Considerations on surface and structural biocompatibility as prerequisite for long-term stability of neural prostheses

Neural prostheses are technical systems that partially substitute neural functions of the body after traumatic lesions or neurological disorders. Using biomedical microsystems, complex implants can be designed and fabricated in very small dimensions. However, miniaturization of neural prostheses for long-term implantation is very challenging. Implants not only have to be biosafe and biostable in terms of cytotoxicity and degradation, they also have to cope with the biological requirements of structural biocompatibility. In this paper, examples of biomedical microimplants for neural prostheses use are introduced. Results from basic biocompatibility investigations regarding the cytotoxicity are reported, as well as aspects of the interaction between surface structure and cell behaviour. A detailed outlook addresses possible approaches to use nanosciences to ensure long-term stability of thin technical layers within the body and create surfaces for selective and specified functional reactions at the interface between the artificial implant and the biological environment.