Material Selection and Management in Medical Devices

The selection of appropriate materials is a critical aspect of designing and manufacturing safe and effective medical devices. These materials fundamentally dictate a device's functionality, durability, and most importantly, its biocompatibility – its interaction with the human body.

Common Materials in Medical Devices

The diverse requirements of medical applications necessitate a wide range of material choices. Here are some common examples of materials used directly within medical devices:

Metals:
- Stainless Steel
- Titanium and its Alloys
- Cobalt-Chromium Alloys
- Nickel-Titanium Alloys (Nitinol)
Polymers:
- Polyvinyl Chloride (PVC)
- Polyethylene (PE)
- Silicones
- Polycarbonate (PC)
- Polytetrafluoroethylene (PTFE) – often used for coatings and lubricity
Ceramics
Composites

Beyond the device itself, specialized materials are also crucial for ensuring product integrity and sterility during storage and transport. Here are examples for product packaging:

PETG
Tyvek
Medical-Grade Papers
Foams
Polypropylene (PP)
Polycarbonate (PC)

Regulation of Materials in the International Medical Device Market

Unlike some other industries, there are few direct regulations that mandate the use of specific materials in medical devices. Instead, regulatory bodies worldwide impose stringent requirements on the safety, quality, and performance of finished medical devices, which inherently includes rigorous control over material selection and verification. The primary focus is on ensuring the materials used do not pose an unacceptable risk to patients or users.

European Union (EU) - Medical Device Regulation (MDR) (EU) 2017/745:

The EU MDR is a cornerstone regulation that significantly influences material selection and demands comprehensive verification. It mandates a holistic "life-cycle approach" to safety and performance.

Annex I: General Safety and Performance Requirements (GSPR)
- Section 10.4.1: Restricts Carcinogenic, Mutagenic, or Reprotoxic (CMR) and Endocrine-Disrupting Chemicals (EDCs) in materials. These substances are prohibited above 0.1% weight/weight in devices contacting the body or administered fluids, unless their presence is justified by a robust benefit-risk analysis.
- Section 16.1: Mandates biocompatibility testing for all materials contacting the human body, ensuring they do not compromise patient safety.

United States - Food and Drug Administration (FDA):

The FDA, as the primary regulatory authority for medical devices in the U.S., provides guidance on material safety, particularly through its:

Medical Device Material Safety Summaries [1]: While not regulations, these summaries offer insights into the FDA's current understanding of the performance and potential biological responses of commonly used implantable medical device materials.
Biocompatibility Guidance: The FDA extensively references and aligns with the ISO 10993 series of standards for the biological evaluation of medical devices.

Other Key International Regulations and Standards:

Packaging and Packaging Waste Regulation (EU): This is a "rising star" regulation directly impacting packaging materials, aiming to reduce packaging waste and promote circularity, which will increasingly influence material choices for medical device packaging.
International Standards (ISO):
- ISO 10993 series for biocompatibility: This comprehensive series is globally recognized and essential for evaluating the biological effects of medical device materials (e.g., cytotoxicity, sensitization, irritation, systemic toxicity, genotoxicity, implantation, hemocompatibility).
- ISO 11607-1:2020/A1:2023 – Packaging for terminally sterilized medical devices – Part 1: Requirements for materials, sterile barrier systems and packaging systems.
- ISO 11607-2:2020/A1:2023 – Packaging for terminally sterilized medical devices – Part 2: Validation requirements for forming, sealing and assembly processes.
Chemical Analysis for Biocompatibility Assessment (FDA Draft Guidance): This critical draft guidance, based on ISO 10993-18, provides detailed recommendations for chemical characterization of medical device materials as a key component of biocompatibility assessment.

Prominent Documentation for Materials

For materials to be qualified for use in medical devices or components, a robust documentation system is crucial. While materials themselves do not require MDR, MDSAP, or 510(k) clearance (as they have no single intended medical use), their suppliers should ideally hold ISO 9001 certification, or even better, ISO 13485 certification, to demonstrate adherence to quality management systems.

