Marine-Inspired Three-Dimensional Printed Biosilica-Spongin Scaffolds as Promoters of Osteogenic Differentiation and...

Marine sponges provide bioactive components of interest for bone tissue engineering, particularly biosilica (BS) and spongin (SPG). BS resembles the mineral phase of bone, while SPG, a collagen-like protein, contributes elasticity and biocompatibility. Their combination allows the fabrication of bioinspired scaffolds capable of guiding osteogenesis. In this work, 3D-printed alginate scaffolds were produced with increasing BS content (50-70% w/w) or with BS combined with SPG (35-49% BS, 15-21% SPG). Rheological tests confirmed predominantly elastic behavior in all bioinks, with G' higher than G″ across the linear viscoelastic range. SEM revealed BS spicules evenly distributed within alginate and alginate-SPG matrices, generating integrated fibrous networks. Compression assays showed progressive reinforcement with higher BS content: BS3 (70% BS) reached 6.64 ± 1.19 MPa, while BS-SPG3 (49% BS + 21% SPG) presented the best overall performance (E = 2596.16 ± 257.23 Pa; σ_u = 12.44 ± 3.77 MPa). Si release increased over 14 days, peaking at 13.87 mg/L for BS3 and 26.43 mg/L for BS-SPG3. Cell assays with MC3T3-E1 confirmed biocompatibility. Migration was favored in BS-rich scaffolds, especially BS3, while BS-SPG remained comparable to the control. ARS staining highlighted stronger mineral deposition in BS3 and BS-SPG3 at days 7 and 14. Gene expression of RUNX-2, OCN, and BSP was upregulated, most markedly in BS3 and BS-SPG3, confirming their osteoinductive character. Together, these results demonstrate that BS-SPG scaffolds combine structural reinforcement, controlled ion release, and biological activity, supporting their potential as sustainable candidates for bone regeneration.