Research On Several Nanocomposite-based Electrochemical Biosensors

Electrochemical biosensors take specific biometric components?enzymes,nucleic acids or antibodies/antigens,etc.?as its molecular recognition component to sense specific chemical substances in samples and convert the chemical informations of the analyte into electrical signals.According to the different detection signals,electrochemical biosensors can be divided into potentiometric biosensors,amperometric biosensors,capacitive biosensors and conductive biosensors,which have broad applications in clinical,environmental and food fields.In recent years,biosensors based on enzyme and aptamer have been extensively studied,and the development of various novel composite materials to realize the high-efficient immobilization of enzyme/nucleic acid molecules has become one of the research frontiers in this field.In this dissertation,we reviewed the principles,the fabrication methods,and applications of electrochemical biosensors.A series of innovative work has been carried out based on the development of new composite materials to construct new high-efficiency biosensors and apply them to the detection of phenolic compounds and organophosphorus pesticides.The main contents are as follows:?1?Thepreparationofchitosan?CS?/polycaffeicacid?PCA?-tyrosinase?Tyr?-multiwallcarbonnanotubes?MWCNTs?composites?CS/PCA-Tyr-MWCNTs?was conducted.The applications of prepared biosensors in the sensing of Tyr substrates?phenol and catechol?and the detecting of catechol in water samples were carried out.Caffeic acid?CA?,Tyr and MWCNTs were mixed together in proportion.With CA as the monomer and Tyr as catalyst for the catalytic oxidation polymerization of CA,Tyr were immobilized in PCA.At the same time,MWCNTs were doped in the poly caffeic acid-Tyr?PCA-Tyr?composite and the conductivity of the composite was thus improved.The biosensor was constructed by dropping PCA-Tyr-MWCNTs nanocomposite on glassy carbon electrode to study the electrochemical behavior of catechol on the modified electrode.In addition,the recovery of phenolic compounds in water samples was determined.?2?ZIF-8 is a kind of porous nanomaterial.Zeolite imidazole/graphene oxide composites?ZIF-8/GO?were synthesized by adding graphene oxide into 2-methylimidazole and zinc nitrate hexahydrate mixed methanol solution.Utilizing the large pores and large specific surface area of ZIF-8/GO,Tyr was entrapped in the prepared nanocomposites,and the obtained biocomposite material was dripped on the surface of the electrode to construct an excellent Nafion-ZIF-8/GO-Tyr/GCE sensor,and the prepared sensor was applied to the sensitive detection of phenolic compounds and organophosphorus pesticides.?3?The aptamer-modified electrode?CS@Apt@UiO-66/Au?was constructed by immobilizing UiO-66 and malathion aptamer on Au electrode with the help of chitosan.Theelectrode fabrication parameters were optimized,and the resultant aptasensor had sensitive response to malathion with a low limit of detection(0.0026mg L^-1),and a wide linear range(0.01²00?g L^-1)under optimized conditions.The aptasensor performed very well in detecting malathion-spiked real food matrices such as apple and cucumber,with good recoveries?89.9%¹03.4%for apple,82.7%¹15.7%for cucumber?and small RSD values ranging between 1.15% and 4.32% obtained.