Biocompatibility testing questions

What is biocompatibility testing for medical devices?

According to the MDR and FDA regulations biocompatibility must be demonstrated for all medical devices. If a device is biocompatible if performs its function without adverse effects on adjacent tissue or the organism. Biocompatibility testing follows a review of component materials and a biological safety risk analysis. This process is described in ISO 10993. In the standard the safety requirement is defined according body contact and duration. Chemical characterisation can be used to define the majority of these requirements.


How does ISO 18562 relate to ISO 10993?

ISO 18562 describes specific biocompatibility requirements for air paths in breathing components. Many components will have only transitory contact with skin and therefore do not need testing, but do need to be included in an ISO 10993 Biological Evaluation Report. The requirements for test are: particulate release, vapour (VOC) release and leachate (usually in condensed water) transmission to the patient. The ISO 18563-4 leachate test includes analytical chemistry, sensitization and cytotoxicity from ISO 10993. The chemical characterisation combined with toxicological assessment can replace the sensitization test.


Is biological testing still required for medical devices?

The 2018 version of ISO 10993 emphasises risk assessment and chemical understanding. This means that if the combination of chemicals and materials in a device are known and their toxicity is known, this information can be combined to with knowledge of the product's use to eliminate biological testing when appropriate. It is still a good idea to conduct cytotoxicity testing and in some cases an investigation of local effects.

Is chemical extract testing required for medical devices?

ISO 10993 has chemical characterisation as the first requirement in the testing matrix. It encourages the use of this chemical analysis when insufficient information is available to define all the required toxicity end points. It is only required if the material review and risk assessment conclude that this information is not  available.

What are biocompatibility end points?

There are many ways in which a material can be toxic. In medical device regulations these are described as end points. A substance could damage DNA and be mutagenic or carcinogenic; it could cause inflammation after the immune system has been primed and be sensitizing; it might irritate the tissues which it contacts. These end points must be considered in the risk analysis for a medical device. The relationship between end points and body contact is defined in the ISO 10993 matrix. In conjunction with this standard the risk analysis could conclude that: sufficient information is available and no testing is required; or that chemical analysis of leachables is required; and /or that biological testing is required

How do I calculate sample requirements for medical device biocompatibility testing?

Part 12 of ISO 10993 details the ratio of extract solvent volume to device surface required to produce the test fluids. This ratio can be applied to devices and pharmaceutical containers. Your testing supplier will be able to advise you on what volume of fluid is required for each test. In the case materials characterisation, and leachables and extractables the required volume is often 50 to 100ml.

What is the testing biocompatibility matrix?

The biological evaluation matrix in ISO 10993 lists end points for toxicity assessment for medical devices. The end points required are defined according to the invasiveness of the device's use and its duration of contact. An end point is a toxicological risk that must be discussed and evaluated with the object of showing that the risk from a device is insignificant when compared to the benefit. Examples are cytotoxicty, geneotoxicity and mutagenicity.

What is chemical characterisation?

Chemical characterisation is a combination of information obtained by reviewing information sources including:

  • the input materials (specification, MSDS, safety testing)
  • processing (heating, contact with other materials, other stresses)
  • the storage conditions,
  • sources of contamination,
  • the effects of sterilisation,
  • any information obtained from chemical testing.

 This is the information that a Toxicologist can use to weigh up the risks of using the device. This Toxicological Risk Analysis can conclude whether or not the device is safe to use or if biological testing is required to confirm some aspect of safety. Hence, biological testing is the ‘gold standard’ but also the ‘last resort’.

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