Discuss in brief about gaseous sterilization.
Gaseous sterilization using Ethylene oxide:
Ethylene oxide:
It is colourless gas at room temperature.
It can be liquefied easily and boil at 10.80C.
It is highly inflammable so it us used in mixture form:
Ethylene oxide 1 part + carbon dioxide 9 part.
Ethylene oxide 11% w/v part + Trichlofluromethane 79% w/w + dichlorodiflurometane 10%w/w
Ethylene oxide 12%w/w + dichlorodifluromethane 88%w/w.
Sterilization is done in a chamber which can be heated to the desired degree of temperature.
The material is to be sterilized is packed in chamber and treated with Ethylene oxide gas.
Sterilization in absence if air:
It is carried out in a evacuated sterilizer at sub atmospheric pressure with Ethylene oxide 90% + carbon dioxide 10%.
Advantages:
1. High penetration.
2. Can maintained high conc.
3. Very reactive.
4. Non Irritant to respiratory tract.
5. Used for heat sensitive material.
6. Used for sterilization of moist –sensitive material.
Disadvantages:
Method very slow.
Cost is high.
Apparatus very expensive.
It is highly inflammable.
Certain toxic substance produced such as ethylene chlorohydrins.
Mechanism of action:
Ethylene oxide exerts its lethal effect on microorganisms by alkylation essential metabolites. The alkylation probably occurs by replacing an active hydrogen on sulphahydral, amino, carboxyl, hydroxy group in enzymes ,proteins & nucleic acids
Method:
• The sterilization is done in pressure chamber which is designed in such a way to give controlled temp., humidity, gas conc. & exposure time.
• The material to be sterilized is first exposed to high humidity of about 98% leading to humidification of organism.
• Then it is exposed to sterilizing gas. ( fuming ethylene oxide ) under pressure till desired concentration is obtained.
• Exposure period may range from 6-24 hrs depending upon degree of contamination & penetrability of material .
• Others gases used are formaldehyde and Beta-propiolactone.