Design of Sr-doped hydroxyapatite nanoparticles loaded on chitosan scaffold for promoting the spinal cord injury repair

[Display omitted] •The Sr-HAP ceramics with uniform morphology has been synthesized via a facile precipitation strategy.•The as-prepared Sr-HAP with has been incorporated into the chitosan polymer scaffold to carry drugs for SCI repair.•The CS/Sr-HAP nanocomposite delivery system achieves improved in vitro drug release behavior and scarce cell toxicity.•The CS/Sr-HAP composite carrier is able to form more synaptic connections among new neurons to promote SCI repair. Axon degeneration and neurons after spinal cord injury (SCI) can lead to the serious sensory and motor dysfunctions. The effective treatment of SCI still remains a grand clinical challenge for current medicine. Development of biological scaffolds with drugs are of great significance to provide a supportive environment for re-establishment of cellular connections and growth of new tissues after SCI. In this study, we presented the synthesis of strontium-doped hydroxyapatite (Sr-HAP) with high biocompatibility and osteoconductivity, which was a promising biomaterial for repair of hard/soft tissues. The Sr-HAP nanoparticles was obtained by a classical precipitation process followed by the loading on macroporous chitosan (CS) scaffold. The CS/Sr-HAP nanocomposite was characterized with SEM, XRD, and FT-IR techniques, which was used to carry drugs for guiding nerve regeneration. We have performed the in vivo experiment by transplanting the scaffolds carried with chymopapain into an acute rat with SCI model. The robust neurogenesis of neural stem cells (NSCs) was observed, which then transformed into the functional neurons and the injured gap can be reconnected. This study suggests that the CS/Sr-HAP nanocomposite scaffold has great potential for promoting the spinal cord repair.