Sensitization Test – Evaluation of Biocompatibility in Accordance with EN ISO 10993-10
Medical devices can trigger not only a physical reaction but also an immunological reaction upon contact with the human body.
One such reaction is sensitization, in which the body develops an allergic reaction to the chemical substances or material components contained in the product. The sensitization test—EN ISO 10993-10— is an internationally recognized standard for assessing whether medical devices can trigger such allergic reactions.
EN ISO 10993-10 is titled “Biological Evaluation of Medical Devices—Part 10: Tests for Skin Sensitization.” This standard defines the methods used to determine whether delayed hypersensitivity reactions (Type IV hypersensitivity) occur upon skin contact with the product or when it is applied to the body. For MDR (2017/745) and FDA 510(k) submissions, this test must be conducted in accordance with GLP (Good Laboratory Practice) principles.
What is sensitization, and why is it tested?
Sensitization is the process by which the immune system develops a “memory” for a substance after the body’s first exposure to it and triggers a severe allergic reaction upon subsequent exposure. This reaction typically manifests as skin redness, swelling, itching, and eczema. Substances in medical devices that can trigger such reactions include:
- Plasticizers and stabilizers: phthalates, epoxy resins
- Metal alloys: nickel, cobalt, chromium
- Latex and rubber components: Natural latex proteins, vulcanization accelerators
- Adhesives and Coatings: Acrylates, Formaldehyde Resins
- Sterilization Residues: Ethylene Oxide Residues
The sensitization test scientifically determines whether the product releases these substances into the body through the skin or systemically, and whether it triggers an allergic reaction. Before the test is conducted, a chemical characterization of the product (ISO 10993-18) is performed to identify which substances may be released.
Sensitization testing procedures
EN ISO 10993-10 recommends three main methods for evaluating sensitization. The choice of method depends on the intended use of the product, the duration of contact, and the properties of the extract being tested.
1. GPMT (Guinea Pig Maximization Test)
This is the most commonly used method and is considered the gold standard. The test is performed on guinea pigs using a combination of intradermal injection and topical application. The test substance is mixed with the complete Freund’s adjuvant (FCA) to enhance the immune system’s response. After the induction phase, the test substance is administered to the animals again (challenge phase), and the skin reactions are evaluated.
2. Buehler Test (closed patch test)
It was developed as an alternative to the GPMT. In this method, the test substance is applied to the guinea pigs' skin in the form of a closed patch. No injection is used. It is particularly suitable for products intended for topical use and highly concentrated extracts.
3. LLNA (Local Lymph Node Assay)
In this method, which is performed on mice, cell proliferation (multiplication) in the ear lymph nodes is measured using radioactive tracers or bioluminescence techniques to determine sensitization potential. Because it better aligns with the 3R principles (Replacement, Reduction, Refinement), it is increasingly preferred today. However, it may not be suitable for some device extracts.
Comparison of Sensitization Test Methods
The following table summarizes the sensitization test methods used in accordance with EN ISO 10993-10:
| Method | Animal model | Form of Use | Advantages | Disadvantages |
|---|---|---|---|---|
| GPMT | Guinea Pig | Intradermal injection + topical patch | High sensitivity, gold standard, widely recognized | Requires more animals; takes a long time (~30 days) |
| Buehler Test | Guinea Pig | Occlusive dressing (topical) | No injection required; suitable for topical use | The sensitivity may be lower than that of the GPMT |
| LLNA | Mouse | Topical (ear skin) | Fewer animals, 3R-compliant, quantitative results | Use of radioactive substances (in some versions); not suitable for certain substances |
How does the sensitization test procedure work?
Conducting an immunoprophylaxis test for a medical device requires a meticulous procedure. This process is designed to reflect the product’s clinical conditions of use:
- 1. Sample Preparation and Extraction: The product is extracted using polar and nonpolar solvents in accordance with ISO 10993-12. This process transfers chemicals that could be released from the medical device into the solution.
- 2. Dose Determination: The concentration of the extract is calculated based on the clinical dose and the surface area of the medical device.
- 3. Induction phase: The test substance is administered to the animals according to the selected method. This phase ensures that the immune system becomes sensitized to the substance.
- 4. Challenge phase: After a specified period of time, the test substance is administered again in a low concentration.
- 5. Monitoring and Evaluation: Skin reactions (erythema and edema) are assessed at 24, 48, and 72 hours. Evaluation is based on the Magnusson and Kligman scales.
- 6. Reporting: The results are documented in accordance with GLP standards. It is indicated whether the product has sensitizing potential.
GLP-Compliant Sensitization Testing Services with Nano-Test
The biocompatibility assessment of your medical device requires not only test results but also documentation of a quality that meets the requirements of regulatory authorities. Nano-Test is your reliable partner in this process, offering GLP-compliant sensitization tests in accordance with EN ISO 10993-10.
Nano-Test – Statement of Work
Nano-Test offers sensitization tests for medical devices in accordance with EN ISO 10993-10. In our preclinical laboratories, which are accredited according to GLP (Good Laboratory Practice) and ISO/IEC 17025, we use the GPMT (Grouped Maximum Number of Test Animals) test, the Buehler test, and the LLNA (Local Lymph Node Assay).
Our service process includes ISO 10993-12-compliant extraction of your product, dose optimization, in vivo testing phases, and histopathological evaluations. All work is performed in compliance with the approvals of the ethics committees for laboratory animals and under veterinary supervision. The results are provided as GLP-compliant reports with full traceability, which you can use for your MDR and FDA 510(k) submissions.
At Nano-Test, we not only conduct tests, but also assist you in developing your biocompatibility strategy (Biological Evaluation Plan—BEP) and provide you with robust data for your communications with regulatory authorities.
Advantages of Nano-Test's sensitization test:
- Comprehensive selection of methods: All methods—GPMT, Buehler, and LLNA—are available.
- GLP-certified infrastructure: All studies are conducted in accordance with GLP principles and ALCOA+ requirements.
- Rapid Planning: The most appropriate testing strategy is determined based on the device category and contact time.
- Expert veterinary team: The welfare of laboratory animals and ethical standards are upheld at the highest level.
- Compliance with the 3R Principles: Whenever possible, methods such as LLNA that require fewer animals are recommended.
Sensitization is one of the most common and troublesome adverse reactions that can be caused by medical devices.
Sensitization testing— EN ISO 10993-10 —is a crucial step in scientifically determining whether your product poses this risk. Selecting the correct test method, properly performing the extraction, and reporting the results in accordance with GLP standards are prerequisites for a smooth regulatory approval process.
With its preclinical infrastructure, specialized staff, and GLP-compliant processes, Nano-Test fully meets the requirements of medical device manufacturers for sensitization testing. Partner with Nano-Test to enhance the safety of your product and accelerate market access.