The type (or modality) of sterilization used for a medical device can impact the materials chosen for the sterile barrier system. Therefore, as a packaging engineer, it’s important to understand what sterilization is, the different types of sterilization, and why it is important.
Sterilization is a process in which microorganisms are eliminated from a medical device in a timely and efficient way. Eliminating these microorganisms is important as it prevents the transmission of disease in association with the device. With most single-use medical devices, sterilization is a necessary step in the commercialization process.
In the medical device packaging industry, we often use the term “terminally sterilized”. Terminal sterilization is the process of sterilizing a product in its final packaging. As stated in ISO 11607, the goal of a terminally sterilized medical device packaging system is to allow sterilization, provide physical protection, maintain sterility up to the point of use, and allow aseptic presentation. The sterilization process can add harsh stress and strain to a sterile barrier system, so it’s important to understand as much as possible about each modality.
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There are three main groups of sterilization modalities: Chemical, Radiation, and Heat.
Chemical: Traditionally, this has been the most popular sterilization modality, specifically Ethylene Oxide (EO). The reason for its popularity is that it’s effective at killing microbes, is readily available, has been around for decades, and is compatible with many types of materials. NO2 and VHP are two examples of alternative innovative chemical sterilization modalities that offer many of the same benefits as EO. However, these innovative modalities are still being assessed to determine compatibility with packaging materials.
Radiation: The three main types of radiation sterilization are Gamma, E-Beam and X-ray, with Gamma currently being the most common. Radiation can cause some medical device packaging materials to become stiff and brittle and may affect performance. It is also important to avoid cellulose-based materials such as medical grade paper as radiation sterilization can cause discoloration.
Heat: Sterilization using heat is typically delivered in two ways: moist heat (steam) or dry heat. There are limitations with the selection of sterile barrier system materials used, since the elevated temperature can reactivate some or all of a package’s seal or cause other issues such as film delamination. Moist heat sterilization is commonly performed by a hospital in an autoclave on medical devices or equipment designed for reuse. However, there are some sterile barrier packaging materials specifically designed for compatibility with moist and dry heat sterilization that can be used for single use devices.
Regardless of sterilization type, there will always be some level of impact to sterile barrier systems that, as the packaging engineer, you should become familiar with. A trusted resource for compatibility of materials with these and other sterilization modalities is AAMI TIR 17 “Compatibility of Materials Subject to Sterilization”. This knowledge ensures you can plan appropriately when making recommendations on materials and packaging design.
Let’s use EO as an example of what a packaging engineer would need to consider when determining packaging design and materials. EO requires a porous substrate within the sterile barrier system to effectively sterilize the packaged device. Materials that are porous and compatible with EO sterilization are Tyvek® or medical grade paper. It is important to not only design your sterile barrier system with a porous substrate, but also to ensure that the porosity is not obstructed by a label or by design of the final packaging configuration. This obstruction could cause issues for the sterile barrier system within the EO sterilization cycle and could lead to packaging defects such as seal creep.
The role of packaging in sterilization is to create a sterile barrier system that allows for sterilization and maintains the sterile barrier until to the point of use. A key to success is to protect the sterile barrier system and device from the hazards associated with the sterilization process. My advice to packaging engineers is to remember that while it is not up to you to select the sterilization modality, it’s important that you are a part of the conversation. Talking with your sterilization colleagues early in the process to understand the requirements and associated hazards will help you design your packaging system successfully.
