Study On Electrochemical Biosensors Sensitized With Nanomaterials And Their Applications In Dairy Analysis

Electrochemical biosensing analysis method with the advantages of high selectivity,good specificity,high sensitivity,low cost,simple and fast has becoming a kind of commonly used test methods in trace and trace analysis.In recent years,with the rapid development of nanotechnology and biotechnology,the wide employment of nanomaterials provides a new research direction for the development of new sensitive electrochemical biosensing applications analysis system.Electrochemical biosensors Based on nanomaterials sensitization,not only in terms of detection performance is improved,and its chemical physical properties,as well as the detection sensitivity and detection time have been increased and improved on the basis of the original.Research and development of electrochemical biosensor based on nanomaterials sensitization for dairy product safety and quality test,are not only having the guarantee to the dairy product safety and quality,but also having great realistic significance for the development of dairy industry and the health of the masses.In this paper,based on different types of nanomaterials,three different kinds of electrochemical biosensors were developed and used to trace detection of different substances in real samples.The electrochemical biological sensing method builded in this paper has excellent electrochemical performance,which provides a theoretical and technical supporting for improving the analysis and research methods to safety and quality in different form dairy analysis.The specific contents are: Part 1.Functionalized nanocomposites with the optimal graphene oxide/Au ratio for amplified immunoassay of E.coli to estimate quality deterioration in dairy productAn amplified electrochemical immunosensor was developed by exploiting poly?diallyldimethylammonium chloride?-functionalized graphene oxide and gold nanoparticles?GO-PDDA@AuNP?as sensing platform.Highlight of this work was to investigate and optimize the ratio of GO-PDDA to AuNP for sensitivity enhancement.The suitable GO-PDDA@AuNP nanocomposites were proven to not only provide an excellent biocompatible microenvironment for the immobilized antibody,but also accelerate electron transfer to enhance electrochemical signal.Moreover,the {dAb-Au-THi} nanoprobes as biorecognition elements were designed by utilizing the amplification effect of AuNPs to load detection antibody?dAb?and enormous thionine?THi?,in which d Ab was used for specific recognition of E.coli and THi served as electroactive species.Under optimal conditions,experimental results demonstrated that the variations??I?in the peak current linearly depended on the logarithmic value of E.coli concentration from 50 to 5.0×10⁶ cfu mL–1 with the detection limit of 35 cfu m L–1.Recovery experiments were also performed for E.coli assay in dairy product?pure fresh milk,yogurt in shelf-life and expired yogurt?,and the recoveries of standard additions were in the range of 89.7%¹12.6%.The excellent performance of the proposed strategy indicated its promising prospect as a valuable tool to estimate the quality deterioration in dairy product.Part 2.Electrochemical sensor for sensitive monitoring of mercury ion in dairy product based on aromatic carboxylic metal-organic framework as a biomimetic catalystAn amplified electrochemical aptasensor for the determination of mercury ions(Hg²⁺)has been developed based on graphene oxide/gold nanoparticles?GO@Au?nanocomposites which were prepared by hydrothermal method for constructing sensing platform.Highlight of this work was to using NH₂-BDC?Cu?-MOF as a catalyst to catalyze glucose realizing enzyme-free signal amplification.Primarily,the GO@Au nanocomposites as signal amplification elements were dropped onto the electrode.Thereafter,the thiolated capture DNA probe?CP?was immobilized on the GO@Au nanocomposites modified electrode via the S-Au bond.With the addition of Hg²⁺ and the thiolated signal DNA probe/Au NPs/NH₂-BDC?Cu?-MOF?SP/Au NPs/NH₂-BDC?Cu?-MOF?,the functionalized SP/Au NPs/NH₂-BDC?Cu?-MOF were fixed onto the electrode surface by the formation of T-Hg²⁺-T complex and catalyzed the oxidation of glucose when the existence of glucose in the detection solution.Under the optimal conditions,the results of the proposed aptasensor illustrated that the peak current was linear with the logarithmic value of Hg²⁺ concentration from 0.1 aM to 100 nM with the low detection limit of 0.18 aM?S/N = 3?.Furthermore,the electrochemical aptasensor showed high selectivity towards Hg²⁺ and repeatability.The developed aptasensor were applicable for the quantitative determination of Hg²⁺ ions in real samples.Part 3.Electrochemical aptasensor for Mg²⁺ determination based on Au/MMPF-6?Fe?simulation of the catalytic hydroxylamineThe preparation of Au NP/MMPF-6?Fe?nanocomposites was gold nanoparticles?Au NPs?and metal porphyrin framework ganging together through static adsorption.Au NP/MMPF-6?Fe?nanocomposites were characterized by using transmission electron microscope?TEM?,electrochemical impedance spectroscopy?EIS?and voltammetry.MMPF-6?Fe?showed a pair of redox peaks of the Fe?III?TCPP/Fe?II?TCPP redox couple.The AuNPs/MMPF-6?Fe?-based electrochemical sensor demonstrates a distinctly higher electrocatalytic response to the oxidation of hydroxylamine due to the synergic effect of the gold metal nanoparticles?Au NPs?and metal-metalloporphyrin matrix.Electrochemical sensor based on HP/Au NP/MMPF-6?Fe?nanoprobe as the catalyst of hydroxylamine generating signals,was used for the fast quantitative detection of Mg²⁺ in the dairy.Experimental results show that under optimized conditions the peak current?I?and the logarithmic value of Mg²⁺ concentration on numerical rang from 0.01 to 50.0 mM had a good linear relationship,the detection limit is 3 ?M.Standard addition recovery experiments also analyze the Mg²⁺ in dairy,and the recoveries were between 90.7% and 109.2%.The developed strategy with excellent performance of high reproducibility and stability,suggesting the potential being an effective tool for evaluating the quality change of dairy products.Moreover,our work is not only providing a simple method to realize direct electrochemical behaviour of metal porphyrins,also expanding the application prospect of metal organic framework composites in terms of biological analysis.