| Abstract: | Neural regeneration is a great clinical challenge in both the central nervous system (CNS) and the peripheral nervous system (PNS). Degeneration in the CNS caused by disease (such as Alzheimer’s or Parkinson’s diseases) or trauma (such as traumatic brain injury and spinal cord injury) often results in permanent paralysis and loss of sensation. The spontaneous neural regeneration in the CNS is generally unsuccessful, while the PNS has an intrinsic regenerative ability. However, PNS regeneration occurs over relatively short distances. Damage to the PNS results in the motor and cognitive impairment in many cases. Biomaterials in the form of scaffolds or nanoparticles for neuroprotection and neuroregeneration have attracted much attention. Nanoparticles can be fabricated using various lipids, polymers, metals, and carbon materials to carry drugs or growth factors. Here, biomaterial scaffolds for neural regeneration are highlighted. Some certain criteria for biomaterial scaffolds in neural regeneration should be met, for example, the biocompatibility for integration with the host tissues, the degradation rates close to the nerve growth, and the mechanical properties similar to the nerve tissue (Hsieh et al., 2015). A number of natural and synthetic polymers have been applied in neural regeneration, including collagen, gelatin, chitosan, alginate, hyaluronan, silk fibroin, poly(L-lactic acid), poly(glycolic acid), polycaprolactone, polyphosphoester, and polyurethane. To improve the bioactivity, conductive biomaterials such as polypyrrole, polythiophene, and polyaniline may enhance neurite outgrowth because electrical signals are transmitted for neuronal communication (Guo and Ma, 2018). Mechanical properties of biomaterial scaffolds can influence neural regeneration, where the soft materials (0.1–1 kPa) promote the neuronal differentiation but the stiffer materials (7–10 kPa) promote the glial differentiation (Tseng et al., 2015). Hydrogel and nerve guide conduit (NGC) are the most frequent choices of scaffolds in CNS and PNS regeneration [Figure 1]A. Moreover, self-healing injectable hydrogel and three-dimensional (3D) printed NGC with unique properties are attractive candidates in each category. |
