Study On The Detection Of Heavy Metals In Dairy Products By Electrochemical Aptasensors Based On Metal Organic Frame Materials

In recent years,the electrochemical sensor analysis technology has been breakthrough,which is due to the explosion of nanotechnology and biotechnology.Electrochemical biosensor analysis technology has the advantages of high sensitivity,low cost,simple and fast,high selectivity and specificity,and plays an indispensable role in trace and trace analysis.The method of electrochemical biosensor analysis and detection is simple and fast,which has always been concerned by researchers.By combining nano-materials with electrochemical biosensors and using the properties of nano-materials,the sensitivity of the sensors can be improved,the detection time can be shortened,and the physicochemical properties of the sensors can be further stabilized.It is dedicated to research and construct the analytical and detection technology of electrochemical biosensor based on nanometer material sensitization,and apply this technology to the safety inspection and quality monitoring of dairy products,so as to combine the technology with the actual practice,and use the technology to make the consumer’s health secure enough,and indirectly promote the development of dairy industry.In this paper,three different electrochemical DNA sensors were constructed and applied to trace detection of Hg²⁺,Ag⁺and Pb²⁺in dairy products.The specific contents are:Part 1.Electrochemical aptasensor for Hg²⁺determination based on Functionalized nanocomposites with the AuNFsIn this work,a sensitive and selective electrochemical biosensor for the detection of mercury ions(Hg²⁺)has been researched based on specific reaction of the T-Hg²⁺-Tand Au Nanoflowers（AuNFs）nanoparticles.The thiol modified T-rich DNA probe was immobilized in AuNFs modified electrode through Au-S bond.When the Hg²⁺was captured by T bases,the DNA chain structure was inflected and the methylene blue（MB）that label at DNA probe 3’distal terminus close to electrode surface.As a result,the signals of the detection were amplification.Taking advantage of the amplification effect,the electrochemical biosensor detection of Hg²⁺in the range of 1 fM 1 nM,with a detection limit is 0.39 fM which is lower than the maximum contamination.Meanwhile,the biosensor provided unexceptionable selectivity for Hg²⁺against other heavy ions.Furthermore,the proposed biosenser had a tremendous potential for the application of Hg²⁺detection in future.Part 2.Electrochemical detection of Ag⁺in dairy products by using metal organic frame functional materials as Bionic enzymeIn this work,a highly sensitive electrochemical DNA biosensor for Ag⁺detection made of the rigid structures of porphyrinic MOFs（PorMOFs）and colloidal gold nanoparticles（AuNPs）.In the presence of Ag⁺,with the interaction of cytosine-Ag⁺-cytosine（C-Ag⁺-C）,DNA sequence labeled with PorMOFs near 5′end immobilized onto the surface of AuNPs has a self-hybridization and then forms a duplex like structure which makes PorMOFs approach the electrode.In consequence,Ag⁺detection could be quantitative in range of 10^-13 to 10^-6 M with a low detection limit of0.016 pM.Meanwhile,the biosensor display batter stability and selectivity.Part 3.Electrochemical detection of Pb²⁺in dairy products by using metal organic frame functional materials as Bionic enzymeA highly sensitive electrochemical detection method for lead ions(Pb²⁺)was developedbased on a DNA functionalized iron-porphyrinic metal-organic framework（DNA2/AuNPs-FeTCPP@MOF）as a probe.The resulting FeTCPP@MOF composites can mimetically catalyze the oxidation of ophenylenediamine（o-PD）to2,2′-diaminoazobenzene,which is a good electrochemical indicator for signal readout.In the presence of Pb²⁺,DNA1 could be specifically cleaved at the ribonucleotide（rA）site,which produced the short DNA1 fragment to hybridize with DNA2 which was linked to AuNPs-FeTCPP@MOF immobilized on the surface of carbon electrode.The“signal-on”electrochemical sensor can detect Pb²⁺down to 0.36 fM with the linear range of 1 pM to 100 nM.The prepared electrochemical sensor exhibited the advantages of low-cost,simple fabrication,high sensitivity and selectivity.