Basics - Biocompatibility of medical devices

What does biocompatibility mean?

The definition provides the following information: "Ability of a medical device or material to perform with an appropriate host response in a specific application [ISO 10993-1]". That sounds too complicated? That's how we see it.

For example, a host reaction could be skin irritation. In general terms, they are undesired reactions / side effects.

Biocompatibility thus describes the ability of a medical device or material to function according to its intended purpose, while causing undesirable reactions of the human body only to the extent permitted.

A biocompatible material is well tolerated by the human body.

How is this related to medical devices?

Medical devices are often touched directly or indirectly by users or patients. This should not lead to unreasonable side effects caused by a material that is not well tolerated. To ensure this, materials and medical devices are tested for biocompatibility.

• Direct contact:
• The user touches the product during use
• The patient is touched by the product during application - a patch sticks to the patient's skin
• Indirect contact:
• The patient is injected with a liquid. The liquid was previously in a syringe. Since the liquid was in the syringe, the patient comes into indirect contact with the inside of the syringe

How can biocompatibility be proven?

Proof can be provided, for example, by biological tests and by assessing the effects of leachable chemicals. In addition, other material properties such as bound chemicals and the ability to maintain mechanical integrity can be tested - provided that this can have an impact on the biological reaction of the body in contact with the product.

Such tests are carried out by special laboratories and in some cases animal testing is used. In order to reduce the number of animal tests, attempts are often made to prove the biocompatibility of materials on the basis of existing data. The extent to which this is possible must be examined in each individual case. In addition, ISO 10993-1 describes that in-vitro tests should be preferred to in-vivo tests if they are sufficiently reliable. There is therefore also an indication at the level of this standard that unnecessary animal testing should not be carried out.

What are the difficulties with this?

Often the materials of medical devices are not the problem at all. Residues that remain on the product due to manufacturing, sterilization or other sources can also be critical. These materials must be identified and, if necessary, removed if they are not biocompatible.

In addition, there are many different ways in which the human body can react to an incompatible material. Some of these occur very quickly, others are delayed. Skin irritation will be noticed quickly. An adverse effect on the reproductive ability or hormone balance, on the other hand, is more difficult and will be noticed later.

In order to cover all aspects of biocompatibility, there are a number of different standards from the ISO 10993 series. Depending on the product and its intended purpose, it must be checked which of these standards are applicable.

Must all medical devices be biocompatible?

ISO 10993-1 contains a diagram with various questions to help you complete the biological assessment and thus the determination of biocompatibility. The first question aims to determine whether there is direct or indirect patient contact. If the answer is negative, ISO 10993-1 is not applicable.

However, the MDR requires that products should be designed in such a way that the safety of the user is also guaranteed. This also includes aspects of biocompatibility, as users often have direct contact with a medical device when using it.