Materials considerations of implantable neuroengineering devices for clinical use

Implantable devices for recording and stimulation of the human nervous system offer promise for the treatment of disorders including spinal cord injury, stroke, traumatic brain injury, sensory and motor deficits, chronic pain, epilepsy, Parkinson’s disease and amputation. While advances in neuroengineering devices have been impressive, often the expectations and desires for a chronically implantable device remain unrealized. In the face of engineering approaches which perform well on the bench or in acute implantations is an immune response which is well-tuned to recognize foreign bodies, including the materials chosen for our innovations. Recent years have demonstrated a co-evolution of engineering solutions for neural disorders and knowledge of underlying biological hurdles. This review describes the state-of-the-art for implantable neuroengineering devices used for electrical recording and stimulation, the tissue response to these devices, and emerging technologies and materials to mitigate the tissue response. The test methods for candidate materials and paths to the commercial market are briefly described.