Nanofiber reinforced alginate hydrogel for leak-proof delivery and higher stress loading in nucleus pulposus.

Injectable hydrogels effectively remodel degenerative nucleus pulposus (NP) with a resemblance to the in vivo microenvironment. However, the pressure within the intervertebral disc requires load-bearing implants. The hydrogel must undergo a rapid phase transition upon injection to avoid leakage. In this study, an injectable sodium alginate hydrogel was reinforced with silk fibroin nanofibers with core-shell structures. The nanofiber-embedded hydrogel provided support to adjacent tissues and facilitated cell proliferation. Platelet-rich plasma (PRP) was incorporated into the core-shell nanofibers for sustained release and enhanced NP regeneration. The composite hydrogel exhibited excellent compressive strength and enabled leak-proof delivery of PRP. In rat intervertebral disc degeneration models, radiography and MRI signal intensities were significantly reduced after 8 weeks of injections with the nanofiber-reinforced hydrogel. The biomimetic fiber gel-like structure was constructed in situ, providing mechanical support for NP repair, promoting the reconstruction of the tissue microenvironment, and finally realizing the regeneration of NP.