BY- Ezhuthachan Mithu Mohanan (MSIWM043)

It is a bioanalytical technique. Autoradiography is used for the detection of components or materials that have radioactive properties. The film obtained is known as autoradiograph. Radioactive materials can emit ionizing radiation or particles. Using X-ray, relative bands on gels can be obtained by radioactive emission. The first emission of autoradiography was observed in 1867, when accidentally emulsion of AgCl and iodide, turned black by uranium. In World War II, the advent of photographic emulsions and photographic films was used. The first biology experiment which used autoradiography was traced back in 1924, to find polonium distribution. Now in biological techniques the detection of radioactive substances or radioactive isotopes using autoradiography.

Mechanism: Activation of silver present in emulsion causes the penetration of negatively charged beta particles emitted by radioactive salts using silver halide film emission. Unstable activated silver crystals reduce to black silver particles, which are then detected. The most suitable temperature is 70°C. preflashing improves the quality and sensitivity. It requires one hit per crystal. Pre Flashing is mostly done before use.

Types of radiation:

There are mainly three types of radiations used: 

1) Alpha rays:  Particles with 2 neutrons and 2 protons. Source: Radium226

2) Beta rays: when electrons are emitted by nuclei. Two type hard beta and soft beta.

3) Gamma rays: electromagnetic rays. Gamma emitter: CO60 

Autoradiography in various counters: 

Steps of autoradiography:

Fluorography: 

To increase sensitivity of autoradiography, fluorography can be used. Fluorography transfer radioactive emission into light which is easily transmitted through film. Phosphor compounds can be used in Fluorography.

Advantages Disadvantages
Easy to handleChances of misinterpretation with binding sites
Highly specificNon physiological significance
Localize receptorsNon- specificity of ligands
Can be applied to different kind of tissues

Factors for efficiency of autoradiography:

Emitter energy: most suitable energy of radiation is beta emitting isotopes , having energy between γ and α radiation

 Distance and thickness of sample: very thick and far distance can cause the lose of radiation

Amount of silver halide crystals:  less concentration of gelatin, and smaller grain sixe

Emulsion thickness: thickness depends on emitters.

Exposure time: long time cause much high and clear pattern.

Application:

  1. Used for determination and localization of receptors.
  2. To obtain various properties of DNA
  3. To study oxidative phosphorylation
  4. Photosynthesis
  5. Used for electrophoretic transfer of proteins
  6. Used in cytogenesis
  7. Used in radiopharmaceutical research
  8.  Used in virology as radioimmuno-electro-osmophoresis
  9.  Imaging and analysing rock
  10. Used in MALDI-MS
  11. Secondary ion mass spectrophotometry
  12. Whole body imaging
  13. Genetic studies
  14. Comparison of complex mixture of proteins
  15. In microbial ecology
  16. Used for study of foliar nutrients.

Conclusion:

Used for detection of different target receptors. It provide as a tool for better understanding of molecular science and pharmacology. Also used for genetic engineering.

References: 

  1. Autoradiography-Types-of-Radiations-Used-and-Measuring-Autoradiography-1115 @ http://www.biotecharticles.com. (n.d.). https://www.biotecharticles.com/Biology-Article/Autoradiography-Types-of-Radiations-Used-and-Measuring-Autoradiography-1115.html#:~:text=The following three types of,ejected or emitted by nuclei.
  2. Tabassum Khan, N. (2017). Autoradiography: Detection and Analysis of Radioactive Entities. Journal of Biometrics & Biostatistics, 08(04), 8–9. https://doi.org/10.4172/2155-6180.1000361

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