Ionizing radiation can effectively sterilize organisms without increasing temperature through mechanisms like producing reactive molecules that damage DNA and proteins. X-rays, gamma rays, and electron beams are common sources of ionizing radiation used for sterilization. X-rays have advantages like deeper penetration and faster processing compared to gamma rays and electron beams. Gamma rays also effectively sterilize through breaking down DNA, and are used for sterilizing medical devices and foods. UV light is another sterilization method using UVC wavelengths to damage nucleic acids and disrupt DNA/RNA of microbes. It is effective against bacteria and viruses and used for sterilizing air, water, and surfaces.

1. RADIATION
M.Meenakshi.
Assistant Professor,
Dept of Microbiology,
Sri Ramakrishna College of Arts & Science for Women,
Coimbatore

6. IONIZING RADIATIONS
 Ionizing radiation is an excellent agent for sterilization/disinfection, it kills organisms
without increasing the temperature; so aptly called cold sterilization. It destroys bacterial
endospore and vegetative cells, both eukaryotic and prokaryotic; but not always effective
against viruses.
 Mechanism of Sterilization by Ionizing Radiations
 When ionizing radiation collides with particles, they produce electrons (e−) and other
reactive molecules such as hydroxyl radicals (•OH), and hydride radicals (H•). Each of
these reactive molecules is capable of degrading and altering biopolymers such as DNA
and protein. Breakage of DNA and degradation of enzymes lead to the death of the
irradiated cells.
 Several sources of ionizing radiation are available, including X-ray machines, cathode ray
tubes (electron-beam radiation), and radioactive nuclides (sources of gamma/x-rays).

8. X RAYS

9.  Sterilization is used for killing unwanted microorganisms in medical devices, healthcare
products, pharmaceuticals and combination drug devices.
 The X-rays are high-energy, high-frequency, short-wavelength electromagnetic photons. This
allows for X-ray sterilization to offer the best features of gamma and E-beam
 X-ray sterilization offers better penetration characteristics than either gamma or E-beam.
 The X-rays deeper penetration allows for this technique to be used on many products and
packaging configurations that E-beam cannot.
 X-rays are able be used on products made of all types of materials including metals, liquids
and high-density and multicomponent products
 . In addition, the deeper penetration allow for larger packaging configurations and pallets to
be sterilized as well.
 X-ray sterilization offers one of the fastest processing times of any sterilization technique. I
X-rays

11. ADVANTAGES
 With its advantages over almost all other current sterilization techniques, X-ray
sterilization is the up and coming sterilization technique and warrants your
consideration both for new products and for transition of current products.
 Already included in international standards and FDA guidelines, the usage of X-ray
sterilization is already approved by regulatory bodies.

13. GAMMA RAYS
 Gamma irradiation is a physical/chemical means
of sterilization, because it kills bacteria by
breaking down bacterial DNA, inhibiting
bacterial division. Energy of gamma rays passes
through the equipment, disrupting the
pathogens that cause contamination
Gamma radiation is created by the decomposition of an atom

14. GAMMA RAYS
 Gamma irradiation is a physical/chemical means of sterilization, because it kills bacteria
by breaking down bacterial DNA, inhibiting bacterial division.
 Energy of gamma rays passes through the equipment, disrupting the pathogens that
cause contamination.
 These changes at the molecular level cause the death of contaminating organisms or
render such organisms incapable of reproduction.
 The gamma irradiation process does not create residuals or impart radioactivity in the
processed items.
 Complete penetration can be achieved depending on the thickness of the material

15. APPLICATIONS
 Sterilization by radiation is also used for sterilization of plastic syringes, hypodermic needles,
scalpels, surgical blades, adhesive dressings and thermolabile medicaments.
 Other applications include: syringes, surgical gloves, gowns, masks, sticking plasters,
dressings, ‘tetrapacks,’ bottle teats for premature babies, food packaging, raw materials for
pharmaceuticals and cosmetics, and even wine corks.
 Another common application of sterilization by Gamma irradiation is food. Food sterilization
by gamma irradiation is the process of exposing food to ionizing radiation to destroy
microorganisms, namely bacteria, or insects that might be present in the food.

16. ADVANTAGES & DISADVANTAGES
 Advantages- Gamma rays have a high penetration power so materials can be
sterilized after filling them in the final container
 The method is suitable for all types of materials such as dry, moist and even frozen
items
 The method is considered to be reliable and can be accurately controlled
 Disadvantages
 There is some risk involved since exposure to radiation may be harmful to workers
 It can produce undesirable changes in medicine such as color, solubility and texture of
the product
 It can actually damage the material it’s meant to sterilize
 It’s expensive

17. UV light

18. UV STERILIZATION
 Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-
wavelength ultraviolet (ultraviolet C or UV-C) light to kill or
activate microorganisms by destroying nucleic acids and disrupting their DNA,
leaving them unable to perform vital cellular functions
 UV light has been used for sterilization and disinfection as early as the mid-20th
century. With advancements in technology, and specifically in the UV bulbs
themselves, its reliable long lifespan (thousands-of-hours) and smaller size (e.g.
UV LED vs traditional UV bulbs) has broadened the field for where it can be
used.
 You can find it being used to disinfect: water, air, fruits, vegetables, surgical
utensils, tablet computers, toys and a variety of surfaces

