Bacterial nanocellulose enhances osteogenic activity of Vat-based 3D-bioprinted silk fibroin hydrogels

Tissue engineering, particularly leveraging three-dimensional (3D) bioprinting, is emerging as a transformative solution to repair critical-size bone defects. However, identifying suitable biomaterials remains a key technological bottleneck in the field. Toward this broader goal, this study explored a composite bioink containing photocurable silk fibroin (SF) and bacterial nanocellulose (BNC) for fabricating scaffolds for bone tissue engineering (BTE) by 3D bioprinting using digital light projection (DLP). We prepared scaffolds with 0, 0.25, and 0.75 wt% BNC and characterized their physicochemical properties (degradation, viscoelasticity, porosity, compressive strength). We assessed samples in simulated body fluid (SBF) after 14 days to evaluate biomineralization. Additionally, using MC3T3-E1 preosteoblast cells, we examined cell viability, metabolic activity, proliferation, and osteogenic potential through alkaline phosphatase (ALP), Alizarin Red S (ARS), von Kossa, hematoxylin and eosin (H&E), and Picrosirius Red assays. The optimized bioinks produced hydrogels with controlled degradation, tunable viscoelasticity, interconnected pores, and significantly improved compressive strength. Specifically, 10 % methacrylated-silk with 0.75 % BNC (Silk-MA/0.75BNC) showed superior mechanical properties compared to 10 % Silk-MA or 10 % Silk-MA with 0.25 % BNC (Silk-MA/0.25BNC). In vitro studies confirmed enhanced biomineralization with Silk-MA/0.75BNC, increased calcium deposits, and improved cell viability and metabolic activity with BNC incorporation. Hence, the 3D-bioprinted composite scaffolds were shown to effectively support cell proliferation, with the 0.75 % BNC bioink significantly stimulating osteogenic markers. These results underscore the potential of Silk-MA/BNC composite bioinks for advanced 3D bioprinting of BTE constructs.