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
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
Highly effective and penetrative.
Suitable for bulk sterilization.
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 (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.