Structurally and functionally optimized silk fibroin-alginate-based biomimetic scaffolds reinforced with nanobioceramics for bone tissue engineering applications

In this study, we prepared chemically crosslinked silk fibroin (SF) and sodium alginate (Alg) biomimetic scaffolds reinforced with bioceramic nanohydroxyapatite (nHAp) for bone tissue engineering (BTE) applications. The pore sizes of these scaffolds were effectively controlled by varying the composition of the SF/nHAp/Alg biocomposites. The scaffold prepared with a 40:20:40 SF: nHAp: Alg ratio exhibited excellent swelling properties, reaching over 1700% within 70 min. In vitro degradation studies demonstrated that these biomimetic scaffolds exhibited controlled degradation, taking over 30 days to achieve 50% degradation. The scaffolds also showed good mechanical properties; they maintained structural integrity and did not break, even under a load approximately 800 times their own weight. Additionally, scaffolds loaded with synthetic peptide salmon calcitonin effectively controlled initial burst release and enabled sustained therapeutics delivery for up to two weeks. The biocompatibility of the scaffolds was evaluated using in vitro cell viability and hemolysis assays, which revealed good safety for human dermal fibroblast cells and negligible toxicity to rabbit red blood cells. Importantly, the scaffolds promoted cell proliferation and alkaline phosphatase secretion in human bone marrow stem cells. Histological and immunological analyses in a scaffold-implanted mouse model have demonstrated biocompatibility, supporting osteoclastic resorption and osteoblastic mineralization by downregulating RANKL. Furthermore, the chick chorioallantoic membrane assay showed the excellent angiogenic properties of the scaffold. These results suggest that the bioceramic-reinforced SF/Alg biomimetic scaffold has significant potential for use in BTE.