Gaseous sterilization using Ethylene oxide: It is gas at room temperature, highly inflammable & forms explosive mixture with air. This disadvantage can be overcome by using mixture of 10% ethylene oxide & 90 % carbon dioxide which is inert or halogenated hydrocarbon.
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 .
Advantages:
1) It is suitable for heat sensitive substances.
2) It is very reactive compound.
3) It has good penetration power.
4) The method is very reliable.
5) Method is useful for sterilization of mist sensitive substance and equipment because only low humidity is required.
Disadvantages:
• It is slow & more expensive.
• Control of relative humidity & hydration of organism is critical.
• IT is toxic & inflammable gas.
• Sophisticated instruments are required & skilled persons are needed.