19. UV
 UV is divided into three types with reducing wavelengths and increasing energy. They are
UVA, UVB and UVC. For UV sterilization, only UVC (100-280nm) has high enough energy to
effectively kill microorganisms.
 When you are shopping for a UV sterilization product to try in your home or business, make
sure that its UV wavelength falls in the range of UVC (100-280 nm).
 Studies have shown that UVC at 254 nm is effective against all foodborne pathogens, natural
microbiota, molds, and yeasts. Because microorganisms come with different sizes and shapes
that affect their UV absorption, the required time for killing each species varies.2

20. MECHANISM
 UV sterilization also known as UV disinfection or ultraviolet germicidal irradiation
(UVGI) works by breaking down certain chemical bonds and scrambling the
structure of DNA, RNA and proteins, causing a microorganism to be unable to
multiply.
 When a microorganism is unable to multiply, it is considered dead since it cannot
reproduce within a host and is no longer infectious

21. Examples…
 if you use a UV lamp held within 1 inch above a petri dish grown with E. coli, it
will only take 1-2 min to show a complete sterilization.1 For sterilizing surgical
instruments in a medium UV box, it might take 5-10 min.
 For sterilizing an 8-foot biosafety cabinet in a lab, a common recommendation is
30 min.

22. MECHANISM
 limitation of UV sterilization is that UVC causes so much damage in both proteins
and DNA/RNA that they cannot be used for biomedical products.
 For example, UVC sterilization of viruses causes so much damage to the viruses’
surface proteins that they cannot be used as vaccines to induce proper immune
responses.
 A different kind of “UV inactivation” method is used in biomedical products to
preserve viral surface proteins while effectively inactivating viruses.
 This is also the method we use for our UV inactivated purified virus products
because we want to use the intact viral proteins of the UV treated viruses for
biomedical use such as generating antibodies.

23. UV

24. USES
 UV-C light is weak at the Earth's surface since the ozone layer of the atmosphere blocks
it.[2] UVGI devices can produce strong enough UV-C light in circulating air or water systems
to make them inhospitable environments to microorganisms such
as bacteria, viruses, molds, and other pathogens. UVGI can be coupled with a filtration
system to sanitize air and water.
 The application of UVGI to disinfection has been an accepted practice since the mid-20th
century. It has been used primarily in medical sanitation and sterile work facilities.
Increasingly, it has been employed to sterilize drinking and wastewater since the holding
facilities are enclosed and can be circulated to ensure a higher exposure to the UV. UVGI has
found renewed application in air purifiers

25. UV
 UV light is electromagnetic radiation with wavelengths shorter than visible
light but longer than X-rays. UV is categorised into several wavelength ranges,
with short-wavelength UV (UV-C) considered "germicidal UV".
 Wavelengths between about 200 nm and 300 nm are strongly absorbed by nucleic
acids.
 The absorbed energy can result in defects including pyrimidine dimers.
 These dimers can prevent replication or can prevent the expression of necessary
proteins, resulting in the death or inactivation of the organism.

26. UV
 Mercury-based lamps operating at low vapor pressure emit UV light at the 253.7 nm line.[8]
 Ultraviolet light-emitting diode (UV-C LED) lamps emit UV light at selectable wavelengths between
255 and 280 nm.[9]
 Pulsed-xenon lamps emit UV light across the entire UV spectrum with a peak emission near 230 nm
 This process is similar to the effect of longer wavelengths (UV-B) producing sunburn in humans.
Microorganisms have less protection against UV and cannot survive prolonged exposure to it.
 A UVGI system is designed to expose environments such as water tanks, sealed rooms and forced air
systems to germicidal UV.
 Exposure comes from germicidal lamps that emit germicidal UV at the correct wavelength, thus
irradiating the environment.
 The forced flow of air or water through this environment ensures exposure.

27. INACTIVATION OF MICROORGANISM
 The degree of inactivation by ultraviolet radiation is directly related to the UV dose
applied to the water.
 The dosage, a product of UV light intensity and exposure time, is usually measured
in microjoules per square centimeter, or equivalently as microwatt seconds per
square centimeter (μW·s/cm2).
 Dosages for a 90% kill of most bacteria and viruses range between 2,000 and
8,000 μW·s/cm2.
 Larger parasites such as cryptosporidium require a lower dose for inactivation. As a
result, the U.S. Environmental Protection Agency has accepted UV disinfection as a
method for drinking water plants to obtain cryptosporidium, giardia or virus
inactivation credits.
 For example, for a 90% reduction of cryptosporidium, a minimum dose of
2,500 μW·s/cm2 is required based on the U.S. EPA UV Guidance Manual published
in 2006.

28. REFERENCES
 https://tuttnauer.com/blog/sterilization-by-gamma-irradiation
 https://www.rpi.edu/dept/chem-eng/Biotech-
Environ/Projects00/sterilize/radiation.html
 https://www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/other-
methods.html
 http://hps.org/publicinformation/ate/faqs/whatisradiation.html

29. THANK YOU