Bioactive Self-Assembling Peptide Hydrogels Functionalized with Brain-Derived Neurotrophic Factor and Nerve Growth Factor Mimicking Peptides Synergistically Promote Peripheral Nerve Regeneration

Various artificial materials have been fabricated as alternatives to autologous nerve grafts in peripheral nerve regeneration, and these afford positive recovery effects without the disadvantages of the gold standard. In this study, we prepared a three-dimensional functionalized self-assembling peptide nanofiber hydrogel containing two neurotrophic peptides (CTDIKGKCTGACDGKQC and RGIDKRHWNSQ derived from nerve growth factor and brain-derived neurotrophic factor, respectively) that reflected the structure and properties of the neural extracellular matrix. The material was used to promote axonal regrowth and functional recovery. Scanning electron microscopy revealed a three-dimensional porous matrix within the hydrogel. Circular dichroism spectroscopy and atomic force microscopy confirmed that the peptides displayed a β-sheet structure and self-assembled into long nanofibers. Rheology measurements and atomic force microscopy indicated that the elasticity of the peptide hydrogels was close to that of the nerve tissue matrix. In vitro work with Schwann cells and dorsal root ganglia showed that the hydrogels exhibited good cell compatibility. Furthermore, the hydrogel containing CTDIKGKCTGACDGKQC and RGIDKRHWNSQ promoted the neurite outgrowth of PC12 cells significantly compared to non-functionalized peptide. In vivo, the hydrogels were placed into chitosan tubes and used to bridge 10 mm long sciatic nerve defects in rats. We found that the combination of CTDIKGKCTGACDGKQC and RGIDKRHWNSQ accelerated axonal regeneration and afforded good functional recovery, suggesting that they synergistically facilitate peripheral nerve regeneration.