Cytotoxicity test

The EN ISO 10993 series of standards covers various aspects of the biological evaluation of medical devices and helps to demonstrate their safety. Both, novel and established tests can be found in the more than 20 parts of the series. One of the best known and widely used tests is probably EN ISO 10993-5:2009.

DIN EN ISO 10993-5:2009
Biological evaluation of medical devices – Part 5: Tests for in vitro cytotoxicity

Nobody wants to come into contact with toxic or harmful products, all the more so if it is a medical device. In case a product has the property to damage or destroy cells, this is called cytotoxicity. However, manufacturers do not always have enough detailed information from the supply chain to be able to assess the compatibility of the materials – this is where the cytotoxicity test described in the EN ISO 10993-5 standard comes into play. This is a comparatively inexpensive test that enjoys great popularity and is frequently used – also because cytotoxicity according to EN ISO 10993-1 is an endpoint to be evaluated for almost all products. So it makes sense to carry out the test for cytotoxicity during the development phase to identify suitable materials, and later also on the finished device (if applicable sterile, in packaging) and in combination with EN ISO 10993-18, the chemical characterisation, in order to be able to interpret the results clearly and make a reliable statement.
Contamination can also be detected quickly, e.g. in the context of quality assurance, and “clean” goods with the corresponding properties can thus be identified quite inexpensively.

The 5th part of the 10993 series of standards thus describes test methods for assessing the in vitro cytotoxicity of medical devices.

These procedures specify the cultivation of cells, either in direct contact with a medical device and/or extracts of a medical device, or also by diffusion.
The methods are suitable for determining the biological response of mammalian cells in vitro using appropriate biological parameters.

A test scheme is intended to help in the selection of the appropriate test procedure. The test procedures are roughly divided into

  • Extract testing
  • Testing with direct cell/material contact, as well as
  • Test with indirect cell/material contact.

Depending on the type of sample, application and possible application sites, one or more of the mentioned test methods are selected. There are a variety of possible tests and endpoints, and depending on the type of measurement, different evaluation criteria may apply:

  • Estimates of cell damage due to morphological changes
  • Cell damage measurements – evaluation depending on the materials used
  • Cell growth measurements
  • Measurements of specific aspects of cell metabolism.

The material properties in particular can have an influence on the exact test planning and implementation. In the case of spandex, for example, a different test protocol is used that takes the specific properties into account.

Our partner Hohenstein Medical reports on this from the test laboratory:

Dear Sir or Madam,
we would like to have our medical device tested for cytotoxicity according to DIN EN ISO 10993-5, please send us an offer.

Many of the enquiries we receive at Hohenstein Medical by e-mail are similar to this. The cytotoxicity test is one of our standard tests and the quotation is quickly prepared. The offer is followed by the order and we get the sample sent to us.
An extract is then prepared from the test samples in the laboratory, which is incubated with living cells. Following an incubation period of 72 hours, protein staining is used to determine the growth inhibition compared to a control.
If the test turns out suspiciously in the end, the question of why often arises.
Unfortunately, the test itself does not provide any answers to this, as only the effectiveness on the cells used is examined. It is not an analysis of individual substances. Often, as a laboratory, we do not have any more detailed information on the product to be tested.
However, detailed information on the product and its composition is essential for the biological evaluation according to the EN ISO 10993 series of standards and the selection of suitable/necessary tests.
For example, we can offer a different version of the cytotoxicity test for products containing elastane. Elastane is known to be frequently cytotoxic, so a specially adapted version of EN ISO 10993-5 for compression hosiery and similar products was published in 2018 by C. Wiegand et al. Here, the initial cell count is chosen somewhat higher and acidic sweat solution is used as the extraction agent, as sweat on intact skin is the most relevant liquid. After incubation on the cells for 24 h, the growth inhibition is determined on the one hand by means of protein staining and on the other hand the LDH activity in the cell culture supernatant compared to a control.
If no or only little information about the product is available or can be obtained, it makes sense to first have a chemical characterisation carried out according to EN ISO 10993-18. Based on this data, it is then easier to determine the best method for the respective product. In this way, the question: “Why did my product fail?” can possibly be avoided in advance.

With this insight, we want to show you that Hohenstein Medical tests according to standardised methods, but always in light of the actual product properties. Do you still have difficulties in defining these properties and creating a biological evaluation plan? seleon GmbH will be happy to support you in creating your documentation.

Further information on biological assessment and expected contaminants

Have you done everything correct from your point of view? Defined and communicated product properties, created a biological evaluation plan according to EN ISO 10993-1, carried out chemical characterisation according to EN ISO 10993-18 and still got unexpected values in the cytotoxicity test? Then take a look at the new: 

We also give you an insight into this standard on our blog: Cleanliness of medical devices

Please note that all details and listings do not claim to be complete, are without guarantee and are for information purposes only.