Sensitization Testing (ISO 10993-10)
Evaluate the allergenic potential of your medical device using the GPMT, Buehler, or LLNA methods.
Sensitization (delayed-type hypersensitivity) is a potential immune reaction to a medical device that may not appear immediately but develops after repeated exposure. Unlike irritation, which is a local tissue reaction, sensitization is systemic. To ensure patient safety and obtain market approval, manufacturers must prove their devices do not leach chemicals that trigger allergic reactions.
At EBI, we perform sensitization testing in full compliance with ISO 10993-10, offering all three recognized methodologies to suit your specific device type and ethical considerations.
Which Test Method Should You Choose?
Selecting the right assay depends on your device’s material, its intended use, and the target regulatory market (e.g., MDR vs. FDA).
- LLNA (Local Lymph Node Assay): Recommended by ISO 10993-10 and the preferred „Gold Standard” for the EU market (MDR). As a 3Rs-aligned method using mice, it provides quantitative results and a shorter turnaround time. Note: May produce false positives with surfactants or certain metals.
- GPMT (Guinea Pig Maximization Test): Traditionally considered the „Gold Standard” for its extreme sensitivity. It uses an adjuvant to boost the immune response and is often required for novel materials or when LLNA is technically not feasible.
- Buehler Test: A non-adjuvant method using guinea pigs. It is typically reserved for topical devices (patches, creams) or materials where the aggressive GPMT might produce false positives.
Our Testing Methodologies
1. GPMT: Guinea Pig Maximization Test (Magnusson & Kligman)
The most sensitive assay for detecting weak allergens.
This test determines if the medical device extract can induce a systemic immune response. It involves an „Induction Phase” to prime the immune system and a „Challenge Phase” to observe reactions.
- Extraction: Samples are extracted in both polar (e.g., saline) and non-polar (e.g., vegetable oil) vehicles.
- Induction (Days 0-7): Intradermal injection with Freund’s Complete Adjuvant (FCA) followed by topical application to boost sensitivity.
- Challenge (Day 21): A topical patch of the test item is applied to a fresh site on the animal.
- Readout: Skin is scored for erythema (redness) and edema (swelling) at 24h and 48h after patch removal.
- Turnaround Time: ~12 weeks.
2. LLNA: Murine Local Lymph Node Assay
The modern, faster alternative focusing on the 3Rs (Reduction, Refinement, Replacement). Preferred method for the EU market (MDR).
Instead of looking for skin reactions, the LLNA measures the proliferation of lymphocytes in the lymph nodes draining the application site (the ears of mice). It is a quantitative assay.
- Process: The test item is applied topically to the ears of mice for 3 consecutive days.
- Analysis: After a 2-day rest, lymph nodes are harvested. We calculate the Stimulation Index (SI) by comparing cell proliferation in treated animals versus controls.
- Result Criteria:
- Non-sensitizing: SI ≤ 1.6
- Sensitizing: SI > 1.6
- Turnaround Time: ~8 weeks (Fastest option).
3. Buehler Test
Often selected for surface-contact devices and topical preparations due to its non-invasive nature. However, for the EU market (MDR), the LLNA remains the preferred and first-choice method as per ISO 10993-10.
This assay uses direct topical application without intradermal injection or adjuvants, simulating real-world usage for skin-contact devices.
- Induction Phase: Closed patches containing the test item are applied to the guinea pigs’ skin for 6 hours, once a week for 3 weeks.
- Challenge Phase: 14 days after the last induction, a challenge patch is applied to a new site.
- Readout: Sites are graded for allergic reactions (edema/erythema) at 24h and 48h.
- Turnaround Time: ~12 weeks.
Sample Requirements
Please refer to the table below to prepare your samples. Note that LLNA requires significantly less material than Guinea Pig methods.
| Test Method | Material Thickness | Surface Area Required | Weight / Volume | Minimum Quantity |
|---|---|---|---|---|
| GPMT (Guinea Pig) |
< 0.5 mm | 240 cm² | - | 6 items |
| ≥ 0.5 mm | 150 cm² | - | 6 items | |
| Powder / Solids | - | 8 grams | - | |
| LLNA (Mouse) |
< 0.5 mm | 50 cm² | - | 6 items |
| ≥ 0.5 mm | 25 cm² | - | 6 items | |
| Powder / Solids | - | 2 grams | - | |
| Buehler | - | 120 pieces of 2.5 cm × 2.5 cm | - | - |
Note: For the Buehler test, providing pre-cut patches is preferred to ensure consistent dosing.
Standards & Compliance
- ISO 10993-10: Biological evaluation of medical devices — Part 10: Tests for skin sensitization.
- ISO 10993-12: Sample preparation and reference materials.
- OECD Guidelines: (OECD 406 for GPMT/Buehler, OECD 429/442 for LLNA).
How We Work
Discovery & Insight
We begin with an in-depth consultation to understand your needs, challenges, and objectives. This helps us define the right strategy and scientific approach for your project.
Design & Development
Our experts translate your vision into actionable plans — combining innovative research, data, and technology to build precise and reliable solutions.
Delivery & Support
We implement the solution with full transparency and ongoing communication. After delivery, we stay involved — supporting you with optimization, updates, and future improvements.
FAQ: Sensitization Testing
Why does Sensitization take so long (8-12 weeks)?
Unlike cytotoxicity (which takes days), sensitization testing relies on the biological timeline of the immune system. We must allow time for the „induction phase” (the body recognizing the allergen) and a „rest period” before the „challenge phase” occurs. Attempting to rush this biology would result in invalid data.
Is Sensitization testing mandatory for all devices?
It is mandatory for almost all devices that have direct or indirect contact with the patient or user, regardless of contact duration (limited, prolonged, or permanent).
Can I use LLNA for any device?
LLNA is excellent for many chemicals and extracts, but it has limitations. It may not be suitable for devices containing certain metals (like nickel) or high concentrations of surfactants, which can trigger non-immune inflammation (false positives). Our toxicologists will review your composition to recommend the best path.
Why does Sensitization take so long (8-12 weeks)?
Unlike cytotoxicity (which takes days), sensitization testing relies on the biological timeline of the immune system. We must allow time for the „induction phase” (the body recognizing the allergen) and a „rest period” before the „challenge phase” occurs. Attempting to rush this biology would result in invalid data.
Is Sensitization testing mandatory for all devices?
It is mandatory for almost all devices that have direct or indirect contact with the patient or user, regardless of contact duration (limited, prolonged, or permanent).
Can I use LLNA for any device?
LLNA is excellent for many chemicals and extracts, but it has limitations. It may not be suitable for devices containing certain metals (like nickel) or high concentrations of surfactants, which can trigger non-immune inflammation (false positives). Our toxicologists will review your composition to recommend the best path.
Contact with us
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Location:
Europejski Instytut Biomedyczny sp. z o.o.
ul. Bartycka 63A lok. 6, 00-716 Warszawa
Mail:
contact@ebi.bio
Phone:
+48 22 780 06 32
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