Fig. 1. Schematic illustration of the preparation of injectable hydrogel and the application in photothermal therapy of bone tumor and bone regeneration.

Fig. 2. SEM images and photographs of (a) Gel, (b) Gel/CPs. (c-f) Rheological analyses of hydrogel with CPs concentrations of 0-2 mg mL-1. (g, h) SEM images of CPs without/with soaked in SBF (scale bar of inset: 300 nm). (i) FTIR spectra and (j) XRD spectra of CPs without/with soaked in SBF. (k) XRD spectra of Gel/CPs soaked in SBF for 0, 10, and 28 days.

Fig. 3. Photothermal effects of hydrogel (a) with different concentrations of CPs at 0.37 W cm-2 and (b) different laser power densities at 1 mg mL-1. (c) Infrared thermal images of Gel/CPs with laser irradiation. (d) Photothermal effects of Gel/CPs with four heating-cooling cycles with laser irradiation of 0.52 W cm-2. (e) Photothermal response of CPs in aqueous solution with laser irradiation of 0.52 W cm-2 and then the laser is turned off to cool naturally at 840 s. (f) Time versus - lnθ obtained from the cooling period of Fig. 3(e).

Fig. 4. Cell cytotoxicity assay and photothermal effects on ablating tumor cells of hydrogel. (a) Cell cytotoxicity assay of human osteoblast cells co-cultured with hydrogel for 24, 48, and 72 h. Photothermal effects of hydrogel with (b) different irradiation durations and (c) different irradiation times after NIR laser irradiation of 0.52 W cm-2. (d) Fluorescence microscopic images of tumor cells co-cultured with hydrogel after irradiated for 0, 10, 20, and 30 min (green: live cells; red: dead cells). (e) SEM images of tumor cells co-cultured with hydrogel after irradiated for 0 and 20 min. Flow cytometry of tumor cells co-cultured with hydrogel after irradiated for 10 min: (f) Gel, (g) Gel + NIR, (h) Gel/CPs, (i) Gel/CPs + NIR. Error bars represent standard deviation from the mean (n = 4). Asterisks indicate statistically significant differences (*p < 0.05, **p < 0.01, ***p < 0.001).

Fig. 5. Photothermal effects on anti-tumor efficiency of injectable hydrogel in vivo. (a) Infrared thermal images, (b) photothermal curves of tumor-bearing mice with laser irradiation of 0.52 W cm-2 for 10 min. (c) Relative tumor volume and (d) body weight of tumor-bearing mice over the treatment time. (e) Tumor inhibition rates after treatment at 10 days. (f) Representative photographs of tumor-bearing mice after 0, 5, and 10 days. Photographs of tumor tissues at 10 days are shown in the bottom row. (g) H&E and TUNEL staining images of tumor tissues at 10 days (scale bar: 100 μm in H&E staining images, 50 μm in TUNEL staining images). Error bars represent standard deviation from the mean (n = 3). Asterisks indicate statistically significant differences (*p < 0.05, **p < 0.01, ***p < 0.001).

Fig. 6. Bone regeneration assessment in vivo. (a) Representative CT reconstructed images at 0, 4, and 8 weeks. (b) Representative images of CT slices in calvarial-defect site at 0 and 8 weeks. (c) Photographs of dissected calvaria at 8 weeks. (d) BV/TV ratios at 4 and 8 weeks. (e) Histological analysis at 8 weeks (scale bar: 500 μm zoomed in 40 × and 200 μm zoomed in 100 ×; yellow H: host bone; green N: new bone). Error bars represent standard deviation from the mean (n = 4). Asterisks indicate statistically significant differences (*p < 0.05, **p < 0.01, ***p < 0.001).