Prepararion And Application Of The Electrochemical Immunosensor Based On Chitosan Nanohybrids Modified Electrode

1. A novel strategy for the fabrication of sensitive immunosensor to detectα-fetoprotein (AFP) in human serum has been proposed. GNP/CNT hybrids were produced by one-step synthesis based on the direct redox reaction. The proposed immunosensor by using GNP/CNT/Ch hybrid film as the immobilization matrix of AFP offers an excellent amperometric response of ALP–anti-AFP to 1-NP. The accuracy of the AFP determination was examined by comparing the results obtained with this electrochemical immunoassay (EIA) with those obtained with classical IRMA. The results show that the two methods were in acceptable agreement. Under the optimized experimental conditions, the resulting immunosensor could detect AFP in a linear range from 1 to 55 ng ml-1 with a detection limit of 0.6 ng ml-1. This method could be further developed for practical clinical detection of serum AFP level and other tumor markers. The biosensor possesses good bioactivity, comparable detection limit and linear range, and acceptable storage stability.2. The hybrid film of gold nanoparticles/ionic liquid-chitosan (GNP/IL-Ch) was firstly prepared by a simple one-step synthesis and used as an efficient immobilization matrix to fabricate an immunosensor. The GNP/IL-Ch film not only prevents the leakage of the IL units, but also produces a well-defined voltammetric signal due to the synergistic effects of the IL units and GNPs. By immobilizing an alkaline phosphatase (ALP)-labeled antibody in GNP/IL-Ch film, a sensitive amperometric immunosensor has been developed for prostate specific antigen (PSA). Under the optimized conditions, the immunosensor exhibits a linear range from 1.0 to 80 ng ml-1 of PSA.3. In this work, a new strategy was presented to construct an immunoassay channeling sensor by incorporating bio-recognition elements in the mesopores of SBA-15. The approach was based on a LBL assembly technique and one-step immunoassay for AFP detection. A novel immunoassay channeling sensor forα-fetoprotein (AFP) was proposed by incorporating biorecognition molecules into the mesopores of well-ordered hexagonal SBA-15. The encapsulated ALP-labeled antibody retained its catalytic and immunological bioactivities in SBA-15 mesopores. The DPV peak currents decreased with the increased AFP concentration due to increasing spatial blocking and impedance from the formed immunoconjugates. Under the optimized conditions, the constructed immunosensor could detect AFP in a linear range from 1.0 to 150 ng ml-1with a detection limit of 0.8 ng ml-1.In addition, interference experiments suggested that the immunoassay channels displayed good bio-specificity and bio-selectivity.4. One-step synthesis of silver nanoparticles/carbon nanotubes/chitosan film (Ag/CNT/Ch) was firstly proposed as a novel immobilization matrix for the enzymes to fabricate sensitive glucose biosensor. The biosensor was prepared by embedding horseradish peroxidase (HRP) and glucose oxidase (GOD) in Ag/CNT/Ch hybrid films based on layer by layer technique. The electron mediator, o-phenylenediamine (OPD), was also co-immobilized with HRP in the inner layer on the surface of an indium tin oxide (ITO) electrode. Hydrogen peroxide produced by the GOD catalytic oxidation of glucose was then detected by OPD in the presence of HRP. Under the optimized experimental conditions, the resulting biosensor could detect glucose in a linear range from 0.5 to 50μM with a detection limit of 0.1μM at a signal-to-noise ratio of 3. The sensitivity was calculated as 135.9μAmM-1. The proposed biosensor offered sensitive amperometric responses to glucose based on the Ag/CNT/Ch films.