Sterilization is any process that removes, kills, or deactivates all forms of life. Sterilization is related to the term sterile, which means a complete absence of viable microorganisms or microbes that have the potential to reproduce. Thus, sterile products that undergo sterilization are often chemically or heat sterilized after being placed in their final packaging. The chemical or heat sterilization kills any microorganisms inside the products (obtained during manufacturing and packaging). This chemical or heat sterilization process after final product packaging is known as terminal sterilization. Show
What are ethylene oxide and sterilization by ethylene oxide?Ethylene oxide (EO) is a gas commonly used to sterilize medical devices and products chemically. Ethylene oxide is a potent and highly penetrating alkylating agent. These characteristics make it an extremely effective sterilizing agent. However, at certain levels, ethylene oxide is also capable of causing cancer. Sterilization by ethylene oxide kills microorganisms through exposure to ethylene oxide gas under vacuum and humidity. EO is used either as 100% EO or in combination with carbon dioxide. What items can be sterilized by ethylene oxide?Standard devices and materials sterilized with ethylene oxide are plastic materials (such as plastic devices), gowning materials, heat-labile equipment, and powders. Materials that can be moist heat sterilized can also be sterilized via ethylene oxide. However, if all materials in your device or product are easily sterilized via moist heat, moist heat is the cheaper and easier sterilization option. How is sterilization by ethylene oxide performed?A typical ethylene oxide sterilization cycle is shown in Figure 1. The exposure time for most EO sterilizations is relatively long (around 6 hours). The gas aeration period is also lengthy, up to 24 hours or more. After loading items into an ethylene oxide sterilization chamber, a vacuum is applied. Next, the chamber is filled to the desired relative humidity. Then an appropriate concentration of EO gas is added. Items undergoing sterilization rest in the EO gas under vacuum and humidity for the desired exposure time. Finally, the gas is slowly and safely evacuated from the EO sterilization chamber, and the sterilized items are given ample aeration time to support EO off-gassing. For sterilization validations, the D value of biological indicators used for EO sterilization validations may range up to 10-fold over the range of relative humidity values.  Factors that affect EO sterilization and lethality:
What are the problems with sterilization by EO?The primary issue with using ethylene oxide for sterilization is its absorption into certain materials and its reaction with water or other material components to form toxic residual compounds (ethylene oxide, ethylene glycol, and ethylene chlorhydrin). These residual compounds are hazardous both to people and to the environment. Ethylene glycol is formed from ethylene oxide and water reaction, while ethylene chlorhydrin is formed from the interaction of ethylene oxide and chloride compounds. Products sterilized with ethylene oxide must meet strict EO residual limits to keep patients safe during medical device and product use. Current ISO 10993-7 EO residual limits can be found here. Due to the toxicity of ethylene oxide residuals, both the occupational safety and health organization (OSHA) and the environmental protection agency (EPA) have threatened to ban EO use. However, radiation and pulsed light techniques are not robust enough to replace industrial EO use altogether. What are alternatives to ethylene oxide sterilization?Chlorine dioxide and vapor phase hydrogen peroxide (VPHP) are alternative gas sterilization agents. Surfaces of flexible and rigid barrier isolation systems can be sterilized with these gases. Ozone and peracetic acid are other alternative agents to EO. Ozone can be used for deionized water treatment and peracetic acid to sterilize isolators. Chloride dioxide sterilization cycles are shorter than EO cycles but still apply vacuum, humidity, gas exposure time, and aeration time, like EO cycles. Neither chloride dioxide nor VPHP can penetrate as readily as EO. However, chloride dioxide has superior penetration compared to VPHP. VPHP is the sterilant of choice for isolators because it is non-corrosive, requires relatively low temperatures (20–35◦C), is an effective sporicidal agent, and is environmentally friendly. SummaryOverall, sterilization by ethylene oxide is alternative to traditional heat sterilization methods. Ethylene oxide sterilization uses a combination of vacuum, humidity, temperature, and gas to sterilize materials at lower temperatures than dry heat or steam sterilization methods. While effective, ethylene oxide can result in toxic residuals. Thus, any ethylene oxide sterilized medical devices or products must undergo ethylene oxide residual testing to meet FDA requirements. All in all, ensure you choose a contract testing organization that can provide appropriate sterilization validations and ethylene oxide residual testing for your product needs. Like this article? Contact us for your next project Ethide Labs is a contract testing organization specializing in Sterilization Validations & Sterility Testing. Ethide Labs also offers EO Residual Testing, Microbiology Testing, Cytotoxicity Testing, Bacterial Endotoxin Testing, Bioburden Testing, Package Integrity Testing & Environmental Monitoring services for medical device companies and allied industries. Ethide is an ISO 13485 certified facility. ReferencesInternational Organization for Standardization. Sterilization of health care products- Moist heat- Part 1: Requirements for the development, validation, and routine control of a sterilization process for medical devices. Geneva (Switzerland): ISO; 2006. (ISO 17665-1:2006/(R)2016). Michael J. Akers. Sterile Drug Products Formulation, Packaging, Manufacture, and Quality. Drugs and the Pharmaceutical Sciences. Informa Healthcare. 2010. United States Pharmacopeial Convention. <1211> Sterility Assurance. Rockville, MD, USA. 2021. (USPC <1211>). What are the primary mechanisms of action of ethylene oxide gas as a sterilizing agent?Ethylene oxide is used for sterilization of critical items such as plastics, which cannot withstand high temperatures [14]. Owing to its nature as a gas, ethylene oxide penetrates well into the cell, reaching the DNA of the microorganism and killing it by alkylation.
How does ethylene oxide sterilization work?Ethylene Oxide Sterilization
Sterility occurs when an EO gas molecule reacts with and destroys the microbial DNA. The process requires the simultaneous control of four variables, but interdependent parameters: gas concentration, temperature, relative humidity, and time of exposure.
What is ethylene oxide gas sterilization?Ethylene Oxide (EtO) is an EPA-registered antimicrobial pesticide used to sterilize medical equipment and spices. It is the only sterilization method available for many medical devices and approximately 50 percent of all sterile medical devices in the United States are treated with EtO annually.
What is the mechanism of gaseous sterilization?Gaseous sterilization involves the process of exposing equipment or devices to different gases in a closed heated or pressurized chamber. Gaseous sterilization is a more effective technique as gases can pass through a tiny orifice and provide more effective results.
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