Silk as a Multifunctional Biomaterial Substrate for Reduced Glial Scarring around Brain-Penetrating Electrodes

The reliability of chronic, brain-penetrating electrodes must be improved for these -neural recording technologies to be viable in widespread clinical applications. One approach to improving electrode reliability is to reduce the foreign body response at the probe-tissue interface. In this work, silk fibroin is investigated as a candidate material for fabricating mechanically dynamic neural probes with enhanced biocompatibility compared to traditional electrode materials. Silk coatings are applied to flexible cortical electrodes to produce devices that transition from stiff to flexible upon hydration. Theoretical modeling and in vitro testing show that the silk coatings impart mechanical properties sufficient for the electrodes to penetrate brain tissue. Further, it is demonstrated that silk coatings may reduce some markers of gliosis in an in vitro model and that silk can encapsulate and release the gliosis-modifying enzyme chondroitinase ABC. This work establishes a basis for future in vivo studies of silk-based brain-penetrating electrodes, as well as the use of silk materials for other applications in the central nervous system where gliosis must be controlled.