Documentation is generated by diverse stakeholders across the supply chain:

From Material Supplier:
- Material Specification
- Certificate of Conformance (CoC) / Certificate of Analysis (CoA)
- Material Safety Data Sheet (MSDS) / Safety Data Sheet (SDS)
From Component Supplier:
- Production Workflow
- Composition of different materials used in the component
- Quality Control of each LOT of critical material
- Change Control Records
From Legal Manufacturer (Finished Device):
- ROHS/REACH certificates (demonstrating compliance with restrictions on hazardous substances)
- Biocompatibility verification (for the device, including its materials)
- Packaging and Sterilization verification
- Material List (comprehensive list of all materials in the device)
- Physical, chemical, and functional verification of the final device

Typical Testing of Materials

For any material contacting the human body, biocompatibility testing is typically required. This includes, but is not limited to:

Cytotoxicity: Determines if the material causes cell death or inhibits cell growth.
Sensitization: Assesses the potential for allergic reactions.
Irritation: Evaluates localized inflammation or irritation.
Systemic toxicity: Examines if the material releases harmful substances into the body.
Genotoxicity: Evaluates potential for genetic damage.
Implantation: Assesses local effects after implantation (for implantable devices).
Hemocompatibility: Determines compatibility with blood (for blood-contacting devices).

Other essential testing, depending on the medical device's indication, includes:

Functionality: Evaluation of mechanical properties (e.g., strength, stiffness, hardness, wear resistance, fatigue life), flexibility, transparency, electrical conductivity, permeability, lubricity, and other performance characteristics.
Sterility of the whole medical device (if sterile).
Chemical Characterization: Identifying and quantifying extractable and leachable substances from the material.

What to Consider During Material Change

Material changes, even seemingly minor ones, can trigger significant regulatory hurdles. The primary challenge is to evaluate whether a new verification, such as biocompatibility testing (which can be costly), is required. Furthermore, a material change may prevent the manufacturer from producing the final medical device with the new material until a change registration or change notification is approved by the relevant authority in the target market.

Conversely, when a manufacturer has the choice for a new material, the keyword is "comparison to former material." This is particularly critical for materials of the medical device that have direct contact with the human body. Other materials, not in direct contact with the human body, should still be analyzed within the risk management system and documented in a change assessment.

Normally, to minimize regulatory effort, manufacturers should consider materials in the following rising order of risk:

Same chemical composition of material from the same or a new supplier.
Different but common chemical composition of material from a qualified supplier.
Different but common chemical composition of material from a new supplier.
New chemical composition of material from a qualified supplier.
New chemical composition of material from a new supplier.

The typical documents needed for a material change assessment are:

Material Specification
Certificate of Conformance (CoC) / Certificate of Analysis (CoA)
Material Safety Data Sheet (MSDS) / Safety Data Sheet (SDS)
Production Workflow
Change Control Records

Ideally, if the same supplier is used, a comparison table detailing the former and new material should be provided. This table significantly aids the change analysis by the manufacturer and facilitates review by critical international authorities.

What are PFAS?

Per- and polyfluoroalkyl substances (PFAS), often dubbed "forever chemicals" due to their exceptional persistence, have been widely utilized in medical devices for their unique properties such as chemical resistance, lubricity, and biocompatibility. These synthetic compounds are found in various components, including coatings for catheters and stents, orthopedic implants, and surgical instruments, enhancing durability and performance. However, growing concerns over their environmental persistence and potential links to adverse health effects are driving increasing regulatory scrutiny worldwide. Consequently, medical device manufacturers are actively exploring and developing PFAS-free alternatives to ensure compliance and mitigate future risks. The transition to new materials presents both challenges in maintaining device efficacy and opportunities for innovative, more sustainable solutions in medical technology.

How We Can Support

We can facilitate the qualification process between material or medical component suppliers and legal manufacturers, leveraging our in-depth experience.

Furthermore, our pathological experts can assist in the follow-up material analysis for verification. The most time and budget-consuming verification or validation activities can be executed in our partnership labs in Germany, China, and Malaysia.

Should a material change trigger international change registration, we can act as interim managers to oversee all regulatory tasks.