Hudies On Immunosensors For Chlorpyrifos Pesticide Residues Detection

The electrochemical immunosensors are more likely to realize on-site rapid detectionby reason of the rapid response, high sensitivity and good selectivity. The efficientmodification of biomolecules on the electrode surface under the precondition ofmaintaining their activity and stability, and the enhancement of the signal response basedon the modification materials are the crucial factors of the fabrication of immunosensors.Besides, the sample preparation method is the key step in the analysis of pesticide residuesdetection.In this study, three kinds of amperometric immunosensors were developed based onsynergistic modification of different nanomaterials for chlorpyrifos pesticide residuesdetection and three different kinds of sample extraction methods were studied.1.1Studies on the immunosensor based on gold nanoparticles(GNPs) andchitosan-graphene sheets-methylene blue nanocomposite(CS-GS-MB)The CS-GS-MB had good electrochemical redox properties and good biocompatibility.The nanocomposite rich in a large amount of amino could modified on the electrodethrough the covalent binding with GNPs, and could combine the anti-chlorpyrifos antibodyby covalent crosslinking with the help of glutaraldehyde. Under optimal experimentalconditions, a good linear relationship between the relative current change and logarithm ofchlorpyrifos concentration in the range from1to500ng/mL and the detection limit of0.056ng/mL were obtained. The immunosensor had good reproducibility and stability,nevertheless the regeneration was not satisfactory enough.1.2Studies on the immunosensor based on multiwall carbonnanotubes/polyaniline/chitosan (MWCNTs-PANI-CS) and Au nanoparticles(AuNPs)The MWCNTs-PANI was synthesized by in situ polymerization method and thendispersed in CS. The nanocomposite had good electrochemical activity, high conductivityand strong chemical stability. AuNPs provided a good interface for antibodyimmobilization and maintained the activity of antibody to sustain the effective specificbinding with pesticide. Under optimal conditions, the relative current changes wereproportional to chlorpyrifos concentrations in the ranges of0.1-40ng/mL and40-500ng/mLand the detection limit was0.060ng/mL. The immunosensor had good reproducibility andregeneration, the stability had yet to be improved. 1.3Studies on the immunosensor based on NiAl-layered double hydroxide/graphenenanocomposites (NiAl-LDH-GS) and hollow gold nanospheres (HGNs)Under the low-temperature condition, the graphene oxide served as the supportingtemplate of the growth of NiAl-LDH and subsequently was processed by reduction toobtain the NiAl-LDH-GS nanocomposite. The composite showed good electrochemicalperformance. The proposed immunosensor presented wide linear range (5-150and150-2000ng/mL), low detection limit (0.052ng/mL) and good performance.Comparing the performance of above three kinds of immunosensors, the resultsshowed that the immunosensor based on NiAl-LDH-GS and HGNs presented lowerdetection limt, wider detection range and more outstanding reproducibility, stability andregeneration.2. Three different sample preparation methods involving the oscillation extractionmethod, the ultrasonication and centrifugation extraction method and the ultrasonicationand filtration extraction method were studied. By comparison of the recoveries andprecision, the ultrasonication and centrifugation extraction method was the mostappropriate and efficient for the immunosensor.