Three-dimensional carbon nanotube frameworks favor spinal cord explant rewiring of motor outputs.

Neural interfaces are at the core of prosthetic devices, such as implantable stimulating electrodes or brain machine interfaces, and are increasingly designed for assisting rehabilitation and for promoting neural plasticity. Thus, beyond the classical neuro-prosthetic concept of stimulating and/or recording devices, modern technology is pursuing towards ideal bio/electrode interfaces with improved adaptability to the brain tissue. Advances in materials research are crucial in these efforts and new developments are drawing from engineering and neural interface technologies. We exploit here a micro-porous, self-standing, three-dimensional (3D) interface made by polydimethylsiloxane (PDMS) implemented at the interfacing surfaces with novel conductive nano-topographies (carbon nanotubes) with which cells can actively interact. We characterize the porosity of the elastomeric scaffolds by threedimensional X-ray micro-tomography reconstructions. We use these structures to interface axons regenerated from cultured spinal cord explants and we show that engineering PDMS 3D interfaces with carbon nanotubes effectively changes the efficacy of regenerating fibers to target and re-connect segregated explant pairs. We

The regrowth of severed axons is fundamental to reestablish motor control after spinal-cord injury (SCI). Ongoing efforts to promote axonal regeneration after SCI have involved multiple strategies that have been only partially successful. Our study introduces an artificial carbon-nanotube based scaffold that, once implanted in SCI rats, improves motor function recovery. Confocal microscopy analysis plus fiber tracking by magnetic resonance imaging and neurotracer labeling of long-distance corticospinal axons suggest that recovery might be partly attributable to successful crossing of the lesion site by regenerating fibers. Since manipulating SCI microenvironment properties, such as mechanical and electrical ones, may promote biological responses, we propose this artificial scaffold as a prototype to exploit the physics governing spinal regenerative plasticity.

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