Immunosensors ELISA

Starodub et al. [98] studied different constructions and biomedical applications of immunosensors based on fiberoptic and enhanced CL. They discussed three different approaches of immobilization of one of the immunocomponents on the fiberoptic surface. Good results could be achieved by the use of a special membrane closely connected to the fiberoptic, with sensitivities compared to that obtained by the ELISA method but with a faster rate of analysis. The sensor was... 

Abstract A significant number of immunochemical methods have been described for the determination of the most important emerging pollutants. The present chapter is a compilation of the information available today regarding immunochemical determination of industrial residues with a high potential risk of causing negative effects in the environment, wildlife, and public health. Homogeneous immunoassays, ELISAs, FIIAs, immunosensors, and selective immunoaffinity sample treatment methods have been reported for the analysis of an important number of these substances. The bases of these methods are briefly presented. 

Figure 3.32 — ISFT-ELISA immunosensor for HIV-serology. (Reproduced from [232] with permission of VCH Publishers).

Western blot and ELISA tests [63,64]. Besides the higher sensitivity, an improved selectivity has also been observed using the optical fiber immunosensor. Anti-E2 antibodies in all sera positive for anti-HCV (anti-core, NS3 and NS5) and HCV RNA (100% sensitivity) could be detected. Using Western blot tests, only 69% of anti-HCV (anti-core, NS3 and NS5) positive samples could be detected [63,64]. Furthermore, standard test for anti-HCV antibodies requires the use the three cited antigens (core, NS3 and NS5) because of its limited sensitivity. The high sensitivity of the optical fiber immunosensor, containing only the HVC E2 envelope protein, allows the identification of all RNA positive patients. 

With regard to immunosensors, a number of different reporter groups are used, including enzymes which convert a substrate into a highly coloured product (enzyme-linked immunosorbent assay, ELISA ) or which digest a substrate to give a photon of light to expose a film (chemiluminescence). 

Immunosensors have made a great contribution in the field of androgenic steroid detection, giving detection limits comparable to those obtained with standard ELISA procedures. Several electrochemical immunosensors have been developed for detecting testosterone, methyltestosterone,... 

The main practical environmental application of SPR has been as an immunosensor for the detection of phytosanitary products (Mullet, 2000). Recently, SPR immunodetection of 2,4D (Kim et al., 2007), DDT (Mauriz et al., 2006a, 2007), chlorpyrifos and carbaryl pesticides (Mauriz et al., 2006b) was found ten times more sensitive than ELISA methods, with detection limits in the ppt range, and an analysis time of less than 20 min. 

On the basis of an enzyme thermistor, Mattiasson et al. (1977) developed one of the first immunosensors. Immobilized antibodies against albumin are placed in a column and set into an ET. After injection of an albumin-sample and a known amount of enzyme-labeled albumin, both are separated from the sample matrix by antibody-antigen-interaction. After injection of a substrate, the change in heat is a measure of analyte concentration. The less heat produced means that more albumin has been bound. An elution step regenerates the ELISA. Due to its thermal detection principle, the procedure is called TELISA (thermometric enzyme-linked immunosorbent assay). Figure 3 shows the principle of the TELISA procedure in its sandwich configuration. 

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