Autoradiography- All you need to know!

Autoradiography is a specialised imaging technique that uses radioactive sources contained in the sample exposed. In 1924, first biological experiment involving autoradiography traced the distribution of Holonium in biological specimens.

Principle of autoradiography

The principle of autoradiography is the precipitation of silver atoms, as a result of the ionization of a silver halide ie. AgX –  AgBr, AgCl, AgI or AgF) by radioactively labelled samples. They are usually suspended in a gelatin photographic emulsion. Once radioactive particles hit the gelatin emulsion, AgX is highly reduced producing insoluble silver crystals. Gelatin photographic emulsions are coated on photographic and X-ray films. When a radiolabeled sample is in contact with a coated X-ray film, it generates a hidden image in relation to the radioactivity distribution within the sample.

To make the image visible our eyes, the exposed photographic / X-ray film must be submerged in a special developing reagent, a chemical mixture that converts the silver crystals into shiny metallic silver. The gelatin emulsion is darkened. Silver nitrate (AgNO3) is highly efficient in the reduction of AgX molecules and is usually a component of developer solutions.

The reaction is then stopped by a fixative reagent, which removes the excess AgX from the photographic / X-ray film.

Types of Autoradiography

  1. In vivo autoradiography
  2. In vitro autoradiography

In both in vivo and in vitro autoradiography, the exposure of the radiolabeled sample to AgXcontaining photographic emulsion must always be performed in the dark (e.g., in a dark room, or in closed boxes).

Plant Life: Autoradiography

Applications of Autoradiography

1. To isolate the metabolic activity site in the cell.
2. To find the site and performance of the targeted drug.
3. To locate the metabolic activity site in the cell.
4. To find the site and performance of the targeted drug.
5. Tissue Location of a radioactive substance.
6. To find the location and amount of particular substances within a cell including cell organelle, metabolites etc,
7. To find and investigate the various properties of DNA.

Also check out, Autoradiography Application – YouTube

Did you read this- Cell Analogy to Human Body: Assignment – My Biology Dictionary

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