Enzyme modulator mediated immunoassay (EMMIA)

The digoxigenin:anti-digoxigenin (DIG) technology--a survey on the concept and realization of a novel bioanalytical indicator system

A review is given on the novel non-radioactive digoxigenin:anti-digoxigenin (DIG) bioanalytical indicator system. After a general introduction on direct and indirect indicator systems based on previous non-radioactive indicator reactions as well as in vitro and in vivo amplification procedures the principle of the new digoxigenin:anti-digoxigenin technology is demonstrated. The novel system is based on the specific high-affinity interaction between the cardenolide digoxigenin from Digitalis plants and a digoxigenin-specific antibody coupled with a reporter group. A variety of methods for digoxigenin modification of nucleic acids, proteins and glycans are presented. In addition, various applications of the novel non-radioactive indicator system in a variety of direct or indirect detection approaches with either insoluble or soluble substrates are described. It is also shown that with these applications alternative reaction formats are used which are partly characterized by additional amplification steps.

Development and clinical application of sensitive enzyme immunoassay for macromolecular antigens--a review

Radioimmunoassay has been a powerful tool to measure haptens and antigens which are important for the investigation and diagnosis of diseases, especially endocrine disorders. However, the use of radioisotopes in radioimmunoassay suffers from serious disadvantages. Radioisotope-labeled reagents are unstable and hazardous to health. The disposal of radioactive wastes is not easy. Furthermore, the sensitivity of radioimmunoassay is limited by the detection limit of radioisotope that depends upon the half-life. The detection limit of the most widely used radioisotope, 125I, with a half-life of 60 days is 5 to 10 amol, when it is carrier-free. By contrast, the use of enzymes has obvious advantages. Some enzymes are very stable and cause no health hazards or waste disposal problems, provided that appropriate substrates are chosen. The detection limits of some enzymes are lower than that of 125I and will be further improved in the future. Therefore, enzyme immunoassay is potentially more sensitive than radioimmunoassay. This article reviews the development and clinical application of sensitive enzyme immunoassay for macromolecular antigens, which has been replacing radioimmunoassay.