Horseradish Peroxidase-Crosslinked Calcium-Containing Silk Fibroin Hydrogels as Artificial Matrices for Bone Cancer Research

Hydrogels, being capable of mimicking the extracellular matrix composition of tissues, are greatly used as artificial matrices in tissue engineering applications. In this study, the generation of horseradish peroxidase (HRP)-crosslinked silk fibroin (SF) hydrogels, using calcium peroxide as oxidizer is reported. The proposed fast forming calcium-containing SF hydrogels spontaneously undergo SF conformational changes from random coil to β-sheet during time, exhibiting ionic, and pH stimuli responsiveness. In vitro response shows calcium-containing SF hydrogels’ encapsulation properties and their ability to promote SaOs-2 tumor cells death after 10 days of culturing, upon complete β-sheet conformation transition. Calcium-containing SF hydrogels’ angiogenic potential investigated in an in ovo chick chorioallantoic membrane (CAM) assay, show a high number of converging blood vessels as compared to the negative control, although no endothelial cells infiltration is observed. The in vivo response evaluated in subcutaneous implantation in CD1 and nude NCD1 mice shows that calcium-containing SF hydrogels are stable up to 6 weeks after implantation. However, an increased number of dead cells are also present in the surrounding tissue. The results suggest the potential of calcium-containing SF hydrogels to be used as novel in situ therapeutics for bone cancer treatment applications, particularly to osteosarcoma.