Study On The Sensing Interfaces Fabrication Of Electrochemical Impedance Immunosensor And The Application For The Detection Of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants (POPs) widely present in the environment, many which are carcinogenic, teratogenesis and mutagenicity. 1-Pyrenebutyric acid (PBA) is one of PAHs derivatives and harmful for human being and other flora and fauna. Therefore, it is of necessary to develop a sensitive, rapid and cost-effective method for PAHs detection. As an efficient trace analysis method, electrochemical immunosensor possesses the merits of high sensitivity, quick analysis, strong selectivity and simple structure, etc. However, few researches have been concentrated on utilizing electrochemical impedance immunosensor to monitor PAHs and its derivatives up to now. Further investigations should be carried out for the electrochemical immunoassay for small molecules of PAHs.1-Pyrenebutyric acid (PBA) was chosen as the examination object in this paper. Different immobilized technologies were adopted to fix the PAHs antibody on the electrode surface effectively, and then sensitive and specific sensing interfaces were constructed. The modified sensor interface is taken as the sensitive element. Then the construction process of the immunosensor is described by electrochemical means such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), etc. The quantitative analysis for PBA was realized according to the variation of the electron transfer impedance (Ret) after the immunoreaction between antigen and antibody on the sensing interface detected by EIS.Glassy carbon is selected as the basal electrode. The anti-PAHs antibody was steadily immobilized at the nano-Au/GC electrode due to large specific surface area and satisfactory biocompatibility of gold nanoparticles. The electrochemical behavior of the modified electrode in the electrolyte is monitored according to EIS and CV. It is shown that the quantity of immunocomplex combined to the nanometer gold modified electrode surface would rise with the increase in the concentration of the PAHs sample. Therefore, the electronic transfer resistance on the electrode surface increases by the redox, which resulted in the increase in the electron transfer impedance on the electrode surface. It is proved that the impedance spectroscopy could be adopted in the qualitative detection and analysis for PBA. In addition, the EIS immunosensor for the detection of PAHs is set up preliminary during the experiment.A simple, highly sensitive, and label-free electrochemical impedance spectroscopy (EIS) immunosensor was developed using Nafion and gold nanoparticles (nano-Au/Nafion) composites for the determination of PBA. Under the optimal conditions, the amount of immobilization of antibody was significantly improved on the nano-Au/Nafion electrode due to the synergistic effect and biocompatibility of Nafion film and gold nanoparticles composites. The results showed that the sensitivity and stability of nano-Au/Nafion composite electrode for PBA detection were much better than those of nano-Au modified glassy carbon electrode (nano-Au/GCE). The plot of increased electron transfer resistances (Rets) against the logarithm of PBA concentration is linear over the range from 0.1 to 150 ng-mL"1 with a detection limit of 0.03 ng·mL-1. The selectivity and accuracy of the proposed EIS immunosensor were evaluated with satisfactory results.An electrochemical impedance spectroscopy (EIS) immunosensor for the detection of PAHs was developed by immobilizing antibody through the Au-S covalent bond. A pretreated gold electrode is first immersed in mercaptoacetic acid solution to form a self-assembled monolayer (SAM). Then anti-PAHs antibodies are immobilized to the SAM by means of covalenting with a stable acyl amino ester intermediate generated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydrosuccinimide(NHS). In the presence of Fe(CN)63-/Fe(CN)64- as a redox probe, the electrotransfer resistances (Rets) were directly detected by EIS after the immunosensor specific binding with PBA of different concentrations. A linear relationship between the increased Ret and the logarithmic value of PBA concentrations was found in the range of 0.05-50 ng·mL-1 with the detection limit of 0.05 ng·mL-1. The regeneration and repeating characteristics were also studied to be good.