Clear guidance for ISO-compliant cytotoxicity testing

Cytotoxicity testing is one of the most commonly used methods for evaluating the biological safety of medical devices. However, delays in regulatory approval, confusion over the right testing approach, and repeated reworks due to failed cytotoxicity assays are the kinds of setbacks that stall timelines, inflate budgets, and limit progress. Uncertainty around sample sizes, extraction methods, and the right assay for your material or indication often compounds the challenge.

Eurofins Medical Device Services network of laboratories offers deep technical expertise, end-to-end project support, and cutting-edge assay platforms to help you avoid these issues and move forward with confidence. With 30+ years of experience in biological safety testing and a track record of ISO 10993-5 and USP <87> compliance, we provide fast, flexible cytotoxicity testing tailored to your device and submission strategy. We also interpret results and identify sources of test failures, provide toxicological risk assessments for failed assays, and deliver clear reporting that supports submission-ready documentation.

As both a critical screening tool and a key biological endpoint for regulatory submissions, cytotoxicity assesses a material’s potential to inhibit cell growth or cause cell death. These in vitro assays, performed using either qualitative or quantitative methods, provide a rapid yet sensitive analysis of the biological reactivity of leachables or diffusible substances. Eurofins Medical Device Services network of laboratories applies validated cell culture techniques - shown to correlate well with animal assays - to support the safe development of medical devices used in or on the human body. The appropriate test method is selected based on the sample’s nature, intended site, and conditions of use. We’ll work with you to select the right test system based on the device’s density, extractability, and intended use.

 

Characterization Test System
Cell Contact with Extract / Solution of the test item Growth inhibition / viability Qualitative Elution Test
Quantitative

XTT

MTT

BCA
Colony forming ability Quantitative Colony Forming Assay
Direct Cell Contact Growth Inhibition – reactivity zones Qualitative Direct Cell Contact Assay
Indirect Cell Contact Growth Inhibition – decoloration and lysis indices Qualitative Agar Diffusion Test

Partner with our experts.

Regulatory and methods

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Qualitative evaluation methods

  • Agarose overlay
  • Agar diffusion test
  • Colony formation assay
  • Direct cell contact test
  • MEM elution assay
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Quantitative evaluation methods

  • BCA assay
  • MTT staining
  • Neutral Red Uptake (NRU) staining
  • XTT staining
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Regulatory

  • "Biological evaluation of medical devices Part 5: Tests for in vitro cytotoxicity" provides the general requirements for evaluating the cytotoxic potential of a medical device.
  • ISO 10993-1 Table A.1 – "Endpoints to be addressed in a biological risk assessment”

Which test system is best for my product?

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Agar diffusion test

The Agar Diffusion Test is an option if the test item cannot be extracted or dissolved in cell culture medium. It is also relevant that the test item does diffuse through, but does not react with the agar layer. The sponsor has to provide a justification for the test method in order to submit his test material with this test method (ISO 10993-5, ISO 7405).

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BCA

BCA can be used for submissions in Central Europe, while XTT and MTT both can be used for submissions worldwide. All three methods are performed with extracts or solutions of the test material (ISO 10993-5). The XTT assay is preferred over the MTT assay as it produces a water soluble formazan, thus not requiring a solubilization step before measuring.

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Colony forming assay

The Colony Forming Assay is specifically required by the authorities in Japan (ISO 10993-5, MHLW-guideline).

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Direct cell contact test

The Direct Cell Contact Test is designed for test materials with a flat surface that are neither low nor high-density materials. The test item is applied directly to the test system (ISO 10993-5).

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Elution test

The Elution Test is designed for the evaluation of extracts of elastomeric plastics or polymeric materials. It is appropriate for high-density materials (USP <87>). This test system can be combined with ISO for dose-response evaluations and quantitative assessment of cytotoxicity (ISO 10993-5).