Radiation Method of Sterilization

• Radiation Method of Sterilization uses ionizing radiation to kill microorganisms.
• This method is highly effective and is commonly used for sterilizing medical devices, pharmaceuticals, and food products.

A) Ionizing Radiation Method of Sterilization

Principle

• Ionizing radiation (gamma rays, electron beams) generates free radicals that damage DNA and cellular components, leading to microbial death.

Types:

1. Gamma Rays:

   • Emitted from radioactive isotopes like Cobalt-60.

2. Electron Beams:

   • High-energy electrons generated by linear accelerators.

3. X-Rays:

   • Produced by x-ray machines at high voltages.

Procedure

1. Preparation:

   • Package items in radiation-permeable materials.
   • Use dosimeters to measure the absorbed dose.

2. Exposure:

   • Gamma: Place items around a Cobalt-60 source; exposure time varies by dose needed.
   • Electron Beam: Items pass under a beam, suitable for rapid processing.
   • X-Ray: Operates similarly to gamma irradiation but uses electrical generation.

3. Dosage:

   • Standard doses range from 15 to 25 kGy, based on microbial load and resistance.

4. Monitoring:

   • Biological indicators verify effectiveness, and dosimeters confirm accurate dose delivery.

Merits

1. Highly effective and penetrative.
2. Suitable for bulk sterilization.
3. No heat involved.

• Demerits

  • Requires specialized facilities.
  • Potential safety hazards due to radiation exposure.
  • Can alter material properties.

• Applications

  • Sterilization of medical supplies, pharmaceuticals, and food products.

B) Non-Ionizing Radiation Method of Sterilization (Ultraviolet Light)

Principle

• Ultraviolet (UV) radiation, particularly UV-C (200-280 nm), causes the formation of thymine dimers in DNA, inhibiting replication and transcription, leading to cell death.

Procedure

1. UV Source:

   • Lamps: Low-pressure mercury lamps (254 nm).
   • LEDs: Emerging option with specific wavelengths.

2. Exposure:

   • Surface Sterilization: Place items within 1 meter; exposure time varies (typically minutes).
   • Air/Water: UV lamps used in HVAC systems or water treatment units.

3. Safety Precautions:

   • Protection: Use UV-blocking goggles and skin protection.
   • Interlocks: Safety switches prevent accidental exposure.

4. Limitations:

   • Line of Sight: Only sterilizes directly exposed surfaces.
   • Distance: Effectiveness reduces with increased distance or obstructions.

Merits

• Effective for surface sterilization.
• Immediate action.
• No chemical residues.

Demerits

• Limited to surface sterilization.
• UV light can degrade plastics and other materials.
• Hazardous to eyes and skin.

Applications

• Sterilization of laboratory workspaces, air, and water purification

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