 5,10,15,20-tetra（4-aminophenyl）-21H,23H-porphyrin（TAPP）and2,5-dihydroxy-1,4-phenyl dicarboxylaldehyde（DHTA）as organic ligands,followed by post-synthetic modification.The Au@pCOFs composite material was obtained by loading gold nanoparticles on pCOFs using Na BH₄ reduction of chlorauric acid.The pCOFs and Au@pCOFs composites were characterized by transmission electron microscopy,X-ray diffraction analyzer,X-ray photoelectron spectroscopy,Fourier transform infrared spectrometer and other characterization methods.The Au@pCOFs nanocomposite material was modified on the electrode surface,and then Pr P^C protein was fixed on the surface of the sensor interface through Au-S bonding.Finally,AβO was captured by the specific interaction between Pr P^Cprotein and AβO.Based on the oxidation current generated by Au@pCOFs catalytic oxidation of potassium ferricyanide（K₃[Fe（CN）₆]）as an electrochemical signal,the performance of the prepared electrochemical biosensor system was evaluated by electrochemical methods such as cyclic voltammetry,AC impedance and differential pulse voltammetry.The results show that the prepared AβO electrochemical biosensor has good electrochemical performance.The linear range of the sensor was 1 n M to 700 n M with a detection limit was 0.87 n M,and also shows good specificity,anti-interference ability and stability.2)In order to overcome the shortcomings of traditional electrochemical biosensors with single electrical signal output,A ratio electrochemical sensor system was constructed on the basis of the prepared AβO electrochemical biosensor.By clicking chemical reaction,the acetylene COFs and azide-modified aptamer（N₃-Apt）were combined,and then the signal molecule methylene blue（MB）was adsorbed by electrostatic interaction,and the MB@Apt-COF biological coupling was synthesized.MB@Apt-COF is fixed to the constructed single signal electrochemical sensor through the specific mutual recognition of N₃-Apt and AβO.The ratio electrochemical biosensor system was constructed by using Au@pCOFs catalyzed K₃[Fe（CN）₆]oxidation signal and MB signal probe as electrochemical signals for the highly sensitive detection of AβO.The ratio sensor showed excellent analytical performance with a linear range of 10 p M to 1μM and a detection limit of 5.1 p M.In addition,the ratio sensor had good reproducibility,stability and selectivity,and had been successfully applied to detect AβO in real CSF samples.