Tailoring 3D hydrogel systems for neuronal encapsulation in living electrodes

State-of-the-art neurorprostheses rely on stiff metallic electrodes to communicate with neural tissues. It was envisioned that a soft, organic electrode coating embedded with functional neural cells will enhance electrode-tissue integration. To enable such a device, it is necessary to produce a cell scaffold with mechanical properties matched to native neural tissue. A degradable poly(vinyl alcohol) (PVA) hydrogel was tailored to have a range of compressive moduli through variation in macromer composition and initiator amount. A regression model was used to predict the amount of initiator required for hydrogel polymerization with nominal macromer content ranging between 5 and 20 wt%. Hydrogels at 5 and 10 wt% were reliably formed but 15 wt% and above were not able to be fabricated due to the light attenuation properties of the initiator ruthenium at increased concentration. Compressive modulus of hydrogels decreased upon incorporation of biomolecules (sericin and gelatin), however, the bulk stiffness spanned the range required to match neural tissue properties (0.04-20kPa). Neuroglia cells, such as Schwann cells survived and grew within the scaffold. The significant finding of this work is that the PVA-tyramine system can be tuned to provide a soft degradable scaffold for neural tissue regeneration while presenting bioactive molecules for cellular expansion. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 273-287