Medical devices have become indispensable to everyday life and represent a growing market. The application of medical devices ranges from huge machines (e.g. heart-lung machines) to diagnostic tools such as software and implants, injection needles and mechanical contraceptives, to mention only a few. The compatibility of the materials utilized to create medical devices with the biological surfaces they encounter is of high importance, especially for the use of such devices at and within the human body. This is the chance for nanotechnology to offer new possibilities and solutions by e.g. altering the surfaces of such devices to increase their compatibility.
What are medical devices and how are they defined?
Medical devices are strictly different from drugs or pharmaceutical products as medical devices, by definition, do not have a pharmacological or immunological effect and are not allowed to change their activity inside the body by adapted alterations (i.e. metabolism).
Medical devices are clearly regulated by law and an ordinance [1,2].
Medical devices may be very small or very big (from simple nanoparticles to joint implants or heart-lung machines). Regardless of their size, their compatibility must be guaranteed over their whole lifecycle.
Examples such as joint implants or heart valves illustrate clearly that such devices stay for long periods within the body and are in direct contact with the surrounding tissue. Thus, compatibility and safety of the materials which the medical devices are made from plays an important role.
For safety evaluations the medical devices are grouped into two different categories:
- Non-invasive applications, e.g. products which contact the skin from the outside such as stethoscopes or mechanical contraceptives
- Invasive applications (through surgery or not) such as: materials for wound healing, implantable devices, dental- or bone cement, injectable materials
Nanotechnology in medical devices
Nanotechnology is an indispensable part of the medical device field. The incredibly small size of batteries (e.g. for pacemakers) or electronic circuits and sensors utilized in medical devices today was made possible with nanotechnology. New ceramics for teeth filling or screws for dental implants consist more and more of materials derived from sintered nanopowders (comparable to 3D-printing) or have a specially designed surface made from so-called nanostructures.
Aside from the more obvious large devices there exists very small ones. Nanoparticles made from iron oxide are an approved medical device for the physical treatment of tumours (e.g. brain glioma), which are injected directly into the tumour tissue and, after stimulation by an external alternating magnetic field, will kill the tumour cells through overheating (hyperthermia) .
The above-mentioned iron oxide nanoparticles are only one example for the manifold applications of nanomaterials in the medical area. Bone substitutes and dental prosthetics are manufactured with ceramics or polymeric particles and reinforced with nanometre scale carbon fibres. Nanosilver is used within implants or on surfaces of catheters to reduce the possibility of inflammation after surgery. Many additional applications are within the testing phase. However, not all applications for nanotechnology are based on nanoparticles or nanomaterials.
Nanotechnology is also the basis for nanostructuring of surfaces which support the ingrowth of implants or are needed to improve adherence in the body . Whether it is a screw in a bone or a dental implant in the jaw or a complete hip joint, no inflammatory events should be caused after the surgery and the artificial part should be tolerated life-long without loss of function. The surfaces of pacemakers or other devices should not be recognized as a foreign material by the body’s immune system so that rejection reactions do not occur. Thus, coatings or various nanostructures are under investigation for such surfaces in order to enhance their compatibility and the durability within the body.
Legal basis for the safety of medical devices
The legally binding fundamentals for all medical devices are prescribed within the law about medical devices  and the related ordinance . In addition to the above described definitions, medical devices are categorized according to their residence time in the body. Distinct categories are presented for short (less than a day), medium (between one and 30 days) and permanent residence time (longer than 30 days); with detailed definitions and additional information provided by the “Scientific Committee on Emerging and Newly Identified Health Risks” (SCENIHR) . This committee provides clear instructions about what properties must be analysed and how the properties must be analysed to ensure all medical devices, even those which contain nanomaterials, are safe. In this regard, the testing of biological effects and toxicological responses are very important. Recently, various suggestions have been published regarding how and what should be measured [6-8]. As an example, as the result of mechanical abrasion, particles can be released e.g. by a joint implant. Therefore, one of the top priorities for such medical devices, whether they initially contain nanomaterials or not, is to prevent the release of small particles into the surrounding tissue. This abrasion phenomenon should be tested for all devices and potential health hazards presented by any resulting particles should be avoided.
Creation of medical devices encompasses a wide and innovative field with many opportunities for the development and use of new materials. Here nanomaterials play an important role for the enhancement of function and compatibility of many medical devices. As a result of their application on and in the human body, the demands on safety for such devices are very high.
- EU 2017/745 (MDR): Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices
- EU 2017/746 (IVDR): Regulation (EU) 2017/746 of the European Parliament and of the Council of 5 April 2017 on in vitro diagnostic medical devices
- Maier-Hauff, K et al. (2011), J Neurooncol, 103(2): 317-324.
- Bruinink, A et al. (2014), J.Biomed.Mater.Res.A, 102(1): 275-294.
- SCENIHR (2015). Report:”Guidance on the Determination of Potential Health Effects of Nanomaterials used in Medical Devices”, European Commission DG Health and Food Safety, Luxembourg
- Gubala, V et al. (2018), Pure Appl. Chem., 90(8): 1283-1324
- Gubala, V et al. (2018), Pure Appl. Chem., 90(8): 1325-1356
- Kerecman Myers, D et al. (2017), ALTEX, 34(4): 479-500