Biocompatibility And Material Selection – How To Retain Efficiency In The Design Process

By Ian Matthews, Owen Mumford

For medical devices, user safety is paramount. Any material within a device that could contact the patient at any time must demonstrate biocompatibility – that is, it must not cause any form of adverse reaction to the user. However, there are different biocompatibility requirements (or endpoints) that must be demonstrated, depending on the duration and the nature of patient contact.

For devices that must make contact with or penetrate the skin to deliver medication or treatment, further testing and toxicological evaluation is required to ensure that device materials do not affect health or cause irritation. Per regulatory requirement, the test results and material evaluation must prove that the finished device, including its entire manufacturing process, demonstrates biocompatibility.

Understanding The Manufacturing, Testing, And Evaluation Process For Biocompatibility

The international standard for device testing, ISO 10993, provides guidance on how medical devices can be tested as part of a wider risk management and risk-reduction strategy. For manufacturers and their partners, knowledge of the testing and assessment processes can help ensure that new devices are developed to meet biocompatibility needs, as well as internal development timescales.

By factoring the need for biocompatibility from the conceptual phase of the project, product development teams can determine quickly which assessment methods are required to demonstrate biocompatibility. Utilizing previous experience concerning the chemical properties of manufactured components, and knowing which materials can and cannot be used, reduces potential challenges further down the development cycle. Ideally, a full database of biocompatible materials can be consulted, which will lower the risk of biocompatibility failure in the chosen components.

Without this material awareness, an incorrect combination of materials could be used in the proposed device, or any of a range of irritants could be added as part of the manufacturing or assembly process. Just one oversight can cause failure in biocompatibility testing, and thus lengthen the product development cycle.

Challenges For Biocompatibility

As with any project, the customer will have specific requirements they would like to see met. However, maintaining the ability to optimise product capabilities against potential material restrictions can be challenging, and has a significant impact on development time. Customer requirements often result in conflicting functional characteristics, which require further research and development or a compromise in product specification to continue.

Biocompatibility assessments and toxicology evaluations are significant challenges when developing a commercial device within a strict time frame. These biological evaluations do not result in a definitive pass or fail; the information gathered forms part of a risk-based analysis, which either determines acceptability or recommends further testing to demonstrate all biological endpoints. The level of assessment, toxicology, and completed testing must be comprehensive and well-documented to ensure there is no ambiguity or other causes for concern during the device’s regulatory submission.

The U.S. Food and Drug Administration (FDA) guidance on meeting the needs of ISO 10993, published in June 2016, points to the biocompatibility assessment process covering “the material components, the manufacturing processes, the clinical use of the device including the intended anatomical location, and the frequency and duration of exposure.”

Identifying potential risks can help streamline the overall development process for medical device manufacturers and a cumulative, comprehensive level of internal understanding can prove to be extremely valuable over time. For example, when working with a third-party organization that doesn’t have a detailed background in the required manufacturing components for medical devices, simple things like the selection of product colors or method of component ejection from a tool can lead to significant additional testing requirements.

That said, if a new color or a change to the manufacturing process is essential to the success of the new device, then additional testing and toxicology evaluations must be incorporated into the product development timeline. With novel materials, toxicologists can explore the chemical characterisation of each component to determine if any risk exists, informing the design phase of the project. With any material, the overall evaluation must be completed on both production-representative materials and the proposed manufacturing process.

While the added testing may add to product development timelines, the delay can be offset by harnessing experience and historical data. Still, pressure to deliver on client requests as part of overall design requirements can be high, so maintaining the ability to deliver new product capabilities and innovation while remaining compliant with all relevant regulations can be a balancing act.

Designing For Biocompatibility More Efficiently

When developing a new medical device, it’s important to understand precisely how patients will make use of the device during their treatment plans: “Where?” “When?” ” How often?” “Among whom?” — all of these are relevant questions. Patient/consumer usage patterns can affect biocompatibility, particularly among devices that will have prolonged contact with the patient’s body.

This vetting process includes looking at how device components are affected over a period of use — for example, examining in situ polymerising or elements that could be absorbed by the patient’s body over time. The FDA recommends testing medical devices throughout development, and test articles can be created for biological testing to demonstrate how materials break down over time. Chemical characterisation is an important technique used to demonstrate this material degradation.

Based on these requirements, a company’s design process must evolve over time, in terms of both efficiency and material characteristic understanding, so that the most appropriate materials are used to meet product requirements and biocompatibility needs. For example, maintaining a database of materials to document testing and toxicology evaluation is essential to inform the selection of materials and provide a record of historical data.

Similarly, plaque testing can demonstrate the suitability of materials before part geometry is defined. By creating small plaques of material that can be manufactured using the same process intended for final production devices, materials can be tested and their biological properties understood.

Existing materials hold great potential for greater efficiency in product design, while new materials can provide devices with improved functional, manufacturing, or commercial advantages. Understanding the whole design process enables manufacturers to better determine when it’s advantageous to invest in testing and chemical evaluation of new materials for biocompatibility, and when existing materials can achieve the desired results.

About the author

Ian Matthews is a design engineering team manager at Owen Mumford. He holds a BSc in industrial design. He has worked in the medical device industry for five years, at Owen Mumford and ResMed - and also has six years of industry experience at Dyson and BMW. His current role manages detailed design development of injection products, ensuring all design inputs are achieved to a high quality standard.

About Owen Mumford 

Owen Mumford is a major medical device manufacturer that develops pioneering medical devices for its own Owen Mumford brand and custom device solutions for the world’s major pharmaceutical and diagnostic companies. To learn more, visit Owen Mumford on Facebook, Twitter, and LinkedIn.