Chemical gaseous method of sterilization

• Chemical gaseous sterilization is an effective method used to sterilize heat-sensitive materials that cannot withstand high temperatures or moisture.

• This method utilizes gases, such as ethylene oxide (EtO) and formaldehyde, to achieve sterilization by disrupting the DNA and protein structures of microorganisms.

• Below is a detailed study of the principle, procedure, merits, demerits, and applications of chemical gaseous sterilization.

Principle

• Chemical gaseous sterilization relies on the use of chemical vapors or gases that penetrate materials and react with cellular components, leading to the inactivation of microorganisms, including bacteria, viruses, fungi, and spores.

• The gases typically interfere with metabolic processes and nucleic acids, rendering the organisms non-viable.

Procedure

• The procedure varies slightly depending on the gas used, but generally follows these steps:

• Preparation:

  • Ensure materials are clean and dry.

  • Load the items into the sterilization chamber, ensuring proper arrangement for gas penetration.

• Sterilization Process:

  • Ethylene Oxide (EtO) Sterilization:

    • Preconditioning: Items may be preconditioned in a controlled environment to achieve the desired temperature and humidity.

    • Gas Exposure: The chamber is filled with EtO gas, often mixed with a diluent (e.g., CO2 or inert gases) to reduce flammability.

    • Exposure Time: Maintain the required concentration of gas for the specified time, usually ranging from 3 to 12 hours.

    • Aeration: Post-exposure, items are aerated to remove residual EtO, which can be toxic. This can take several hours to days, depending on the material and method used.

• Formaldehyde Sterilization:

  • Preparation: Generate formaldehyde gas using a solution of formalin and water.

  • Gas Exposure: The chamber is filled with formaldehyde gas at a concentration of around 8-16% at a controlled temperature and humidity.

  • Exposure Time: Typically, 2-4 hours.

  • Aeration: Allow sufficient aeration to remove any residual formaldehyde.

Monitoring:

• Use chemical indicators and biological indicators (e.g., spore strips) to ensure the effectiveness of the sterilization process.

Merits

1. Effective for Heat-Sensitive Materials: Ideal for sterilizing plastics, electronics, and other materials that cannot withstand high temperatures.

2. Penetration: Gases can penetrate porous materials and complex shapes, ensuring thorough sterilization.

3. Broad Spectrum: Effective against a wide range of microorganisms, including resistant spores.

4. Low Residual Activity: Residual gases can be eliminated through proper aeration, ensuring safe use of sterilized items.

Demerits

1. Toxicity: Gases like EtO and formaldehyde are toxic and carcinogenic, requiring careful handling and aeration.

2. Longer Sterilization Cycle: The process, including aeration, can be time-consuming.

3. Specialized Equipment: Requires specialized and often expensive equipment for proper gas handling and aeration.

4. Regulatory Compliance: Strict regulatory guidelines must be followed to ensure safety and efficacy.

Applications of sterilization

1. Medical Devices: Sterilization of complex and heat-sensitive medical instruments, such as endoscopes, catheters, and surgical kits.

2. Pharmaceuticals: Sterilization of drug packaging, syringes, and other pharmaceutical components.

3. Biological Materials: Sterilization of biological products, tissues, and other sensitive materials.

4. Electronics: Sterilization of electronic equipment and components that cannot tolerate heat or moisture.

5. Laboratory Supplies: Sterilization of labware, such as Petri dishes, pipettes, and filters that are sensitive to high temperatures.