Research On The Construction Of Electrochemical Biosensors Based On Gold/ferroferric Oxide Magnetic Nanocomposite Materials

As an important branch of the sensors,electrochemical sensor is one of the most important research areas in modern analytical science due to its simple operation,easy to miniaturization,low cost,excellent selectivity,high sensitivity and good stability.Electrochemical sensor has been widely used in many fields,such as drug analysis and environmental monitoring.Nanomaterials possess many remarkable physical and chemical properties.It has the advantages of high specific surface area,thermal stability,good electron conduction and mechanical properties.In recent years,combining the properties of nanomaterials with electroanalytical techniques has opened up an emerging field in which a large number of nanomaterials can be synthesized as electrochemical sensor modifiers.Metal nanomaterials refer to metal materials whose spatial dimensions are at least one dimension to meet the nanometer level,or which are composed of these nanomaterials.Gold nanoparticles?AuNPs?have large specific surface area,good surface activity and biocompatibility,and it is easily to combined with biomolecules containing sulfhydryl groups?-SH?or amino groups?-NH₂?in the form of chemical bonds,which are often used in electrochemistry.Used as a probe carrier and signal molecule.Nano-metal oxide is a kind of nano-material with great potential,and has the characteristics of low cost,large specific surface area,wide energy band gap and good catalytic performance.Fe₃O₄ nanoparticles?Fe₃O₄NPs?are widely used in the field of electrochemistry because of their magnetic properties,good biocompatibility,low toxicity,simple preparation and strong adsorption capacity.A nucleic acid probe refers to a nucleic acid molecule DNA or RNA immobilized on a surface of a electrode as a recognition probe to specifically bind to a target molecule.The nucleic acid probe is combined with an electrochemical sensor to construct an electrochemical biosensor in the fields of disease diagnosis,drug analysis and environmental monitoring.Such as the specific detection of DNA sequences,adenosine triphosphate and other in vivo signal molecules and heavy metal ions.The work of this paper is devoted to the construction of electrochemical biosensors and their specific detection of biomolecules by combination of the magnetic glassy carbon electrodes that be modified ferroferric oxide/gold magnetic nanocomposites?Fe₃O₄@AuNPs?and nucleic acid probes.The main content is divided into the effect following four parts:1.Synthesis and characterization of Fe₃O₄@AuNPsIn this work,Fe₃O₄NPs were synthesized by solvothermal synthesis,and then Fe3O4@AuNPs was synthesized by reduction of chloroauric acid by sodium borohydride?NaBH₄?.The morphology and chemical composition of the synthesized materials were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and UV-vis spectra.It was proved that Fe₃O₄@AuNPs was successfully synthesized.2.Electrochemical detection of adenosine triphosphate by electrochemical biosensor based on nucleic acid aptamer and Fe₃O₄@AuNPs magnetic nanocompositesOn the basis of the first work,the aptamer/Fe₃O₄@AuNPs magnetic nanocomposites were obtained by self-assembly of adenosine triphosphate?ATP?nucleic acid aptamers on Fe₃O₄@AuNPs,and using aptamer/Fe₃O₄@The magnetic properties of AuNPs were modified onto a magnetic glassy carbon electrode,and the electrochemical detection of ATP was carried out using methylene blue?MB?as an indicator.The linear response range is 5×10^-92×10^-6 mol/L.The detection limit was0.42 nmol/L.This experiment demonstrates that the electrochemical biosensor constructed by aptamer/Fe₃O₄@AuNPs magnetic nanocomposites has good anti-interference ability and can be used for actual sample detection of ATP.3.Based on single-stranded DNA modified magnetic composite nanomaterial electrochemical impedance method to detect specific DNA sequencesIn this work,a DNA electrochemical sensor was constructed,and the magnetic nanocomposite Fe₃O₄@AuNPs was applied to the DNA sensor.We self-assembled a single-stranded DNA?ssDNA?probe with a thiol group?-SH?on the surface of the synthesized Fe₃O₄@AuNPs to obtain a ssDNA/Fe₃O₄@AuNPs nanocomposite,which was magnetically immobilized on the surface of the magnetic glassy carbon electrode.Compared with the conventional immobilization of the ssDNA probe on the gold electrode,the above scheme increases the specific surface area of the electrode and greatly shortens the time for the ssDNA probe to be immobilized on the electrode surface.The specific DNA sequence was specifically detected by the electrochemical impedance method?EIS?using a DNA sensor constructed.The linear response range is10^-910^-6 mol/L.The detection limit was 3.2×10^-10 mol/L.The electrochemical biosensor has a good effect on the detection of specific DNA sequences in actual human serum samples,and has a good application prospect.4.Detection of methylase activity by electrochemical biosensor constructed by DNA modified magnetic composite nanomaterial Fe₃O₄@AuNPs.In this work,an electrochemical biosensor was constructed,and the magnetic composite nanoparticle Fe₃O₄@AuNPs was applied to the sensor.We self-assembled a single-stranded DNA?ssDNA?S₁ with thiol?-SH?on the surface of synthetic Fe₃O₄@AuNPs,and hybridized S₁ with its complementary single-stranded DNA S₂ to obtain dsDNA/Fe₃O₄@AuNPs and utilized its magnetic properties.It was attached to the surface of a magnetic glassy carbon electrode?MGCE?.Compared with the conventional dsDNA probe immobilized on the gold electrode,the above scheme increases the specific surface area of the electrode while greatly shortening the time for the dsDNA probe to be immobilized on the electrode surface.The electrochemical biosensor was combined with restriction endonuclease HpaII to detect methylase?MTase?activity by square wave voltammetry using MB as an indicator.The linear response range is 0.05¹00 U/mL.The detection limit was 0.24 U/mL.In human serum samples,the sensor has a good effect in detecting the activity of MTase,indicating that the sensor has potential applications to help screen methylase inhibitors.