Some important medical devices are required for sterilization but are not possible through heat sterilization due to damage to the materials. In such cases, gaseous sterilization is required. Like Plastic syringes, blood transfusion apparatus, plastic pipettes, Petri dishes, etc. The main gaseous agents used for sterilization are ethylene oxide, formaldehyde, beta-propiolactone, etc. They act on the principle of denaturing proteins and DNA by cross-linking functional groups. But this method has some disadvantages.
Disadvantages:
• Gas can be hazardous to people.
• They are often highly explosive.
• Sometimes gases are extremely poisonous.
• They are potentially carcinogenic.
Factors affecting gaseous sterilization:
• The efficiency of the sterilization method is influenced
by the concentration of ethylene oxide.
• The humidity of the sterilizing atmosphere.
• The temperature of sterilization.
• Time of exposure.
• Physical nature and permeability of the load.
• Atmospheric preconditioning of the load before
sterilization.
Formaldehyde: It is also a group of alkylating agents.
It inactivates microorganisms by alkylating the amino acid and sulfhydryl
groups of proteins and ring nitrogen atoms of purine bases. It is a gaseous
disinfectant and biocide. It is a strong, broad-spectrum disinfectant and
biocide that can kill bacteria, viruses, fungi, and endospores. It is very
irritating to living tissues and also carcinogenic, therefore it is not used as
an antiseptic.
Ethylene Oxides: It is a type of alkylating agent
that is used for gaseous sterilization. It is highly penetrating and can
sterilize items within plastic bags such as catheters, and disposable items in
laboratories and clinical settings.
• It is gaseous above 10.8°C.
• Ethylene oxide has high antimicrobial activity, it kills
even endospores.
• It is used for the sterilization of heat-sensitive
materials such as spices, oils, plastics, etc.
• Ethylene oxide is used in formulation with CO2
as Freon (CClFe).
β-Propiolactone: It binds to DNA, thereby
inactivating it. It is a clear liquid with a strong odor and can kill
endospores. It has been used in either liquid form or as a vapor for the
sterilization of medical instruments and tissue grafts, and it is a common
component of vaccines, used to maintain their sterility. It is also used for
the sterilization of nutrient broth, as well as blood plasma, milk, and water.
• It is gas above 15.5°C.
• Penetration power of β-propiolactone is less than ethylene
oxide but it is more active in killing microorganisms.
• Due to its carcinogenic effects, it is not commonly used.
Applications of Gaseous Sterilization:
• This method is used for sterilizing thermolabile
substances like hormones, proteins, various heat-sensitive drugs, etc.