|
Mr. Amit Srivastava
DGM, Board of Radiation and Isotope Technology, ISOMED,
Mumbai |
Definition: Radiation
is form of energy coming out from the matter.
Types of Radiation:1.
Ionizing Radiation Ex: α, β, γ, neutron 2. Non-Ionizing
Radiation Ex: visible light, IR, Microwave, etc. 1.
Directly Ionizing Radiation: α and β 2. Indirectly
Ionizing Radiation: γ and neutron
Penetration power of different radiation
Major Interaction of gamma radiation with matter -
Compton effect
Effects of Ionizing Radiation on living cell
Ionizing radiation can modify physical, chemical and
biological properties of the living cell by:
• Free radicals production
• Breaking of chemical bonds
• Producing new chemical bonds and cross-linkage between
macromolecules (polymer)
• DNA modification and damage or death of living cells
• Living cells contain more than 70% water
• Livings cells contain DNA, cell membrane, mitochondria
etc.
• Radiolysis of water generates free radicals in cells
causing DNA alteration or damage, ultimately leading to
cell death.
• This process is used for sterilization of health care
products. |
Water radiolysis (Ionization of water molecules due
to radiation)
H2O H°, eaq, OH°, H2, H2O2
Radiolysis: breaking of chemical bond by
radiation. Free Radical: Atoms of molecules having
single unpaired electron (H° ,OH° )
DNA-Damage by gamma radiation
Effects of Ionizing Radiation on material
• Organic materials are more susceptible to
radiation (polymers – cross linking degradation) due to
their nature of atomic bonding.
• Metals are less susceptible to radiation
(Reason - metallic bonding)
• Major change in the property of metals caused by
Radiation is due to defects on atomic level (Schotty
and Frenkel)
Methods of Sterilization
• Sun Drying,
• Steam sterilization,
• ETO and
• Ionising Radiation (gamma and e-beam)
Preservation by Sun Drying (Old Method)
 . |
