Evaluation of new biomaterials The importance of cell culture studies in using the example of degradable osteosynthesis material of a magnesium alloy

The regulations for the approval of biomaterials are regulated by a national law called "Medizinproduktegesetz". Cell culture studies on the biocompatibility of biomaterials are of great importance and are characterized in ISO standards. In many cases, however, despite the efforts to reduce the use of animal experiments, preclinical material testing in animal models is obligatory before clinical studies can be carried out on the application of biomaterials. A new biomaterial for temporary implants are degradable magnesium alloys of varying compositions. The in vitro studies of the magnesium alloy show no limited biocompatibility when using eluates. Incubation of human cells in direct contact, however, there is a reduction in the number of metabolically active cells. Our investigations in the animal model present signs of a degradation of the implants while the outer shape is unchanged and the radiological measured volume is not reduced. The bone fracture healing is not adversely affected by the implants. The bone tissue adjacent to the magnesium alloy has lacunae and the bone-to-implant contact is lower in comparison to titanium implants. Whether this observation is an effect of the gas formation that displaces the bone tissue, or it is an indication of insufficient biocompatibility, remains unclear. An argument for sufficient biocompatibility of the material is, however, there is new bone formation and mineralized matrix directly on the surface of the magnesium implants, as well as in the margins of the lacunae. The example of the in vivo and in vitro study of the osteosynthesis plates demonstrates that both cell culture studies and animal experiments are indicated to investigate new biomaterials prior to application to the patient. The effects of biomaterials on complex biological processes such as wound healing, bone fracture healing and homeostasis of the bone makes necessary examinations in contact to the tissues in the living organism.