radioimmunoassay

Basic principles:

In the radioimmunoassay experiment, excessive labeled antigen *Ag and unlabeled antigen Ag (i.e. antigen to be detected) compete with a small amount of antibody (Ab) for binding.

If the radioactivity of the conjugate (*Ag-Ab) is high, it means that the concentration of analyte is low.

If the radioactivity of the conjugate is low, it means that the concentration of analyte is high. By analyzing the standard curve, the concentration of the object to be measured can be calculated.

1960, American scholars Yarrow and Belson established radioimmunoassay, which was first used to determine the insulin content in plasma of diabetic patients. This is a major breakthrough of China's laws in the fields of medicine and biology, and has opened a new era in the history of medical laboratory. It enables substances that were originally considered too small to be measured and have important biological significance to be accurately quantified, thus opening up a new road for further uncovering the mystery of life and making it possible for people to re-understand the biochemical and physiological basis of some life phenomena at the molecular level. In the following 30 years, the rapid progress of endocrine science fully proved the great impetus of this ultra-micro analysis technology. 1977, the inventor of this technology won the Nobel Prize in Biomedicine. Then this brand-new technology quickly penetrated into other fields of medical science, such as virology, pharmacology, hematology, immunology, forensic medicine, oncology, and other disciplines related to medical biology, such as agricultural science, ecology and environmental science. The substances of radioimmunoassay have expanded from hormones to almost all bioactive substances. Our research on radioimmunoassay began in 1962, and it developed and popularized rapidly, which greatly promoted the progress of biomedicine in China. (A) the advantages of RIA

Radioimmunoassay has many incomparable advantages over other analytical methods. It not only has high specificity of immune reaction, but also has high sensitivity of radioactive measurement, so it can accurately determine all kinds of extremely small substances with immune activity.

1. The detection limit of general chemical analysis methods with high sensitivity is 10 ~ 10g, while RIA is usually 10 (nanogram, ng), 10g (pique, pg), or even 10g (.

2. Strong specificity Because the specificity of antigen-antibody immune reaction is very strong, the object to be detected must be the corresponding antigen. Good specific antibodies can recognize substances with very similar chemical structures, and even recognize stereoisomers.

3. Widely used According to incomplete statistics, at least 300 bioactive substances have established RIA. It can be applied to the analysis of almost all hormones (including peptides and sterols), as well as protein, tumor antigens, virus antigens, bacterial antigens, parasite antigens, and some small molecules (such as cyclic nucleotides) and drugs (such as digoxin and digitalis glycosides), and its application scope is still expanding. In recent years, due to the great development of antibody preparation technology with small molecular haptens, it is expected that almost all bioactive substances, as long as their content is not lower than the detection limit of RIA, can establish suitable RIA methods.

4. Simple operation. RIA doesn't need many kinds of reagents, so it can be made into a kit. The sample adding procedure is simple, a large number of samples can be analyzed at one time, and the sample consumption is also small; The reaction time is not long; Measurement and data processing are easy to realize automation; RIA is an in vitro analytical technique, which has no radiation hazard to patients.

(B) the shortcomings of RIA

1. Immune reaction can only detect substances with immune activity, but bioactive substances without immune activity can't be detected. Therefore, RIA results may be inconsistent with bioassay results.

2. Because of the use of biochemical reagents, its stability is affected by many factors, and a set of quality control measures is needed to ensure the reliability of the results.

3. Sensitivity is limited by the working principle of the method itself, and some substances with extremely low content in the body cannot be determined.

4. Because radioimmunoassay is a competitive reaction, neither the tested substance nor the standard substance can participate in the reaction, and the measured value is a relative quantity rather than an absolute quantity.

5. There are problems such as radiation and pollution.

Although RIA has the above shortcomings, it is an advanced technology of quantitative analysis method after all. With the progress of science and technology, radioimmunoassay technology will be developed more widely and deeply.