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Fabrication Of The Enzymatic Immunosensor For Shigella Flexneri Detection Based On Multi-Wall Carbon Nanotubes And 4-SPCE

Posted on:2011-09-13Degree:MasterType:Thesis
Country:ChinaCandidate:X J ZhanFull Text:PDF
GTID:2178360305468942Subject:Food Science
Abstract/Summary:PDF Full Text Request
Shigella spp is one of the major causes of human infectious diseases and is responsible for millions of cases of diarrhea worldwide every year. More than one million deaths occur yearly due to infections with Shigella spp. and the victims are mostly children of the developing world. So as to deal with the global threat of disease and death caused by Shigella, its detection is very important for public health.In the past decades, electrochemical immunosensors based on the specificity of antigen-antibody interactions with electrochemical transduction, have become an attractive subject for food analysis, clinical diagnosis, environmental monitoring and other fields.The rapid development of new nanomaterials and nanotechnologies has provided many new opportunities for electroanalysis. Particularly, multi-wall carbon nanotubes (MWCNT) exhibit promising potential within the realm of bioelectrochemistry as the matrix to incorporate biorecognition elements and construct biosensors.The comments of this paper was described as follows:1 Preparation of Shigella flexneriIn this experiment, Shigella flexneri (S. flexneri) was successfully prepared. The concentration of S. flexneri (1011 cfu/mL) was acquired by plate colony-counting method. Then inactivated with formaldehyde at a concentration of 0.4%(v/v) for 12 h at room temperature. Experimental results showed that S. flexneri possessed good bioactivity. Following experiment could be successfully carried on because of the supportment of the above work.2 MWCNT modified four-channel screen-printed carbon electrode for hydrogen peroxide determinationA MWCNT modified four-channel screen-printed carbon electrode was successfully constructed to be used to detect hydrogen peroxide. Cyclic voltammetry (CV) was used to measure the concentration of hydrogen peroxide. The results showed that the MWCNT could enlarge the effective surface area of four-channel screen-printed carbon electrode and could enormously enhance the electron transfer. The sensitivity and correlation coefficient for hydrogen peroxide detection were 0.3192μA/(mmol/L) and 0.9979. The procedure is simple and the results obtained are satisfied. 3 Fabrication of enzymatic immunosensor for Shigella flexneri detection based on MWCNT/DMF composite and four-channel screen-printed carbon electrodeAn immunosensor based on MWCNT/DMF composite was successfully constructed. The horseradish peroxidase labeled antibodies to S. flexneri (HRP-anti-S. flexneri) was co-immobilized on the four-channel screen-printed carbon electrode surface by crosslinking with glutaraldehyde to form a combined sensing and electron transfer system. CV was carried out to characterize the electrochemical properties of different electrodes and to detect S. flexneri. When the antigen (S. flexneri) was bound to the antibody on the surface of the sensing film, a "barrier" occurred between the electrode and the redox centres in the bound HRP. Under optimal conditions, concentrations of S. flexneri from 104 to 109 cfu/mL could be detected, with a detection limit of 3.4×103 cfu/mL (S/N=3).The immunosensor showed satisfactory selectivity, reproducibility, stability and accuracy.4 Rapid detection of Shigella flexneri with MWCNT/chitosan modified four-channel screen-printed carbon electrodeA disposable S. flexneri immunosensor based on MWCNT/chitosan/ HRP-anti-S. flexneri biocomposite on four-channel screen-printed carbon electrode without any other cross-linked reagents has been developed. The MWCNT/chitosan matrix provided a congenial microenvironment for the immobilization of HRP-anti-S. flexneri and promoted the electron transfer. Due to the strong electrocatalytic properties of HRP and MWCNT toward H2O2, the current signal was significantly amplified. The atomic force microscope (AFM) technology was used to characterize the surface morphologies of different electrodes. And CV was carried out to characterize the electrochemical properties of different electrodes and detect S. flexneri. Under optimal conditions, concentrations of S. flexneri from 104 to 109 cfu/mL could be detected, with a detection limit of 2.3×104 cfu/mL (S/N=3). The proposed immunosensor displayed a satisfactory stability, reproducibility and accuracy. Moreover, the immunosensor was inexpensive, relatively simple to fabricate and had a potential possibility for early assessment of S. flexneri.5 A disposable immunosensor for Shigella flexneri based on MWCNT/sodium alginate composite and four-channel screen-printed carbon electrodeA novel S. flexneri immunosensor based on HRP-anti-S. flexneri immobilized by physical adsorption on the MWCNT/sodium alginate (MWCNT/SA) composite modified four-channel screen-printed carbon electrode surface was successfully fabricated. In this strategy, MWCNT/SA biocomposite acted as the matrix to adsorb and immobilize HRP-anti-S. flexneri. The preparation process of modified electrodes was characterized with AFM and CV. The analytical performance of proposed immunosensor toward S. flexneri was investigated by CV. Under optimal conditions, the concentration of S. flexneri from 104 to 1010 cfu mL-1 could be detected, with a detection limit of 3.1×103 cfu/mL (S/N=3). The specificity, reproducibility, stability and accuracy of the proposed immunosensor were also evaluated. The proposed immunosensor showed simply fabricative, economical, efficient and potential application for early assessment of S. flexneri.
Keywords/Search Tags:Enzymatic immunosensor, Multi-wall carbon nanotubes, Four-channel screen-printed carbon electrode, Atomic force microscope, Cyclic voltammetry
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