by Radioimmunoassay
Radioimmunoassay (RIA) is an analytical technique used for detecting and quantifying substances in biological samples. It utilizes the principle of competitive binding between a labeled antigen and an unlabeled antigen in the presence of a limited quantity of antibody. RIA is highly sensitive and can detect and measure substances that are present in minuscule quantities. This technique has revolutionized clinical chemistry and biomedical research since its introduction in 1960.
How does Radioimmunoassay Work?
In Radioimmunoassay, the antigen whose concentration needs to be measured is labeled with a radioactive atom. This radiolabeled antigen competes with the unlabeled antigen present in the test sample for the binding sites on specific antibodies. After allowing sufficient time for binding, the antibody-bound radiolabeled and unlabeled antigens are separated, usually through precipitation. The amount of bound radioactivity is measured, which is inversely proportional to the concentration of unlabeled antigen present in the sample. The higher the amount of unlabeled antigen, lesser will be the binding of radiolabeled antigen to antibody. By using standards of known concentrations of unlabeled antigen, a calibration curve is generated from which the concentration of unlabeled antigen in the test sample can be derived.
Components Required for Radioimmunoassay
There are four main components required to perform an RIA:
1. Radiolabeled antigen: The antigen whose concentration needs to be measured is labeled with a radioactive isotope such as iodine-125 or tritium.
2. Unlabeled antigen: This is the antigen present in the test sample and competes with the radiolabeled antigen for antibody binding.
3. Specific antibody: Antibodies are raised in animals against the unlabeled antigen. The antibodies specifically bind the antigen.
4. Separation system: To separate the antibody-bound radiolabeled and unlabeled antigen from the unbound antigens. Precipitation with second antibody or charcoal and resin methods are commonly used.
Applications of Radioimmunoassay
Due to its high sensitivity and accuracy, RIA has numerous clinical and research applications. Some major uses are:
1. Hormone assays: RIA is extensively used for detecting and quantifying hormones such as insulin, thyroid hormones, cortisol etc. in blood or other body fluids.
2. Therapeutic drug monitoring: Levels of drugs administered for treatment like digoxin, phenytoin can be accurately monitored through RIA.
3. Oncology: Tumor markers like cancer antigen (CA) 125, CA 19-9 are measured by RIA to diagnose and monitor cancer.
4. Endocrinology: RIA helps in diagnosis of endocrine disorders like hypothyroidism, Cushing’s syndrome.
5. Pharmacokinetics: Absorption, distribution, metabolism and excretion of drugs can be studied through RIA by measuring drug levels over time.
6. Nutritional studies: Vitamins and minerals are estimated in RIA for assessing nutritional status.
7. Biomedical research: RIA has vastly advanced research in fields like reproductive biology, neuroendocrinology through quantitative analysis.
Advantages of Radioimmunoassay
Some key advantages of RIA include:
– Extremely high sensitivity – Can detect down to picograms or even femtograms of antigen quantity.
– Highly specific – Uses specific antibodies to detect precise antigen without any interference.
– Versatility – Can quantify numerous substances ranging from small molecules to large proteins.
– Applicable to various samples – Be it serum, plasma, urine or tissue homogenates.
– Reproducible results – Assays can be reproduced easily in any standard laboratory.
– Relatively simple procedure – Basic chemistry laboratory is sufficient to perform RIA after standardization.
– Low cost analysis – Approximately $2-5 per test making it economical for analyzing large number of samples.
radioimmunoassay has revolutionized biochemical measurements due to high sensitivity, specificity, reproducibility and low cost. It has become an indispensable tool for clinical diagnostics, pharmacokinetic studies, biomedical research and more. Development of non-radioactive alternatives like enzyme-linked immunosorbent assay have further enhanced the versatility of immunoassays. RIA techniques continue to evolve with technological advancements for accurate quantification of molecular targets.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
Ravina Pandya, a content writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemicals and materials, etc. With an MBA in E-commerce, she has expertise in SEO-optimized content that resonates with industry professionals.
