(462e) Hydrogel Composite Materials for Long-Term Neurotrophin Delivery In Neural Prostheses

Long-term implanted electrode arrays have a significant importance in neural prosthetics for recording the electrical signals from nearby neurons and generating electrical signals to stimulate nearby tissue. Therefore, the density of neurons and their proximity to the electrode sites play an important role in the electrode performance. In the past decades, biodegradable and biocompatible polymers have been used as electrode coatings to minimize the acute and chronic inflammatory response and to preserve neurons near the recording sites. Since poly(ethylene glycol) (PEG) is nontoxic, non-immunogenic, and inert to most biological molecules, such as proteins, block copolymers of PEG have been studied in our group to form hydrogels as the scaffolds that can support or stimulate neuron growth. The results of our previous work demonstrated that the hydrogels could be used as a short-term (1~3 weeks) controlled delivery system for neurotrophins (the growth factors which can stimulate the neurite extensions) in vitro. To further reduce the acute immune response (usually lasts for 6~8 weeks) caused by the insertion of electrodes and to enhance integration of neurons with electronic circuitry, we have constructed composite drug delivery systems comprised of polymeric hydrogels (i.e., poly(ethylene glycol)-poly(lactic acid), (PEGPLA) or poly(ethylene glycol)-polycaprolactone, (PEGPCL)), and other vehicles, such as biodegradable poly(lactic co-glycol acid) (PLGA) microspheres or polycaprolactone (PCL)-based electrospun nanofibrous scaffolds, to provide neurotrophins at a predetermined rate for 2~3 months in vivo. The stable and sustained release of neurotrophins can remarkably enhance the attraction, attachment and restoration of neurons around the chronically implanted electrodes.