Study Of The Electrochemical Impedance Immunosensor

Electrochemical impedance immunosensor has been demonstrated to be an effective method for probing the targets of antigens /antibodies in the samples by monitoring the interfacial properties of the modified electrode. Electrochemical impedance immunosensing technique, which incorporates high sensitivity of impedancic response and high specificity of antibody-antigen immunoreaction, is sensitive to signal of electronic transfer impendace of the biomolacular on the electrode interface. It presents some outstanding advantages including desirable simplicity, high sensitivity, rapid response, wide detection range, real-time digital output, and free from tracer labeling and sample purification etc. This technique may breakthrough some bottlenecks of the traditional analytical methodologies, showing an attractive future of potential applications in the biochemical diagnosis of clinical diseases. In this paper, on one hand, based on the biotin-avidin amplified system, a new electrochemical impedance immunosensing technique with high sensitivity has been developed. On the other hand, the electrochemical impedance immunosensors are fabricated by new material bio-molecular modification techniques for the diagnosis of human IgG and some clinical diseases such as anti-Sj?gren's syndrome B(SSB). The detailed matericals are shown as follows:(1) p-aminobenzenthiol (p-ABT) was self-assembled on the surface of the gold electrode, then was electrochemical polymerizational deposited resulting in a stable, dense and ordered p-ABT nanocomposite film on the interface of the electrode. After the immobility of functionalized carbon nanotubes (CNTs), biotinted-goat antihuman IgG was modified on the electrode surface by introducing the biotin-avidin system (BAS) to detect human IgG. An electrochemical impedance immunosensor with favorably high sensitivity was founded. The linear range of the resulted immunosensor was observed from 0.01 to 100 ng/mL with a detection limit of 0.0075 ng/mL.(2)An impedance immunosensor has been proposed initially for the determination of anti-SSB antibodies using hydroxyapatite (HA) and CNTs on glass carbon electrode. HA and CNTs were self-assembled on a glass carbon electrode to form HA/CNTs composite film for immobilizing SSB antigens. It was found that the synthesis of the biocompatible HA and electron-transferring CNTs could facilitate the immunosensor good electrochemical detection performances, especially by way of the impedance spectra. It could detect anit-SSB antibodies in the linear response range of 1:800 to 1:50 dilution ratios, with a detection limit of 1:853 dilution ratio. The practical feasibility of the developed immunosensor for detection of anit-SSB antibodies was further verified by recovery tests using the serum-diluted antibody samples. Such an immunosensing method should be promisingly tailored as a new alternative method for the determination of auto-antibodies in the clinical diagnosis of autoimmune diseases.(3) A hybrid material formed by electrochemical polymerizational depositing HA and collagen was employed as the interface design of electrochemical impedance immunosensor, on which the antibodies were bound. The detection performances of the resulting immunosensor were investigated by use of the antibody-antigen model system of goat antihuman IgG and human IgG. It was found that the developed sensing interface have some advantages such as the activation-free of the sensing interface and the relatively high immunological activities of antibodies. The proposed immunosensor could detect human IgG in the linear range of 20 to 500 ng /mL with a detection limit of 16 ng/mL. Such an interface design with the hybrid nano-sized materials should be tailored as a new valuable alternative extensively used in clinical immunoassays.