Multi-scale, multi-level anisotropic silk fibroin/metformin scaffolds for repair of peripheral nerve injury

Silk fibroin (SF) as a natural polymer has a long history of application in various regenerative medicine fields, but there are still many shortcomings in silk fibroin for using as nerve scaffolds, which limit its clinical application in peripheral nerve regeneration (PNR). In this work, a multi-scale and multi-level metformin (MF)-loaded silk fibroin scaffold with anisotropic micro-nano composite topology was prepared by micromolding electrospinning for accelerating PNR. The scaffolds were characterized for morphology, wettability, mechanical properties, degradability, and drug release, and Schwann cells (SCs) and dorsal root ganglia (DRG) were cultured on the scaffolds to assess their effects on neural cell behavior. Finally, the gene expression differences of neural cells cultured on scaffolds were analyzed by gene sequencing and RT-qPCR to explore the possible signaling pathways and mechanisms. The results showed that the scaffolds had excellent mechanical properties and hydrophilicity, slow degradation rate and drug release rate, which were enough to support the repair of peripheral nerve injury for a long time. In Vitro cell experiments showed that the scaffolds could significantly promote the orientation of SCs and axons extension of DRG. Gene sequencing and RT-qPCR revealed that the scaffolds could up-regulate the expression of genes related to SCs proliferation, adhesion, migration, and myelination. In summary, the scaffolds hold great potential for promoting PNR at the micro/nano multiscale and physical/chemical levels and show promising application for the treatment of peripheral nerve injury in the future.