Competitive inhibition immunoassay

Polycarbonate compact discs have also been used as supports for microarray development [112]. The microarray is generated using an inkjet applicator that employs an electric current to dispense monodisperse droplets containing antibodies onto the disk. The sensing reaction is based on competitive inhibition immunoassays using fluorescent antibodies and final readout is accomplished using a fluorescence scanner. 

Hunter, K. W., and Lenz, D. E. (1982). Detection and quantitation of the orgiinophosphatc pesticide paraoxon by competitive inhibition immunoassay. Life Set. 30, 355-361,... 

Pentachlorophenol. The evaluation of an immunoassay kit for the determination of pentachlorophenol (PCP) residues in water (IS) was carried out in conjunction with the current gas chromatography/electron capture detection procedure. The kit is based on a monoclonal antibody-based competitive inhibition Immunoassay and has a shelf-life of about one year. (CP is the second most heavily used pesticide in the USA. In Canada, it is registered as a wood preservative, insecticide and herbicide with the sodium salt of (CP often being used as a general disinfectant for trays in mushroom houses and wood preservative in crates. Since toxic pesticides of this type can pollute streams and ground water, it is necessary to monitor its presence. 

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. 

Competitive Inhibition in the Enzyme-Immunoassay with Purified Polyethers Including Ciguatoxin. Figure 2 represents an inhibition curve in the competitive test between a positive fish tissue and highly purified CTX (LD = 0.25 yg/kg mouse) in suspension. Approximately 0.002 ng of purified ciguatoxin gave 50% inhibition of the normal binding between sheep anti-CTX and the toxic fish tissue (Lutj anus sp.). 

The analysis of fish tissues for ciguatoxin by a newly developed enzyme-immunoassay procedure (26, 27) has been carried out in this study. Three areas of examinations have been attempted (1) the examination of clinically defined and documented and non-toxic consumed fish samples (2) the assessment of freshly caught fishes from the sites in the Leeward part of the island of Oahu where ciguatoxin is found and (3) competitive inhibition with suspension of purified ciguatoxin and closely related structurally similar polyether toxins. 

The ELISA tests are performed using different incubation steps, depending on the assay format, namely sandwich, competitive or inhibition immunoassays that correspond to the way the analyte is captured and further revealed, which is generally dictated by the nature of the analyte. 

The theoretical concepts related to the idiotypic network and the nature of molecular mimicry are important areas of immunological research (34-37). Although the intricacies of the natural process are complex, several practical applications of anti-idiotypic antibodies to biological problems have been made, e.g. to detect and isolate certain receptors. The competitive inhibition by ligands of the idiotype-anti-idiotype interaction will also enable the environmental scientist to develop novel immunoassay procedures for compounds of interest. Two specific antibodies are required. The idiotype (Abl), specific for the hapten, is obtained by... 

Table II shows that all derivatives of endosulfan (except endosulfanlactone in the competitive-type immunoassay) exhibited a significant affinity to the antiserum. However, there were major differences in the amount of crossreaction in the assay types, e.g., endosulfandiol was better recognized in the competitive-type immunoassay than in the inhibition-type assay. A possible reason for these differences may be that in one case the antibodies were immobilized and the binding of these antibodies to the solid phase could have an effect on the avidity.

Competitive enzyme immunoassays with antigen immobilized on the solid phase This technique is based on the inhibition... 

Hunter, K.W., Lenz, D.E., Brimfield, A.A., and Naylor, J.A., Quantification of the organophosphorous nerve agent soman by competitive inhibition enzyme immunoassay using monoclonal antibodies, FEES Lett, 149, 147, 1982. 

The procedures for production of specific antibodies and their application in a competitive inhibition ELISA (Enzyme-Linked Immunosorbent Assay) are discussed in detail in the preceding chapter (Vanderlaan et al., this volume). In addition, other comprehensive overviews of the immunoassay development process in the pesticide field are available in general, a... 

The evaluation of a number of immunoassay diagnostic kits was undertaken to determine their usefulness in a regulatory analytical laboratory environment in the food, feed and pesticide areas. Four rapid enzyme immunoassay tests for the detection of aflatoxin residues at the 20 ppb level in animal feeds were compared to the official HPLC procedure. In the pesticide area, a commercial pentachlorophenol competitive inhibition assay for residues in water was investigated as to its applicability to poultry and pork liver matrices. In addition, an ELISA screening procedure for the herbicide fusilade was developed. Modifications were incorporated into the rapid immunoband 1-2 Test procedure for the detection of motile Salmonella in various food and animal feed products resulting in quicker analysis than the standard culture method. Also, a comparative evaluation of a Quik-Card Test for sulphamethazine drug residues in pork urine, liver and muscle tissue, is described. 

Figure 4. Effect of acetaminophen-conjugate substituents on antibody recognition in the acetaminophen-adduct immunoassay. The decrease in inhibition due to particular substituents is shown. These values were calculated by comparing the ability of the following acetaminophen-conjugate analogs to competitively inhibit antibody binding to solid-phase acetaminophen-bound metallothionein. a N-acetyl-L-cysteine compared to 3-(N-acetyl-L-cystein-S-yl)acetaminophen. b acetaminophen compared to 3-(N-acetyl-L-cystein-S-yl)acetaminophen. c 2-(N-acetyl-L-cystein-S-yl)hydroquinone compared to 3-(N-acetyl-L-cystein-S-yD-acetaminophen. d 3-(methylthio)acetanilide compared to 3-(methyl-thiolacetaminophen. e 2-(L-cystein-S-yl)-2-aminophenol compared to 3-(L-cystein-S-ylacetaminophen. f 3-(L-cystein-S-yl)acetaminophen compared to 3-(N-acetyl-L-cystein-S-yl)acetaminophen. g 3-(methyl-thiolacetaminophen compared to 3-(N-acetyl-L-cystein-S-yD-acetaminophen (Reproduced fimm Ref. 14).

Hokama Y, Kimura LH, Abad MA, Yokochi L, Scheuer PJ, Nukina M, Yasumoto T, Baden DG, Shimizu Y (1984) An enzyme immunoassay for the detection of ciguatoxin and competitive inhibitions of related natural polyethers toxins. In Seafood Toxins. Ragelis EP (ed), ACS Symposium Series 262, p 307-320. 

The testosterone enzyme immunoassay was a solid phase double antibody competitive inhibition assay with horseradish peroxidase linked to testosterone-3-CMO. The testosterone antiserum was generated in rabbits against 4-androsten-ll-a-17-p-diol-3-one-ll-hemisuccinate bovine serum albumin. Cross reaction of the antiserum was as follows 17-p-hydroxyl-4,6-androstandien-3-one (60%), 5-a-androstan-17-p-ol-3-one (52%), 19-... 

The most common of these systems is the enzyme-multiplied immunoassay technique or EMIT, which is particularly suited to the measurement of small molecules (haptens) such as drugs. EMIT is a trade mark of the Syva Corporation of Palo Alto, California. Although it does not involve the separation of bound fraction from free it is nevertheless a competitive assay system. The antigen is labelled with an enzyme in such a way that the enzyme retains its catalytic activity. When the antigen binds to the antibody the enzyme becomes inhibited, probably by an induced conformational change or by steric hindrance of the enzyme active site (Figure 7.15). 

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