Experimental study of graphene oxide/hydrogel composite promoting intervertebral disc regeneration

Graphene oxide (GO) promotes cell adhesion and chondrogenic differentiation, while thermosensitive hydrogels enable injectable and in situ gelling for minimally invasive repair. This study prepared a GO/thermosensitive block copolymer (PEP) composite hydrogel and evaluated its effects on nucleus pulposus cell (NPC) behavior and intervertebral disc regeneration. GO was synthesized by a modified Hummers method and PEP by atom transfer radical polymerization. GO/PEP hydrogels with varying GO concentrations (0-1.0 mg/mL) were formulated. NPCs isolated from rat coccygeal discs were treated with GO/PEP extracts; cell proliferation was assessed by CCK_8 and viability by Calcein_AM/PI staining. In vivo, a mouse tail puncture_induced intervertebral disc degeneration (IDD) model was established. Mice were randomized into sham, PBS_treated IDD, and GO/PEP_treated IDD groups (n = 8/group). At 4 and 8 weeks post_injection, disc tissues were harvested for histology and NPC counting. GO/PEP extracts dose_dependently reduced NPC mortality (significant at GO ≥0.1 mg/mL, p < 0.05) and increased NPC proliferation (significant at GO ≥0.2 mg/mL, p < 0.01). In the IDD model at 4 weeks, NPC count in the IDD + PBS group (103 ± 15.34) was significantly lower than in the sham group (675 ± 12.75, p < 0.001). The GO/PEP group showed increased NPC count at 4 weeks (337 ± 21.47, p < 0.01 vs sham) and further recovery at 8 weeks (665 ± 14.58, not significantly different from sham, p > 0.05). Histological analysis revealed restored annulus fibrosus integrity, even NPC distribution, reduced central cavity, and enhanced proteoglycan recovery. In conclusion, the GO/PEP thermosensitive hydrogel exhibits excellent biocompatibility and injectability, inhibits NPC apoptosis, promotes proliferation, and restores degenerated disc structure, offering a promising cell_free, minimally invasive strategy for IDD treatment.