Systematic assessment of the biocompatibility of materials for inkjet-printed ozone sensors for medical therapy

The biocompatibility of medical sensors is of great importance. In order to prevent harm of the patient during measurement, this aspect must be considered throughout the entire design process. Biocompatibility can be achieved by various methods. For example, the sensor can be encapsulated, only biocompatible materials can be used for the sensor, or anti-inflammatory agents can be applied to the surface of the sensor. In this paper the focus is on sensors fully fabricated from biocompatible materials. Two exemplary inkjet-printed amperometric and impedimetric sensors are systematically assessed regarding their biocompatibility. Both sensors can be used for the measurement of dissolved ozone during oxygen-ozone injection therapy. For the sensors each material is evaluated with respect to the international standard ISO 10993. Overall, many amperometric and impedimetric sensors are fabricated from a small set of materials. The assessment reveals that for this specific application an amperometric sensor consisting of gold and silver nanoparticle inks, inkjet-printed on a polydimethylsiloxane membrane, and passivated with SU-8 ink offers the highest biocompatibility and reaches a good compliance with other important requirements. In addition, biological characterization tests are required for the specific medical application to validate the biocompatibility. From this study, it can be concluded that the findings on biocompatibility can also be transferred to other sensors that are made of the same set of materials but are for other applications. This applies to oxygen, glucose, pH, hydrogen peroxide, sweat lactate, and acetone sensors.