Biomimetic Silk Fibroin Scaffolds Functionalized with Hydroxyapatite and Platelet Growth Factors for Bone Tissue Engineering

Non-union fractures represent a significant clinical challenge requiring innovative therapeutic approaches. Silk fibroin (SF) scaffolds have gained recognition as advantageous biomaterials for bone tissue engineering due to their biocompatibility and mechanical characteristics. This study investigated the biocompatibility and osteoinductive potential of SF scaffolds functionalized with hydroxyapatite (HA) and loaded with platelet growth factors (PGFs) using hematopoietic stem cells (HSCs). SF scaffolds were prepared and functionalized with HA through methanol impregnation, while PGFs were obtained from platelet lysate via apheresis procedures. HSCs were cultured on different experimental groups, namely SF, SF-HA, PGF, SF-PGF, and SF-HA-PGF, assessing biocompatibility through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Live/Dead staining, and cytoskeleton analysis over 7 days. Osteoinductive properties were evaluated using Alizarin Red staining for mineral matrix deposition at 14 and 21 days. The MTT assay revealed the biocompatibility of all the experimental groups. The Live/Dead assay confirmed high cell viability, while the cytoskeleton analysis revealed well-organized actin filaments comparable to controls. Alizarin Red staining showed that PGF alone promoted early mineral matrix deposition at day 14, while SF-HA, SF-PGF, and SF-HA-PGF groups demonstrated significantly enhanced mineralization at day 21 compared with SF alone. The combination of silk fibroin scaffolds with platelet growth factors alone or with hydroxyapatite and platelet growth factors creates a biomimetic environment that supports cell viability and induces the osteogenic differentiation of hemopoietic stem cells. These findings suggest significant potential for clinical translation in treating non-union fractures and bone defects.