Haptene sensors

Fig. 13a-e. The increase of the signal intensities by the addition of the dendritic complexes composed of IgGs and protein A. The hapten was immobilized to the surface of the SPR sensor chip. The increase of the signal intensities on the complex formation of hapten with the antibodies were monitored. The addition of mouse IgG specific for hapten (Abl) (a), the complex of the Abl with protein A (b), one to one complex of Abl with anti-mouse IgG (Fc) antibody (Ab2) (c), two to one complex of Abl with Ab2 (d), and two to one complex of Abl with Ab2 in the presence of protein A (e)... 

A sensor array where different haptens are immobilized at well-defined areas on a plain glass surface has been developed [66], Using an automated flow injection system it was possible to incubate all areas on the chip with analytes, specific antibodies, secondary HRP-labeled antibodies, and CL substrate. Measurement of the light output via imaging performed with a CCD device allowed determination of the analytes present in the sample on the basis of the spatial localization of the CL signal. 

HAp coatings, 14 105 HapMap project, 20 839 Hapten-antibody interactions, 9 64 Haptic sensor, for skin conditions, 3 749 Harcros antifoam, commercial defoamer, 3 24 It... 

For the determination of these compounds a binding inhibition immunoassay, consisting of the competitive immunoreaction of the unbound antibody present in an analyte-antibody mixture with the hapten derivative immobilized at the sensor surface, has been applied. With the aim of assuring the regeneration and reusability of the surface without denaturation of the immobilized molecule, the formation of an alkanethiol monolayer was carried out to provide covalent attachment of the ligand to the functionalized carbodiimide surface in a highly controlled way. For DDT, the assay sensitivity was evaluated in the 0.004 - 3545 pg/l range of pesticide concentration by the determination of the limit of detection 0.3 pg/1 and the I50 value 4.2 pg/1. 

The non-competitive FI immunoassay for haptens recently reported by Gunaratna and Wilson [219] offers rather an interesting means for developing flow-through sensors for this type of compound. 

Antibodies against small molecules (haptens) can be readily prepared. It has been suggested that Ab against, for example, pesticide gas molecules can be immobilized on mass sensors and used for sensing of such gaseous compounds. 

The utihzation of fluorescence dyes for analytical measurements enhances the sensitivity for the detection of the molecules of interest. First, Cronick and Little made use of evanescent wave excitation for a fluorescence immunoassay, in 1975. By using totally internally reflected light, they excited the fluorescence of a fluorescein-labeled antibody which has become bound to a hapten-protein conjugate adsorbed on a quartz-plate in an antibody solution [41]. Contrary to the label-free high-refractive-index sensors where the mass of the molecule of interest is... 

Antigen, hapten Antibody Conformation change, weight change Electrode, FET (indirect also by indicator reaction), piezoelectric sensor... 

Nevertheless, a steady rapid development of immunotests can be observed, especially in the field of environmental monitoring [l]-[3], where the question of costs has become so important that the establishment of an immunotest can be worthwhile in spite of all the facts mentioned above. In the development of chemical sensors, efforts are also being made to utilize the biochemical recognition principle by coupling with optical, electrochemical, or other transducer (signal transfer) [4] - [6]. However, the slower kinetics involved in molecular biological processes require stricter maintenance of the experimental protocol, e.g., the time of reaction between the antibody and the tracer molecule or analyte (hapten) should be set up in an exactly reproducible manner by means of flow-injection analysis 7],... 

Hapten monolayer electrode sensor assembly was used to detect triazine in a flow injection analysis mode. The interaction of the electrode with different antibody concentrations resulted in the formation of an antibody-antigen (Ab-Ag) complex which insulated the electrode towards the [Fe(CN)6] /Fe(CN)6] " redox probe and diis in turn resulted in no charge transfer. The extent of insulation depends on the antibody concentration and the time of exposure to the antibody solution. The decrease in amperometric response of the antigenic monolayer to corresponding antibody solution for a fixed time produces a quantitative measurement of the antibody concentration. Typical responses obtained for cyanazine-hapten monolayer electrode to different antibody concentrations is shown in Figure 4. The lowest detection limit achieved for cyanazine sensor was 4.0 pg/ml at a response time of few minutes and a less-than 2% cross-reactivity to atrazine, simazine and other metabolites. 

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