Extracellular matrix-based intracortical microelectrodes: Toward a microfabricated neural interface based on natural materials

Extracellular matrix (ECM)-based implantable neural electrodes (NEs) were achieved using a microfabrication strategy on natural-substrate-based organic materials. The ECM-based design minimized the introduction of non-natural products into the brain. Further, it rendered the implants sufficiently rigid for penetration into the target brain region and allowed them subsequently to soften to match the elastic modulus of brain tissue upon exposure to physiological conditions, thereby reducing inflammatory strain fields in the tissue. Preliminary studies suggested that ECM-NEs produce a reduced inflammatory response compared with inorganic rigid and flexible approaches. In vivo intracortical recordings from the rat motor cortex illustrate one mode of use for these ECM-NEs. Researchers have combined biocompatible collagen fibers with a gelatinous protein mixture for improved brain–prosthetic interfaces. Mark Allen from the University of Pennsylvania and co-workers from the Georgia Institute of Technology set out to solve the problems typically associated with clinical brain applications—such as a mismatch between the rigidness of the implant and brain tissue, which leads to strain and inflammation. The researchers developed new electrodes that are embedded in a collagen/gelatinous mixture and have sufficient rigidity to enter target brain tissue. After incorporation into the brain, the electrodes soften and produce desireable biomechanical characteristics under physiological conditions. In vivo experiments demonstrated that this strategy yields reduced long-term inflammatory responses than existing methods, representingone step toward the development of implantable devices with improved functionality and reduced strain on patients.