Motion is a big part of our daily life: on average, we walk about 6,000 steps per day. We know that increased physical activity leads to better health and fitness, but sometimes extensive forces acting on our bodies can lead to injuries, which may be difficult to heal and hinder normal activities. Cartilage covers the surface of joints, acting as a shock absorber and allowing bones to slide over one another. When this linkage gets damaged, the regenerative process is very difficult and often requires advanced stem-cell therapies and biocompatible scaffolds.

In their communication in Advanced Materials, Professor Yingfang Ao from Peking University Third Hospital, Haifeng Chen from Peking University, and colleagues prepare a structurally and functionally optimized 3D-printed, silk-fibroin–gelatin scaffold for in vitro and in vivo cartilage repair. 3D printing was used to generate scaffolds with a uniform pore size of 350 µm to maximize cell proliferation.

Gelatin, as a partial derivative of collagen, allows for good biocompatibility and enhanced cell adhesion. On its own, however, it does not have the necessary mechanical strength to endure large stress. To overcome this, the authors introduced silk fibroin into the structural matrix. By controlling the β-sheet content through ethanol treatment, the mechanical properties and degradation rates could be significantly improved.

In vitro studies revealed that compared with SFG scaffolds, peptide-conjugated scaffolds SFG–E7 had a higher recruitment capacity for BMSCs, as assessed by measuring the effluent amount of cells after 12 and 24 hours of culturing. SFG–E7 scaffolds also had higher chondrogenic capacity than SFG scaffolds, as evidenced by more hydroxyprolin and glycosaminoglycan production, and collagen type II expression in vitro.

The in vivo results indicated that the SFG group had a better repair effect than a microfracture (MF) control group. Furthermore, neo-cartilage in the SFG–E7 group was more similar to normal cartilage than the SFG group through a series of assessments, including gross observation, magnetic resonance imaging, histology, scanning electron microscopy, and biomechanics evaluation.

To find out more, please visit the Advanced Materials homepage.