Development of carbon nanotubes-reinforced cell-derived matrix-silk fibroin scaffolds for bone tissue engineering

The bone tissue engineering approaches have been focused on mimicking bone tissue structure, composition, and hierarchy. With this in mind, the present work's main goal was to produce an improved scaffold that mimicked bone tissue structure, mechanical properties, and composition. For that, silk fibroin was mixed with decellularized cell-derived extracellular matrix and strengthened with carbon nanotubes. Then, enzymatic cross-linking, freeze modeling, and decellularization methods were combined to create carbon nanotubes-strengthened cell-derived matrix-silk fibroin scaffolds. The evaluation of carbon nanotubes-strengthened cell-derived matrix-silk fibroin scaffolds’ structure and mechanical properties showed that scaffolds were elastic, presented pore sizes of ≈ 112 ± 22 µm, a total porosity of ≈ 75 ± 3%, and stiffness of ≈ 5 kPa. After, their in vitro bioactivity was investigated, showing the formation of mineral deposits.

The biological evaluation in vitro revealed that scaffolds supported the adhesion, spreading, the proliferation of human adipose-derived stem cells (hASCs). Ultimately, developed carbon nanotubes-strengthened cell-derived matrix-silk fibroin scaffolds promoted the differentiation of hASCs along the osteoblastic lineage without the need for an osteogenic supplemented medium. This positive influence was confirmed by collagen secretion, increased ALP activity, and expression of osteogenic-related genes (e.g., ALP, Runx-2, Col Iα, and OPN). Furthermore, carbon nanotubes-reinforced cell-derived matrix-silk fibroin scaffolds were hemocompatible and enabled the infiltration of cells.

Overall, these favorable results confirmed that the developed carbon nanotubes-strengthened cell-derived matrix-silk fibroin scaffolds hold an excellent promise for bone tissue engineering scaffolding applications.