An injectable high-conductive bimaterial scaffold for neural stimulation.

Neurological recovery is difficult due to limited axonal regeneration and the limitations of autograft therapeutics in repairing peripheral nerve defects. Alternatively, the implantable nerve guidance conduit represents a promising approach for the nerve regeneration of especially large injury gaps. Herein, we presented an easily injectable and highly conductive, tissue engineering scaffold for supporting nerve cells growth and promoting neural differentiation. The ultra-flexible conductive scaffold was prepared by the combination of PCL-based micro-grid via melt electrowriting (MEW) with a nanolayer of gold via sputter coating, which shows good mechanical properties (including high flexibility and recoverability) and high conductivity. The conductive interface acts as a bridge for electrical signal transmission between nerve cells under electrical stimulation, which significantly enhances neural differentiation and improves the neurite outgrowth. Specifically, compared with the PCL group, the neurite length of the 50 Au-PCL and 80 Au-PCL groups increased by nearly 10 and 15 times respectively, after 10 days of culture without ES treatment. Furthermore, as the increase of Au coating thickness, the promotion of the ES effect was further improved. The 80 Au-PCL group showed the highest average neurite length and neurite number per cell compared with PCL (11 times), 20 Au-PCL (9 times), 50Au-PCL (3 times) after ES treatment for 5 days (one hour per day). Overall, our Au-PCL bimaterial scaffold is a promising nerve repair material because of its suitable injectability, high conductivity, biocompatibility, and powerful ability to promote neural stimulation.