Immunoassay versatility

The versatility of luminescence goes beyond intensity-, wavelength- and kinetic-based measurements. Fluorescence polarization (or anisotropy) is an additional parameter still largely unexplored for optical sensing yet widely used in Biochemistry to study the interaction of proteins, the microfluidity of cell membranes and in fluorescence immunoassays. Although only a few optosensors based on luminescence polarization measurements can be found in the literature, elegant devices have recently been reported to measure chemical parameters such as pFI or O2 even with the bare eye41. 

In conclusion, ECL should continue to have a promising future in analytical science. The versatility of Ru(bpy)32+ ECL will continue to be exploited for an increasingly diverse range of analytical determinations, especially in biomedical applications and immunoassay. Inevitably, for all but the most simple sample... 

Schweitzer, B., Wiltshire, S., Lamber, J., O Malley, S., Kukanskis, K., Zhu, Z., Kingsmore, S.E, Lizardi, F.M., and Ward, D.C., Immunoassays with rolling circle DNA amplification a versatile platform for ultrasensitive antigen detection, Proc. Natl. Acad. Sci. USA, 97, 10113-10119, 2000. 

In heterogeneous assays the bound and free label forms must be separated by different means, such as precipitation of antibody or coupling of the antibody to a solid support. Heterogeneous immunoassays are more versatile as inclusion of a separation step eliminates most of the interferences before quantification. However, these assays are also more labor-intensive and time-consuming. Any of these methods can be performed in either competitive or non-competitive format. 

The 4-parameter logistic model is considered the most versatile one for fitting the dose-response curves in immunoassays [42]. The fitting equation is given by [22, 23, 41]... 

Enzymes are perhaps the most versatile and popular class of labeling substrates for IAs and they have a sure future in this field [64, 65]. They were introduced in 1971 as an alternative to isotopes in immunoassays [66]. 

The role of the immunoassay, especially the radioimmunoassay (RIA), in clinical biochemistry has been the major factor in the tremendous advances made in that field since its introduction in 1959 (11). At present the RIA is the most powerful analytical tool available for quantitative detection of molecules of diverse structure and function in biological fluids of human, animal and now plant origin. The immunoassay comprises a unique combination of sensitivity and specificity as well as precision and applicability. With this assay technique, it is now possible to detect and very accurately measure compounds at endogenous physiological concentrations which frequently are in the range of 10 M or lower. In Table II the major characteristics of the immunoassay are listed. This method is versatile, specific, can be utilized for almost an unlimited number of compounds and has a high throughput potential. 

Schweitzer B, Wiltshire S, Lambert J, O Malley S, Kukanskis K, Zhu Z, Kingsmore SF, Lizardi PM, Ward DC. Immunoassays with rolling circle DNA amplification A versatile platform for ultrasensitive antigen detection. Proc Natl Acad Sci USA 2000 97(18) 10113—10119. 

Immunoassays are very versatile, and if one could select but a single method, it could be the method of choice. Fortunately we have a variety of techniques available and a good analyst should know when to apply them. Table I provides some general rules for determining how difficult an immunoassay will be. The terms used are relative and possibly other dimensions to the table could be the laboratory s experience with immunoassay and the problems faced. This table does not indicate that good assays cannot be developed for hard compounds it just Indicates that the expense, skill and time required may be greater for those compounds. For instance we have developed successful immunoassays for some lipophilic, small, unstable, volatile compounds. However, such compounds would be a poor choice to use for one s first venture into immunoassay development. 

Immunoassay is an application of the substoichiometric principle ( 9.3.4) developed by Yalow (Nobel laureate in 1977) for protein analysis. In the United States tens of millions radioimmunoassays are made annually in hospitals to measure hormones, enzymes, viruses, serum proteins, drugs, and so forth. Only a drop of the patient s blood is needed, reflecting the versatility and smisitivity of this technique, which can be performed automatically. Commercial RAST-kits (Radio Allergy Sorbent Tests) are used for rapid diagnosis of allergic reactions. 

The versatility and nature of immunoassays allow the detection of virtually any type of compound. The reliability of these detection methods is assessed by validation studies, although they are not always easy to carry out, due to the nature of the analyte and the lack of reference materials. These assays are used by food industry and regulatory agencies for different purposes. Immunoassays can be used by the food industry... 

Time-resolved fluorometry is versatile in its application. Applied in immunoassay, time-resolved fluorometry presents an unmatched combination of advantages. While sensitive and specific, radioimmunoassays present safety and stability problems. While safe, enzyme immunoassays lack sensitivity and dynamic range. 

The development of a rapid on-site immunoassay system with a versatile and easy to use handheld meter provides an objective means of screening for levels of agricultural and environmental chemicals in either a remote site or laboratory setting and will enable Iretter monitoring of the levels and movement of chemicals through the environment. 

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