Regulation Method And Research Of Biosensor Interface Probe Performance And Its Application In Pesticide Detection

In this paper,a variety of tetrahedron DNA Tetrahedral DNA（nanostructures）with different sizes were designed and characterized by polyacrylamide gel electrophoresis.Bying its unique and rigid tetrahedral structure,the biological probe on the sensing interface can always maintain the orientation perpendicular to the sensing interface,which is of great significance to improve the order of DNA recognition probes on the biosensor interface.By studying the electrochemical properties of TDN electrodes with different sizes,a series of comparative experiments were carried out with the performance of conventional aptamer sensors with single stranded DNA modified sensing interface.Not only the influence factors of TDN on the sensing interface were obtained,but also a variety of sensors were prepared using TDN to detect a variety of pesticide residues.The experimental results showed that the addition of TDN can improve the sensitivity and accuracy of aptamer biosensor.In order to study the method to improve the sensitivity of the sensor,we not only studied the regulation of the order of the sensing interface by TDN,but also adopted the way of porous electrode to regulate the sensing interface.The sensing interface modified by porous electrode material has a unique spatial structure.It not only improves the transmission rate of pesticide molecules in the detection bottom solution and the mass transfer rate of electrochemical process,but also provides extremely rich electrochemical active sites,which greatly improves the analytical performance of aptamer sensor.Based on the above two methods of regulating the biosensor interface,the sensitivity,reproducibility and stability of aptamer electrochemical biosensor have been significantly improved.The main contents include:1.By designing and synthesizing three groups of TDN with different sizes,the parameters of TDN sensor are compared with those of conventional aptamer sensor which using single stranded DNA as recognition probe.Comparing by using control variable method,which is used to analyze and explore the influencing factors of TDN on the sensing interface.We study the relationship between the size of TDN and the probe spacing on the sensing interface.Then the relationship between the probe spacing and the micro properties of the sensing interface,such as probe activity,hybridization quantity,assembly density,hybridization efficiency,analytical performance and surface hybridization kinetics,was discussed.The influence factors of TDN on aptamer electrochemical sensor were summarized.2.The electrochemiluminescence（ECL）biosensor interface was regulated efficiently and orderly based on TDN.Using the advantages that Fe-MOF（NH₂-MIL-88）can promote the ECL performance of Cd Te quantum dots in K₂S₂O₈ system,a new ECL sensor for the detection of acetamiprid was constructed.The ECL signals of TDN sensor and conventional single strand aptamer（c-DNA）sensor are compared.And the linear range of TDN sensor is 0.10pmol/L～0.10μmol/L,the detection limit is 0.034 pmol/L;The linear range of c-DNA sensor is1.0 pmol/L～0.010μmol/L,the detection limit is 0.18 pmol/L.Obviously,the addition of TDN can improve the analytical performance of the sensor for the detection of pesticide residues.The TDN sensor constructed in this chapter is applied to the detection of water samples,and the effect is excellent.3.Based on hollow Cu/Co-MOF as the carrier of beacon and the catalyst of ECL luminescence performance of catalytic system,and the new ECL sensor was constructed to detect malathion by cooperating with TDN to regulate the order of sensing interface.The synthesized hollow Cu/Co-MOF not only has very rich active sites,but also has very low density,which greatly reduces the mass transfer resistance of malathion in the detection bottom solution.While improving the conductivity of the electrode,it can also effectively catalyze luminol-K₂S₂O₈ system and greatly improve the luminescence performance of ECL.The linear range of the TDN sensor is 0.10 pmol/L～0.10μmol/L,the detection limit is 0.059 pmol/L;The linear range of c-DNA sensor is 1.0 pmol/L～0.010μmol/L,and the detection limit is 0.74pmol/L.Appling the sensor to the actual sample detection,which performanced excellent results.4.Based on the mixed valence Ce-MOF can catalyze the electrochemical response signal of Thionine（Thi）,a new electrochemical aptamer sensor using TDN to regulate the sensing interface was constructed to detect chlorpyrifos.The mixed valence Ce-MOF can catalyze and amplify the electrochemical signal generated by Thi through the mutual conversion between Ce（III）and Ce（IV）contained in itself,so as to improve the sensitivity of the sensor.At the same time,the surface of Ce（III,IV）-MOF has very rich catalytic active sites,which improves the load of Thi on the sensing interface.Combined with the regulation of TDN on the order of the sensing interface,the analysis performance of the sensor is further improved.The linear range of chlorpyrifos by TDN sensor is 10 fmol/L～0.10μmol/L,the detection limit is 3.6 fmol/L;The linear range of c-DNA sensor is 1.0 pmol/L～0.010μmol/L,and the detection limit is 0.095pmol/L.Through the application experiments in the above three chapters,it is repeatedly verified that the introduction of TDN is of great significance to improve the sensitivity,stability and reproducibility of the aptamer sensor.5.A three-dimensional porous electrode（3D-GO/CS/GCE）was prepared by in-situ electrodeposition.The amount of DNA on the sensing interface was further amplified by collaborative cascade self-assembly technology.Based on the principle that DNA can react with molybdate to produce electrical signal,a new label free electrochemical aptamer sensor was constructed to detect acetamiprid residue.Linear range:0.10 pmol/L～0.10μmol/L,detection limit:0.071 pmol/L.The method has been applied to the determination of acetamiprid residues in tea,which provides a new idea for the highly sensitive detection of pesticide residues in agricultural products in the future.