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Renin Angiotensin Mechanism.

Sterilization by Radiation.

 

Introduction:

  • Definition: Sterilization is defined as complete removal of microorganisms from an object, surface or a product.

  • Sterilization by radiation uses radiations for sterilization.

  • This method is also called “Cold Sterilization” as there is very negligible amount of heat production during the process.

  • It is further divided into Ionizing and Nonionizing Radiations.

Ionizing Radiation

  • X-ray and gamma rays are the commonly used ionizing radiation for sterilization.

  • These are high energy radiation which causes ionization of various substances along with water.

  • The ionization results in the formation of a large number of toxic O2 metabolites like hydroxyl radical, superoxide ion, and H2O2 through ionization of water.

  • These metabolites are highly oxidizing agents and kill microorganisms by oxidizing various cellular components.

  • With ionizing radiation, microbial resistance decreases with the presence of moisture or dissolved oxygen (as a result of increased free radical production) and also with elevated temperatures.

  • Radiation sterilization is generally exposed to items in the dried state which include surgical instruments, sutures, prostheses, unit-dose ointments, plastic syringes, and dry pharmaceutical products.

Ultraviolet (non-ionizing) radiation

  • Ultraviolet radiation includes light rays from 150-3900 Å, of which 2600 Å has the highest bactericidal effect.

  • Non-ionizing waves have a very little penetration power, so microorganisms only on the surface are killed.

  • Upon exposure, these waves are absorbed by many materials, particularly nucleic acids.

  • The waves, as a result, cause the formation of pyrimidine dimers which bring error in DNA replication and cause the death of microbes by mutation.

  • UV radiation owing to its poor penetrability of conventional packaging materials is unsuitable for sterilization of pharmaceutical dosage forms.

  • It is, however, applied in the sterilization of air, for the surface sterilization of aseptic work areas, and the treatment of manufacturing-grade water.
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