Preparation And Characterization Of Novel Carbon Nanocomposite Based Electrochemical Aptamer Sensor For Antibiotic Residues In Food

Antibiotics are widely used in the aquaculture industry,and the abuse of antibiotics directly leads to their residues in food,and accumulates in the human body through the food chain,triggering a variety of diseases.At present,there are many methods for detecting antibiotic residues in animal-derived foods,but the rapid detection on site is difficult.Electrochemical methods have become a hot spot in the field of rapid detection methods due to miniaturization.Although many electrochemical sensors have been reported in the field of food detection,there are still some shortcomings,such as poor specificity and easy signal interference.Aptamer technology has gradually been widely used in the field of electrochemical detection due to its good selectivity and editability.The specific recognition between the aptamer and the target molecule triggers the change of electrochemical signal,and the analysis and detection of the target molecule is realized by collecting the electrochemical signal.In this thesis,a series of aptamer electrochemical sensors for the detection of antibiotics have been constructed based new carbon nanocomposite materials,which provides new ideas and methods for the rapid detection of antibiotics in foods.The main research is as follows:(1)An electrochemical sensor based on UiO-66-NH₂/MCA/MWCNT@rGONR nanocomposite and aptamer was constructed to detect kanamycin(Kana).Zirconium metal organic framework(UiO-66-NH₂),melamine nanospheres(MCA)and multi-walled carbon nanotubes with core-shell structure were prepared by hydrothermal method and solution exfoliation method to reduce graphene oxide nanoribbons(MWCNT@rGONR).The UiO-66-NH₂/MCA/MWCNT@rGONR composite nanomaterial was obtained by ultrasonic mixing,which was used as an electrode surface modification material,combined with aptamer technology to construct an electrochemical sensor for the detection of kanamycin.UiO-66-NH₂/MCA/MWCNT@rGONR nanocomposite was characterized by scanning electron microscope(SEM)and transmission electron microscope(TEM),using X-ray diffractometer(XRD)and X-ray photoelectron spectroscopy(XPS).The instrument analyzed the composition of the composite material,and tested the construction process and electrochemical performance of the sensor by cyclic voltammetry(CV)and square wave voltammetry(SWV).The nanocomposite material improved the electron transfer efficiency and effective area of the electrode surface,increased the active site for fixing the aptamer,and realized the sensitive detection of Kana.After optimizing the experimental conditions,the linear detection concentration range of the sensor was 25?900 nmol/L and the theoretical detection limit was 13 nmol/L,and it had good selectivity,repeatability and stability.The results of standard addition and recovery experiments in actual samples and high performance liquid chromatography(HPLC)analysis results proved that the sensor had practical application potential in Kana detection.(2)An electrochemical sensor based on Ti₃C₂T_x/Au NPs nanocomposite and nucleic acid aptamer was constructed for the detection of kanamycin(Kana).Pencil graphite electrode after pretreatment(PPGE)pretreated by the chronoamperometry(it)was selected as the conductive substrate,and the composite material of titanium carbide(Ti₃C₂T_x)and gold nanoparticles(Au NPs)was prepared by the etching method and the in-situ synthesis method.The Ti₃C₂T_x/Au NPs composite material was functionalized with amino groups by(3-aminopropyl)triethoxysilane(APTES),and used as an electrode surface modification material,combined with aptamer technology to construct an electrochemical sensor for detection of Kana.SEM,XPS and XRD were used to characterize PPGE and Ti₃C₂T_x/Au NPs composite materials,and the construction process and electrochemical performance of the sensor were tested by electrochemical methods such as CV and SWV.The surface structure of PPGE after pretreatment was deformed,and the originally dense graphite structure becomed loose and stacked.Au NPs were evenly distributed on the surface of Ti₃C₂T_xand its layered structure through in-situ synthesis.These structures increased the effective active area and fitness of the electrode.The ligand was fixed at the site,which improved the sensitivity of the sensor.Under the best conditions,the theoretical detection limit of the sensor for Kana was 0.0071 nmol/L,the linear detection range was0.01?100 nmol/L and 100?1200 nmol/L,and it had good specificity,repeatability and stability.The actual sample addition and recovery experiment results and HPLC analysis results proved that the sensor had high detection accuracy and a good utilization potentiality in Kana detection.(3)An electrochemical sensor based on Ti₃C₂T_x/Mo S₂/MWCNT@rGONR nanocomposite and nucleic acid aptamer was constructed for simultaneous detection of kanamycin(Kana)and chloramphenicol(Cap).Ti₃C₂T_x,molybdenum disulfide quantum dots(Mo S₂),MWCNT@rGONR and titanium phosphate nanospheres were prepared by solution etching,stripping and hydrothermal methods,and Ti₃C₂T_x/Mo S₂/MWCNT@rGONR composite nanoparticles were obtained by ultrasonic mixing.Materials,the introduction of titanium phosphate nanospheres labeled with Cd²⁺and Zn²⁺as electrochemical beacon molecules,the construction of an aptamer electrochemical sensor realizes the simultaneous detection of Kana and Cap.The morphology and composition of the composite material and titanium phosphate nanospheres were characterized by SEM,TEM,EDS and XRD,and the construction process and electrochemical performance of the constructed sensor were studied by electrochemical methods such as CV and SWV.In the composite material,MWCNT@rGONR was wound and interspersed between the layered structure of Ti₃C₂T_x,and Mo S₂ quantum dots were evenly dispersed in between.These structures improved the electron transfer efficiency and effective area of the electrode surface and abundant active sites.Under the optimized experimental conditions,the theoretical detection limit of the sensor for Kana was 0.135 nmol/L,and the theoretical detection limit for Cap was 0.173 nmol/L.The linear detection ranges of the two antibiotics were0.5?2500 nmol/L,and it has good selectivity,stability and repeatability.This method has a high recovery rate in the standard addition recovery experiment of milk and fish meat.The HPLC test results proved that the sensor has good application potential in Kana and Cap detection.