The importance of a sterilization process and toxicology in sterile barrier system selection

In the first part of selecting a sterile barrier system, we delved into various considerations such as the packaging method and the selection criteria for the packaging materials. It follows that choosing the right medical package depends on understanding the effect that materials and sterilization processes have on one another.

As described in ISO 11607:2019 (Annex A), the selection of sterile packaging materials in packaging system design for a medical device must consider the relationship between the device’s features and the sealing and sterilization processes. A sterile barrier system and the protective packaging should maintain sterility while exposed to expected conditions and hazards during specific processing, storage, and distribution up to the point of use. At the same time, it must allow for aseptic presentation.  

In this article, we focus on how the sterilization process and toxicological properties affect the choice of packaging materials.

Sterilization process

• materials must have appropriate levels of cleanliness, particulate matter, and lint; 
• materials must meet established specific or minimum mechanical properties (e.g., tensile strength, thickness variation, tear resistance, air permeance, and burst strength); 
• materials must meet established specific chemical properties (e.g., pH value, chloride, and sulfate content) to meet the requirements of the medical device, packaging system, and sterilization process; and 
• materials must meet acceptance criteria for microbial barrier properties, unless they already meet certain impermeability criteria as defined in ISO 11607 Annex C.

 (* More testing methods for microbial barrier systems can be found in ISO/TS 17665)

Regarding materials compatibility with the sterilization process, there are several aspects that need to be considered, including:

• Verification that the materials and pre-formed sterile barrier system are compatible with the intended sterilization method. 
• A check of the sterilization equipment to determine that it is designed and operated according to national or international standards that ensure sterilization compatibility. (e.g., ANSI/AAMI ST79, ISO 11135, ISO 11137, ISO 14937, EN285, EN13060, EN1422, EN14180)
• Verification that the material can maintain its sterility and ability under specific conditions for a particular sterilization process. 
• Consideration that the materials can be resistant to multiple sterilization processes depending on whether the same or different sterilization process was used. 
• A check of the ability of the material to set different specifications according to the properties of the inner and outer layers when the device needs a multilayer packaginge. 
• Verification that the compatibility of the sterile barrier system and validation of the sterilization process can be concurrent. 
• Verification that the chemical indicator (CI*) printed on the package should be no less than 100mm2, and the printing should not affect the sealing process.

(* CI printing should follow the requirements of EN/ISO 11140-1) Ensuring compliance with performance testing as per ISO 11607 Annex D — that the sealing strength should not be less than 1.5N/15mm either before or after the sterilization process. Moreover, that the wet strength of sealing should not be less than 1.2N/15mm either before or after steam or EO sterilization.

Toxicological properties

According to the biocompatibility evaluation of ISO 1093-1, packaging materials and their components should not react with a medical device to cause pollution, or transfer any substance that would have an adverse effect on the medical device. As for what is required of the material, it must be free of taste and not affect the performance and safety of the medical device that it will pack.   

All in all, choosing the appropriate packaging method and materials for the sterilization type are key elements in developing an effective sterile barrier system. However, the sealing process also directly affects the sterility of the sterile barrier system and the packaging validation test. Therefore, it is important to understand how these individual requirements affect each other and to maintain clear communications between medical device manufacturers, packaging materials suppliers, and sterilization providers.

Understandably, compliance with ISO 11607 and keeping pace with changes in the medical packaging industry is fraught with challenges. At SIGMA, we are committed to partnering with our customers to produce ever-improving medical sterile barrier systems that meet evolving regulatory requirements.