Regenerated Silk Fibers Obtained by Straining Flow Spinning for Guiding Axonal Elongation in Primary Cortical Neurons

Abstract

The recovery of injured nervous tissue, one of the main goals for regenerative therapeutic approaches, is often hindered by the limited axonal regeneration ability of the central nervous system (CNS). In this regard, the identification of scaffolds that support the reconstruction of functional neuronal tissues and guide the alignment of regenerating neurons is a major challenge in tissue engineering. Ideally, the usage of such scaffolds would promote and guide the axonal growth, a crucial phase for the restoration of neuronal connections and, consequently, the nerve function. Among the materials proposed as scaffolds for CNS regeneration, silk has been used to exploit its outstanding features as a biomaterial to promote axonal regeneration. In this study, we explore, for the first time, the possibility of using high-performance regenerated silk fibers obtained by straining flow spinning (SFS) to serve as scaffolds for inducing and guiding the axonal growth. It is shown that SFS fibers promote the spontaneous organization of dissociated cortical primary cells into highly interconnected cellular spheroid-like tissue formations. Neuronal projections (i.e., axons) from these cellular spheroids span hundreds of microns along the SFS fibers that act as guides and allow the connection of distant spheroids. In addition, it is also shown that SFS fibers serve as scaffolds for neuronal migration covering short and long distances. As a consequence, the usage of high-performance SFS fibers appears as a promising basis for the development of novel therapies, leading to directed axonal regeneration.

Silk Fibroin: An Ancient Material for Repairing the Injured Nervous System

“…In addition, SFS leads to the production of fibers without the usage of the aforementioned harsh solvents. Silk fibers produced by SFS have been assessed in vitro and have promoted the organization of cortical primary cells allowing for the structural re-connection of distant neural spheroids, favoring neural cell migration and axonal guidance [53]. .…”

“…Based on the biocompatibility of the SF biomaterials in vitro and in vivo and the properties of this material that drive neuronal migration and axonal guidance [53], it would be interesting to examine whether SF might have a significant application for axonal tracts growth and the functional rewiring of localized neurodegenerative damages.…”

“…Recently, we have identified that SF fibers obtained through SFS seem to have a natural compatibility for axonal guidance [53]. Application of SF surface modification can be further improved once an external stimulus such as electrical stimulation is also introduced.…”

Review on Fabrication and Application of Regenerated Bombyx mori Silk Fibroin Materials

“…Besides these conventional processes, straining fl ow spinning recently appears as a versatile and robust technique that allows effi cient spinning of regenerated silk fi bers. Geometrical and hydrodynamic processing parameters can be integrated into this technique, which allows spinning under a much wider range of chemistries [63]. Liquid exfoliation, which directly exfoliates silk nanofi brils from degummed silk fi bers, is another newly developed method that can preserve the native structural elements and features of silk fi bers with the aim to rearrange them at the nanofi bril level for enhanced properties [64,65].…”

Recent progresses in novel in vitro models of primary neurons: A biomaterial perspective

“…Uniaxial temperature gradient field crystallization of silk fibroin solution could produce silk scaffold with oriented channels, allowing neurons to align in oriented pores ( Zhang et al, 2012 ). Regenerated silk fibers produced by straining flow spinning, with diameter of only 2 μm, facilitated directional migration and axon elongation of neurons ( Mercado et al, 2020 ). However, the electrospun fibers either lack the interconnected pore, making the cells difficult to infiltrate and migrate, or present insufficient supporting strength.…”