Animal Surgical Procedure.

Following our established animal protocol, nucleus pulposus (NP) implant surgery was performed using aseptic technique and a surgical microscope.³⁵ General anesthesia was induced with intraperitoneal injection of ketamine/xylazine (60–80/5–10 mg/kg). Animals (male) were randomly divided into three groups: NP implant + saline, NP implant + amino-f-Gd₃N@C₈₀, and NP implant + amino-f-Sc₃N@C₈₀ groups (n = 6/group). In brief, the left L4/5 interlaminar space was exposed, followed by dissection of the coccygeal disc tissue (mainly NP with partial inner annulus fibrosus) from the same animal. Immediately after dissection from mouse tail and prior to implantation, coccygeal disc tissues were bathed in saline (0.9% NaCl), 1 μM amino-f-Gd₃N@C₈₀, and amino-f-Sc₃N@C₈₀ for 30 s, respectively, and then implanted over the exposed interlaminar space. Both amino-f-Gd₃N@C₈₀ and amino-f-Sc₃N@C₈₀ were diluted in saline (0.9% NaCl) for this experiment.