Biomatieral Screening: Making Biocompatibility Measurable.

A telemetric microsensor implant continuously evaluates the ingrowth behavior of biomaterials in animal models.

The aim is to develop a hybrid biomaterial for tracheal implants made of porous titanium scaffolds filled with bioactive hydrogel to control cell migration. To ensure mechanical stabilization at the implant site, the surrounding tissue must connect to the implant through cell ingrowth. In the continuous evaluation of this ingrowth behavior, previous methods from histology have reached their limits. At the NMI, oxygen, pH and electrical impedance sensors are integrated on an intelligent microimplant, which continuously records the ingrowth behavior of the hybrid biomaterial based on physical/chemical properties.


DIN EN ISO 10993 Part 6 describes special test procedures for the analysis of local tissue reactions to implantable biomaterials. To date, however, there is no legal regulation specifying obligatory boundary conditions for biomaterial animal tests. Rather, these boundary conditions depend on the size, surface area, chemical composition of the biomaterial, application or implantation site, which in most cases cannot be standardized by law. For endpoint analysis at the end of the test phase, all test animals have to be sacrificed. Macroscopic and histological studies at the tissue/implant interface are compared with selected reference materials and documented in a report.

However, the development of new biomaterials tends towards increasingly dynamic bioactive in vivo properties. Changes in material properties (e.g. degradation rate, bioactivity) as well as transients in the tissue over time are to be expected. These continuously varying biological/chemical processes can so far only be captured by animals sacrificed at discrete time points by premature explantation. This creates the following conflict: the shorter the interval between these time points, the more animals are needed.

In the NMI subproject, we aim to monitor, quantify and classify the ingrowth behavior of hydrogel materials and titanium sponges in soft tissue by measuring the physical/chemical properties of the biomaterial/tissue interface in soft tissue of New Zealand White Rabbits. Based on this application example, at the end, the developed new in vivo biomaterial test will be available for other biomaterial types. The establishment of this new biomaterial testing method requires the development of a medium- to long-term stable wirelessly controllable microsensor implant. For this purpose, microelectrodes are realized using thin-film technology. A telemetry unit (Smart Implant Project) will be hermetically encapsulated together with the microimplant.

The BiMoT (Biomaterial Implant Monitoring Test) is the first system available to biomaterial developers and testers that can detect transients during the ingrowth phase of biomaterials without the need for animal sacrifice. This allows the parallel validation of a high number of chemical variations of the same material at a low cost per test while respecting ethical constraints to reduce animal testing. In addition, the recorded parameters are still quantifiable and thus enable a clearly comprehensible delimitation of different ingrowth behaviors, which will facilitate the approval of innovative implant materials with constantly increasing requirements in the field of tissue engineering and regenerative medicine.

01.12.2012 - 30.11.2015