Study On Electrochemical Biosensor Based On Functioned Nanomaterial For CEA And Hg²⁺ Detection

Canser has been the disease resulting in most death of human,however early diagnosis and cure could improve effectively survival rates of patients.Environmental pollution was one of most important factors inducing canser,therefore,developing the biosensor platform for detecting clinical tumor markers and environmental heavy metal ions has been focused by numerous researchers.In this thesis,a series of electrochemical sensors were developed based on functioned nanomaterials,including polymer monodisperse nanospheres,noble metal nanoparticles,magnetic composite nanomaterials and so on,which could improve the sensitivity and decrease the detection limit of the electrochemical biosensor.Among,carcinoembryonic antigen and heavy metal Hg²⁺were effectively detected by those electrochemical biosensors.The application of nanomaterials could provide the possibility for making portable and affordable devices for online detection to meet the requirement of modern medical diagnostics and environmental research.There are six chapters in this thesis,and main contents are listed as follows:1.Ferrocenyl nanospheres were synthesized by coordination polymerization and characterized by transmission electron microscopy,energy dispersive X-ray spectrometry,and infrared spectroscopy.A new electrochemical immunoassay based on a sandwich format was developed for carcino embryonie antige using ferrocenyl polymer nanospheres as the recognition elements.Under the optimal conditions,the electrochemical signal increased with the concentration of the analyte from 0.01 to 50 ng mL^-1 with a limit of detection equal to 0.004 ng mL^-1.The immunosensor had realized the high sensitivity detection of CEA.2.A novel chitosan modified AgI was synthesized and was characterized by transmission electron microscope and fourier transforminfrared spectroscopy.The synthesized nanoparticles were spherical in shape,with the particles size being 100 nm,the particles were employed to construct immunosensor as signal markers.The immunosensor had an excellent electrochemical performance in detection of CEA.And its impedance response increased with the increase of the logarithm of CEA concentration,exhibiting a good linear relationship in the range of 0.1 ng mL^-1 to 80 ng mL^-1,with the detection limit of 0.05 ng mL^-1.This immunosensor had good specificity and stability.3.Au@Ag core-shell nanoparticles were synthesized by simple reduction of Ag⁺around Au nanoparticles and functionalized by DNAzyme.Based on thymine-Hg²⁺-thymine binding mode,a sensitive aptamer biosensor was constructed by utilizing functionalized Au@Ag core-shell nanoparticles as labels,and the sensitivity was enhanced by DNAzyme due to the catalysis toward H₂O₂.Under optimal conditions,square wave voltammetry was carried out to measure the current derived from Au@Ag nanoparticles labels.The current response of biosensor increased with the increasing of Hg²⁺concentration,which presented linear relation in the range of 0.002-20?g L^-1with limit of detection of 0.006?g L^-1.This biosensor could be appliyed in the detection of real water samples.4.A novel magnetic nanocomposite?Fe₃O₄@SiO₂@CeO₂?was fabricated by loading cerium oxide onto the surface of Fe₃O₄@SiO₂ magnetic nanoparticles to solve the difficult problem about solid-liquid separation.Then the nanocomposite was modified by DNA and electron mediators,which were utilized as lables to construst the electrochemical biosensor to detection of Hg²⁺.The sensitivity was enhanced due to the catalytic activity of the magnetic nanocomposite.Under the optimal conditions,the electrochemical signal increased with the concentration of the analyte from 0.05 to 100 nM with a limit of detection equal to 0.001 nM.This DNA biosensor had good specificity,stability and reproducibility.