Additional file 1: Figure S1. Top-view, front-view and side-view pictures of Gel-SA, Gel-SA-4CuO, and Gel-SA-6CuO hydrogel scaffolds. Figure S2. Digital photographs of Gel-SA scaffold, Gel-SA-1CuO scaffold, Gel-SA-2CuO scaffold, Gel-SA-3CuO scaffold, Gel-SA-4CuO scaffold, Gel-SA-5CuO scaffold, and Gel-SA-6CuO scaffold under dry conditions from left to right. Figure S3. High-resolution XPS spectra of Cu 2p for CuO nanoparticles. Figure S4. Representative photographs of swelling behavior of Gel-SA-4CuO hydrogel scaffold. Figure S5. The side view of Gel-SA and Gel-SA-6CuO hydrogel scaffolds after incubation with water for indicated time. Figure S6. Representative photos of Gel-SA and Gel-SA-6CuO hydrogel scaffolds after degradation for 24 h. Figure S7. Time-dependent release of Cu2+ from Gel-SA-CuO scaffolds. Figure S8. Changes of body weight of mice with different treatments. Figure S9. The representative H&E staining images of major organs from tumor-bearing mice with different treatments.