Controllable growth of spiral ganglion neurons by magnetic colloidal nanochains

Nerve regeneration based on neural stem cell therapy has become a promising cure for neurological disorders in recent decades. Various kinds of biomaterials have been developed to guide the oriented growth of newborn neurites, which is the fundamental factor to the synaptic connection of newly differentiated neurons with the desired partners during the regeneration. However, the applied biomaterials are usually incapable of guidance with multiple directions, besides, the underlying guiding mechanism has yet to be clearly stated. In this paper, a novel guiding approach based on the magnetic colloidal nanochains was designed for the oriented growth of newborn neurites. The magnetic colloidal nanochains with aligned topography were fabricated from the self-assembly of the magnetic colloidal nanoparticles under the magnetic field. Well orientation of the newborn neurites from the seeded spiral ganglion neurons (SGNs) was found along the nanochains, which induced the alignment of the seeded SGNs. In addition, the growth cone development and synapse formation of the seeded SGNs was promoted under the guidance of the nanochains, which possessed important significance in the rearrangement of nerve network and recovery of neural signal communication during the regeneration. Importantly, the multidirectional nanochains could be constructed by regulating the magnetic field, which contributed to the oriented guidance of SGNs alignment with multiple directions. This feature facilitated to the complex regenerate environment of the nervous system in vitro. Furthermore, the underlying guiding mechanism was revealed by the transcriptome analysis, which showed well consistent with the "contact guidance" of the nanochains. Thus, it was demonstrated that the magnetic colloidal nanochains possessed huge value in biomedical applications.