What are the main features of EtO sterilization technology? What parameters are critical for its success?
Ethylene Oxide (EtO) as a sterilizing agent can be adopted when high temperatures and steam are not supported by the material to be processed. EtO sterilization is a simple, low-cost technology that has the ability to penetrate porous loads and is compatible with the vast majority of medical instruments, but due to its high toxicity, appropriate precautions must be taken.
This process requires the control of 4 parameters: EtO concentration (normally between 450 and 1200 mg/l), temperature (37°C to 63°C), time of exposure (depending on the cycle used) and relative humidity (from 40% to 80%). To understand the relevance of relative humidity (RH%) on EtO sterilization, it is necessary to know how this process works. The microbicidal activity of EtO is the result of alkylation (a chemical reaction) of proteins, DNA and RNA(1). This alkylation interferes with the normal cellular and reproductive processes, which renders a non-viability of affected microbes. Humidity plays a key role in EtO sterilization as it is a critical factor in alkylation chemical reactions and it is the most complex and difficult factor to determine because it influences the proper gas diffusion. Using RH% levels below the recommended lower limit will difficult the sterilization process, as alkylation reactions and proper gas distribution will NOT take place. On the other hand, when working in high percentages of RH (above the maximum recommended) water can (and will) condensate on the surface of the loads being sterilized. Water condensation on the surface function as a barrier for the EtO, hence the sterilization process will fail where condensation occurs. Therefore, it is mandatory to control the proper sterilization process by means of chemical and biological indicators.
At Terragene we offer different solutions for monitoring EtO sterilization processes, for further information visit:
(1) Shintani, H. (2017). Ethylene oxide gas sterilization of medical devices. Biocontrol science, 22(1), 1-16.