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Cytotoxicity Testing

About HTW Laboratory:

We offer professional cytotoxicity testing at a lower cost than other labs. Our customized testing solutions can enhance process efficiency and reduce testing cycles. For technical regulation support, technicians at HTW are able to help you understand technical regulations and product design specifications. Communicate with our experts to determine your needs and we will provide you with a free evaluation, proposal and quotation.


The cytotoxicity test is designed to evaluate the general toxicity of medical devices and materials. Testing involves extracting devices in a cell culture media and then exposing the extract fluid to mouse fibroblast cells (L929). The cells are allowed to grow in the extract fluid for a specified amount of time before the cells are evaluated using either qualitative or quantitative methods. The test is performed on all medical devices with patient contact, raw materials, and devices undergoing a cleaning validation or residual manufacturing.

Applicable Standards

  • ANSI/AAMI/ISO 10993-5

Email us if you have any questions or would like to consult an expert in our laboratory.

Study Outline for Cytotoxicity/MEM/Agar Overlay

MEM Elution
Devices/materials are generally extracted in serum-supplemented mammalian cell culture media (MEM) 37 ± 1ºC. After extraction, the extracts are placed in contact with a monolayer of L-929 cells (mouse fibroblasts). The cells are then allowed to grow in the extraction fluid for a specified amount of time before the cells are evaluated using either qualitative or quantitative methods.

  • qualitative

Qualitative evaluation involves observing the cells under a microscope and assigning a cytotoxic grade (0-4). The grade is based on an estimated percent lysis (death) and on the morphology (appearance) of the cells. Test materials pass the assay if the cytotoxic score is ≤ 2 (≤ 50% lysis).

  • Quantitative

Quantitative evaluation utilizes a tetrazolium dye which is used to assess the metabolic activity of cells. The results are reported as percent viability (% living cells). Test materials pass the assay if the percent viability if ≥ 70%. Multiple dilutions of the test article extract are generally included with each assay.

Agar Overlay

Materials are generally tested by surface area using at least 100 mm2 of material per well. Weight may also be used for liquids, gels, or powders using at least 100 mg per well. The material is placed on a layer of agarose that is placed on top of a monolayer of L-929 cells and incubated for 24 – 26 hours at 37 ± 1ºC in 5 ± 1% CO2. After incubation, the zone of cell destruction is measured and scored based on a 0 – 4 scale listed in AAMI/ANSI/ISO 10993-5. The material meets ISO requirements if the cytotoxic response is not greater than grade 2 (mildly reactive). Although Agar Overlay has been historically an accepted test method it may not be appropriate when submitting to certain regulatory bodies.

Cytotoxicity Failures

Occasionally, a device or material will exhibit a level of cytotoxic reactivity that is higher than what is allowed by the ANSI/AAMI/ISO 10993-5 standard and will result in a failed test. Although your product may have failed a cytotoxicity test, it does not necessarily mean that your device or material is unsafe for clinical use. It simply means that you are obliged to identify the source of failure and assess any toxicological risks.

Our Experts Can Help

There are several possible causes for cytotoxicity failure, and HTW Labs offers services to help you identify and assess the failure. From there, our experts can assess any potential toxicological risk to patient safety.

We evaluate the materials and processes associated with the device. Based on this information, our experts will often recommend targeted analytical chemistry to determine the cause of the failure. We can then work with clients to justify the failure through testing and assessment.

A discussion with our experts to identify the cause of cytotoxicity failure and develop an action plan often leads to manufacturers successfully submitting their device for regulatory approval without any further action.

Why Choose Us?

HTW Lab, accredited by CNAS, CMA, CNCA & A2LA, consistently operates competently and generates accurate and valid results in accordance with ISO/IEC 17025. Our lab meets the requirements of Good Laboratory Practice (GLP) and provides product testing service in accordance with national and global standards for both active and non-active medical devices. We are also IECEE CB Scheme Test Laboratory (CBTL). Thus, testing reports from HTW Lab can be accepted between countries.

Your Benefits at a Glance:

1.20 Years of experience

HTW has extensive experience in all types of devices and regulatory requirements across markets. 

2.Provide free modification service

Together with our wealth of knowledge in complex regulations globally, HTW provides a complete suite of testing solutions according to your needs including free modification service.

3.Save time to global markets

With over 7,000 square meters of labs, HTW offers the best testing cycles and you don't have to wait in line, HTW offers 1-on-1 service.With our in-depth insight of global product quality and regulatory requirements, HTW can optimize your costs and minimize your time to market.

4.Complete qualifications

ISO/IEC 17025 lab, accreditated by CNAS, CMA,A2LA,GLP.

5.Competitve price

Testing costs are lower than other labs.


You can also contact us directly by email.

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