Nanomaterial-based Biosensors For Application In Environmental And Biological Monitoring

As one branch of the newly emerging field known as bioelectronics,biosensor is an interdisciplinary area involved with biology,chemistry,material,physics,nanotechnology,microelectronics,information technology,ect.Biosensors have valuable applications in chemistry,biology,environmental science,food industry,and medicine because of its excellent selectivity,high sensitivity,rapid response,low cost,continuous detection,easy to be miniaturized.Nanomaterials are attractive in the development of biosensors due to their novel optical,electrical,electrocatalytic and biocompatible properties.A large number of researches indicate that applying nanomaterials for the fabrication of biosensors will greatly improve the performance of the resulting biosensors.Based on the recent progress on the preparation and application of nanomaterials,this dissertation focuses on 1)preparation of nanomaterials-based biosensor for the detection of organophosphorous pesticides;2)preparation of immunochromatographic test strip(ITS)for biological monitoring of exposure biomarkers of organophosphorus agents.The dissertation consists of four chapters.In the first chapter,a critical review with regard to the biosensor and nanotechnology is given.Then the application of nanotechnology into biosensor was highlighted.Finally,a brief introduction of this dissertation research content and innovation were put forward.In the second chapter,an interface of biotin in chitosan hydrogel embedded AuNPs in situ was constructed by one-step electrochemical deposition.This deposited interface provided specific binding sites for avidin,which was further capable of attaching any biotinylated biomolecular.The immobilized AChE,showed excellent activity to its substrate and provide a quantitative measurement of organophosphate pesticide.AuNPs promoted electron transfer reactions and catalyzed the electro-oxidation of thiocholine,thus increasing detection sensitivity.Due to the inhibition of pesticides,this biosensor could be used for detection of dimethoate,and the linear range was 0.05 to 15 μg/mL.The detection limit was 0.001 μg/mL.In the third chapter,the sample pad of ITS was pretreated with the pretreatment buffer developed in our lab,and the stock solution of Au-TCP antibody was optimized,which realized direct detection of the analyte in the biological sample.A portable Au nanoparticles-based ITS was developed for rapid biomonitoring of 3,5,6-trichloro-2-pyridinol(TCP)in human saliva without any pretreatment,which holds a great promise for point-of-care and in-field diagnosis of exposure to pesticides.The sensor is capable of detecting a minimum of 0.47 ng/mL TCP standard analyte in 15 min with a linear range of 0.625-20 ng/mL.TCP was detected in saliva samples tested with the sensor and the commercially available ELISA kit.The quantified levels of TCP by the sensor were very consistent to those from a commercially available ELISA kit.In the fourth chapter,quantum dot was employed as a label to establish a zirconia nanopartilces(ZrO2)-based portable fluorescent ITS for simple,sensitive and selective biomonitoring of phosphorylated acetylcholinesterase(OP-AChE),an exposure biomarker of organophophorus agents.This is the first report on the development of test strip for the detection of OP-ACNE adduct,which provides a sensitive and low-cost sensing platform for on-site screening/evaluating organophosphorus pesticides and nerve agents poisoning.The sensor is capable of detecting a minimum of 4 pM OP-AChE standard analyte in 15 min with a linear range of 0.01-10 nM,which is comparable to that of mass-spectrometric analysis of organophosphorylated cholinesterase adducts.The recoveries were in the range of 95%to 108%in the detection of OP-AChE spiked in human plasma.In the fifth chapter,the first report on the development of Fe3O4@TiO2 magnetic nanoparticles-based disposable test-strip immunosensor combining with multi-enzyme labeled amplification strategy for sensitive and selective detection of phosphorylated acetylcholinesterase(OP-BChE)in human plasma.The use of Fe3O4@TiO2 not only overcome the difficulty in availability of commercial OP-specific antibody,but also avoids complex operation with easy separation of samples by magnetic forces.The sensor is capable of detecting a minimum of 0.01 nM OP-BChE standard analyte in 15 min with a linear range of 0.05-10 nM.The recoveries were in the range of 94-104%in the detection of OP-AChE spiked in human plasma.In the sixth chapter,the attempt to employ the novel nanomaterials grapheme in biosensor,take advantage of strong interaction between sodium phosphomolybdate(PMo12)and grapheme,PMo12-GS nanocomposite was synthesized and characterized.Then a PMo12-GS nanocomposites-based biosensor was developed for detection of ascorbic acid.This biosensor showed enhanced analytical performance with strong electrocatalytic activity,high sensitivity,stability and specificity for AA.