Construction Of Amperometric Biosensors Based On Nanocomposite And Research On Heavy Metal Ions Detection

Amperometric enzymatic biosensor is a kind of electrochemical sensor with current as output signal.It has been widely concerned for its simple fabrication,fast detection speed,high accuracy,high sensitivity and low detection limit,which has attracted extensive attention of relevant scholars.Nanocomposites are prepared by combining the advantages of nanomaterials and other materials.They have the advantages of large specific surface area,strong catalytic ability and good biocompatibility,so they have broad prospects in the field of biosensing.Heavy metal ions(HM)do serious harm to human health and living environment,and the sensitive detection of HM have important scientific significance and application value.In this thesis,we briefly discussed the determination of enzyme activity,the construction of enzyme biosensor and the quantitative analysis of HM.At the same time,we applied nanocomposites with large specific surface area and good biocompatibility to biosensor research.Enzyme modified electrodes were constructed by immobilizing enzyme on metal organic frameworks(MOFs)and transition metal sulfide nanoparticles,respectively.The main research contents are as follows:1.Based on the inhibitory effect of Hg²⁺and Ag⁺on the enzymatic activity of glucose oxidase(GOx),we used the internally calibrated electrochemical continuous enzyme assay(ICECEA)platform to detect HM for the first time,and realized the quantitative tracking detection of enzyme activity changes during the inhibition process.And the GOx-Pt NPs complex was also used to quantitatively analyze Hg²⁺and Ag⁺.The results show that the limit of detection(LOD,3?/s)of GOx-Pt NPs to Hg²⁺is 2.0 n M,the linear range is 0.02?5.0?M and 5.0?45.0?M;the LOD of GOx-Pt NPs to Ag⁺is 0.02 n M,the linear range is 0.2?60.0 n M and60.0?200.0 n M.Therefore,the ICECEA platform has the advantages of low detection limit,high sensitivity and good selectivity in enzyme inhibition detection.Compared with conventional biosensors,this platform can quickly obtain reliable results and reduce cost,which is expected to be an effective tool for screening enzyme inhibitors.2.A nanocomposite based on MOF-5[Zn₄O(BDC)₃;BDC=1,4-phthalic acid]and platinum nanoparticles(Pt NPs)was synthesized.The high specific surface area and good biocompatibility of MOF-5 and the electrocatalytic activity of Pt NPs was utilized to successfully construct the GA/GOx-HRP/MOF-5-Pt NPs/Pt electrode based on MOF-5-Pt NPs and dual enzymes(GOx and horseradish peroxidase(HRP)),and sensitive sensing of enzyme reaction substrates and inhibitors were realized.The sensor is easy to prepare,with high sensitivity,good stability and strong anti-interference ability observed.The excellent electrocatalytic performance superior to most biosensors based on GOx and HRP was obtained.The prepared enzyme-MOF composite modified biosensors exhibit a sensitivity as high as 126.0?A m M^-1 cm^-2to glucose in the linear range of 0.05?7.85 m M(R=0.9981),the LOD is 5.0?M.Since the activities of GOx and HRP are both inhibited by Hg²⁺,the dual-enzyme biosensor also shows excellent performance in the detection of Hg²⁺.Compared with the measurement result of the traditional ultraviolet method,the sensitivity of the obtained enzyme-modified electrode measurement to Hg²⁺is even better than that of the ultraviolet method.3.Transition metal sulfides are expected to exhibit excellent performance in the construction of biosensors due to their advantages such as easy synthesis,low cost,high conductivity,lots of active sites,and excellent catalytic performance similar to noble metals.Combining the high catalytic activity of CoS₂ and the good dispersibility of MWCNTs,we synthesized CoS₂-MWCNTs nanocomposites by one-pot hydrothermal method and successfully applied them to construct GOx modified electrodes.The experimental results show that the detection sensitivity is as high as 129.7?A m M^-1 cm^-2 to glucose in the linear range of 0.05?7.0m M(R=0.9960),the LOD is 1.0?M.And the prepared biosensor has good stability and repeatability.At the same time,based on the inhibition effect of Hg²⁺on GOx,the sensor can also be used for the detection of Hg²⁺.The nanocomposite has the advantages of simple preparation,low cost and stable properties.It has certain guiding significance for the construction and application of new enzyme modified electrodes and has important research value.