Study On Three Electrochemical Immunosensors Based On Multifunctional Nanoprobes

Electrochemical immunosensor is a device that can transform easily the antigen-antibody interaction into measurable electrochemical signal.It is one of the most popular research areas in electroanalytical chemistry,owing to the specificity of immunoreaction and the simplicity and sensitivity of electroanalytical chemistry detection.The exciting advancement of nanomaterials not only could provide an excellent matrix for immobilizing antibody/antigen but also supply novel signal amplification stratigies for the development of high-sensitive electrochemical immunosensor.In this thesis,three new electrochemical immunosensors for the detection of human immunoglobulin(IgG)and carcinoembryonic antigen(CEA)were fabricated based on multifunctional nanoprobes and good analytical performance was acquired,respectively.Details were described as follows:(1)An electrochemical immunosensor based on silver nanoclusters and gold nanoclusters was fabricated.The immunosensor prepared by using silver nanoclusters for the immobilization of the capture antibodies and using gold nanoclusters for the labelling of detection antibodies.Then,electrochemical-promoted silver deposition on gold nanoclusters was performed and the signal of silver electrochemical oxidation was used to detect CEA quantitatively.Under the optimal conditions,the immunosensor exhibited the broad linear concentration range of 0.01 pg·mL-1 to 100 ng·mL-1 and a low detection limit of 1 fg·mL-1.Compared with other immunosensors based on gold and silver nanoparticles,the immunosensor increased the interaction efficiency of antibodies by using ultrasmall nanoclusters.Besides,the sensitivity of the immunosensor was improved by utilizing the dual signal enhancement of in-situ reduction and electrochemical-promoted reduction.(2)A label-free electrochemical immunosensor was constructed based on the strategy of functional silver nanoprobe and Fe3O4 magnetic nanoparticles.The immunosensor was constructed through immobilizing Fe3O4 magnetic nanoparticles crosslinked with antibody on the electrode surface on which silver nanoparticles had been pre-deposited.The silver nanoparticles not only enhanced conductivity,but also provided the detected signal.The good conductivity of Fe3O4 magnetic nanoparticles accelerated the electron transfer rate.And antibodies were fixed on the electrode surface firmly through the strong magnetic force between Fe3O4 magnetic nanoparticles and magnetic electrode.After the parameters optimization,the immunosensor displayed excellent analytical performance with IgG as a model analyte.A broad linear relationship between the peak current on LSV and the logarithmic values of IgG concentrations from 0.1 pg·mL-1 to 1.0 ?g·mL-1 and a low detection limit of 0.05 pg·mL-1 were obtained.The immunosensor avoided the application of secondary antibodies.The stability of the immunosensor was ascribed to the application of the surface-confining electrodeposition,magnetic interaction and chemical crossing-linking.(3)The charge-labeled electrochemical immunosensor based on gold nanorods was fabricated.Gold nanorods self-assembled with thiolated reagents were applied to produce negative charge and immobilize antibodies.Using carbon nanotubes-chitosan composite as the platform and through sandwich-type immunoreaction,gold nnaorods were introduced onto the sensor surface.And the interface electrostatic interaction was studied via the electrochemical signal of redox probe Fe(CN)63-.The big surface area of glod nanorods enhanced the immbolization of negatively-charged molecules and antibodies.And the sensitivity of this immunosensor was improved by utilizing repulsive interaction between gold nanorods self-assembled negative charge layer.After the parameters optimization,the broad linear concentration range of 1 fg·mL-1 to 100 ng·mL-1 and a low detection limit of 0.1 fg·mL-1 were obtained.This work aimed to investigate the feasibility of charge-labelled high-sensitive immunosensor.Compared with some other immunosensors using Fe(CN)63-as the redox probe,this immunosensor had much lower detection limit.