If you missed our post introducing commonly overlooked sterilization considerations for medical device packaging, check it out here. If you’ve been waiting for this week’s mini class on Gamma Sterilization and its packaging considerations, let’s get started.
GAMMA STERILIZATION SCIENCE
Gamma rays are one of three naturally occurring types of radioactivity. They are the only form that occurs as rays, sharing the stage with alpha and beta particles. Gamma is the most energetic form of electromagnetic radiation, with a very short wavelength of less than a nanometer.
The PCL lab frequently sees medical devices sterilized using gamma irradiation. In fact, it has been a go-to standard sterilization method for most medical devices over the past 40 years.* The gamma sterilization process deploys gamma radiation in the form of Cobalt 60** and an electron beam. Together, they pass through plastics and other materials, killing microorganisms quickly and effectively.
To perform gamma sterilization, the medical device, sealed in its final packaged state, passes through the gamma irradiation on a conveyor belt, effectively sterilizing the device. The gamma process can affect both porous and non-porous packaging materials. Resulting molecular stress during gamma irradiation can morph packaging into a high-risk state. Potential negative gamma effects include:
Many materials are at risk for visual degradation during gamma irradiation. Plastics, for example, may change from clear to gold. Opacity and gloss can also be affected.
Radiation can embrittle plastics and other materials, putting them at risk for densification or a “burnt” or fragile feel.
SEAL and STERILE BARRIER CHANGES
Seal strength and adhesion can deteriorate during gamma sterilization. This is caused by the heat created by many bouncing electrons during the process. In some instances, however, gamma radiation can actually strengthen seals. Proper material selection and validations ensure compatibility with the gamma method.
WILL YOUR PACKAGING SURVIVE GAMMA?
Knowing how your packaging materials will handle gamma sterilization is vital to ensure the optimal look and feel not only for aesthetics, but from safety, compliance and end-user confidence perspectives. These considerations should be included in every medical device development timeline, with a medical-device-specific engineer engaged as early as possible.
If PCL is engineering packaging for a gamma sterilized product, we run feasibility testing on multiple material and packaging configurations to confirm the integrity and optimal performance. Regardless of who is handling your packaging engineering, it pays to have these tests built into your timeline from an ISO 17025 accredited lab. A combined schedule of gamma irradiation testing with integrity testing gives the benefit of detailed material performance data for physical characteristics and sterile barrier integrity. If a negative event occurs, you’ve contained it at testing phase before putting your product at risk. Other beneficial tests include visual inspection, Bubble Leak (ASTM F2096) and Peel Test (ASTM F88).
For anyone who’d like to take a deeper dive, we’ve included a couple additional resources here
Refer to AAMI TIR 17 to learn more about the compatibility of materials subjected to sterilization.
Put aside your ISO 11607 and check out the ISO 11137 for details on radiation sterilization validation.
Our third sterilization school session will be up next week! We’re always happy to answer questions at any stage of your project, so feel free to reach out. Call, live chat or use our contact form at the bottom of this post. See you soon.
* Int J Med Sci. 2018; 15(3): 274–279.
** Cobalt 60 is an unstable atom containing excess nuclear energy called a “radionuclide.”