All-hydrogel biocompatible and multifunctional fiber neural probe

Abstract

The development of a neuronal tissue compliant neural probe is necessary to achieve chronic implantation with minimal signal loss. Although fiber-based neural probes fabricated by the thermal drawing process have been proposed as a solution, there is still mechanical and biochemical mismatch between polymer based fiber neural probes and brain tissue. Here, we proposed a multifunctional, biocompat- ible and soft hydrogel neural probe with functional components of electrode, optical waveguide, and passive drug delivery. The hydrogel electrode, made with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and reduced graphene oxide, and hydrogel waveguide was examined to have adequate functionalities for the electrophysiological recording of extracellular potential and for the optogenetic stimulation. On the other hand, the soft hydrogel sham probe was found to elicit less foreign body response than other sham probes made with rigid materials (steel, silica, and polycarbonate). Furthermore, the hydrogel neural probe was observed to have capability of delivering the hydrophilic anti-inflammatory drug, dexamethasone 21-phosphate disodium salt, expected to more alleviate the foreign body response. This research proposed a new type of implantable neural probe, all which is made with the polyurethane hydrogel, and it is expected to elongated the lifetime of neural interface with minimal immune response. We believe our hydrogel fiber probe will be extensively utilized for chronic neuroscientific researches and cllinical applications for the extended periods of years or decades.