When it comes to sterilizing disposable medical devices, the choice of method is crucial. Among the most recognized processes are autoclaving (steam) sterilization, ethylene oxide (EtO) gas, and gamma irradiation. Selecting the appropriate sterilization process early in the development phase can significantly impact product safety and efficacy.
Gamma Irradiation Explained
Gamma irradiation sterilization involves exposing products to a radiation source, typically Cobalt-60. This isotope decays into Nickel-60, emitting gamma rays capable of penetrating the entire product and effectively deactivating microorganisms.
When designing a medical device, factors such as geometry, material composition, and construction must be carefully considered. For instance, one recent project involved a device made from various plastics, stainless steel, and adhesives, featuring long, narrow tubing that came into contact with therapeutic agents.
The Sterilization Process: Choosing the Right Method
Three primary sterilization processes stand out: autoclaving, ethylene oxide (EtO) gas, and gamma irradiation. Autoclaving utilizes high-pressure steam, which may not be compatible with certain plastics and adhesives. Similarly, the small diameter of the tubing in our recent device made it challenging for EtO gas to adequately reach and sterilize all surfaces.
Ultimately, gamma irradiation emerged as the most viable option. This method not only ensures thorough sterilization but also adheres to industry standards.
5 Tips for Preparing Your Product for Gamma Irradiation Sterilization
- Engage Early: Collaborate with a sterilization expert early in the design process. They can provide valuable guidance and recommendations tailored to your product’s needs. Attending webinars and consulting ISO 11137 can also familiarize you with essential terminology and the sterilization validation process.
- Establish Your Maximum Dose: Gamma irradiation is measured in kilo-Gray (kGy). Understanding the tolerance levels is essential; for example, to ensure a sterilization dose of 35 kGy, the delivered dose might range from 35 to 45 kGy. Ensure your product can withstand the maximum dose while still achieving sterilization. Targeting a maximum dose of 45-50 kGy typically allows for effective sterilization without compromising product integrity.
- Lock Down Your Design: Consistency in product design and materials is vital for effective sterilization. Changes in raw material suppliers can alter the bioburden (the presence of living microorganisms), which may require re-validation of the sterilization dose. Maintaining a stable supply chain minimizes costs and ensures a reliable sterilization process.
- Prepare a Regulatory Plan: Regulatory bodies, such as the MDR / FDA, will scrutinize your sterilization processes during approval. You must outline your sterilization method, the radiation dose, and the validation cycle plan. The VDmax25 method is often preferred for its reduced statistical sample requirements, while the sterility assurance level typically targets a 10^-6 probability of non-sterility.
- Execute and Validate: Once your product design is finalized, and materials are secured, it’s time for production. Pre-production units are excellent candidates for sterilization validation. The quantity will depend on your product’s complexity and the validation method chosen. For a tubing-based device, budgeting for 80-100 units for radiation dosing, analytical chemistry, and long-term shelf-life testing is advisable.
By following these steps and understanding the importance of gamma irradiation sterilization, you can ensure your medical devices meet the highest safety and efficacy standards.
