Copper peptide-incorporated 3D-printed silk-based scaffolds promote vascularized bone regeneration

Bioactive ions are promising materials for vascularized bone regeneration. However, trace elements, e.g., copper, exert their effects in a narrow concentration range and cause cytotoxicity when over-accumulated, which limits their potential application in tissue engineering. In this regard, naturally occurring nanosized metallopeptides provide new insight into the novel usage of metal ions. Here, 3D-printed silk-based scaffolds with sustained release of copper peptide, a copper ion-specific binding tripeptide, were fabricated and exhibited similar therapeutic effects to free copper ions, with lower toxicity. We found that copper peptide promoted the polarization of M2 macrophages, which exhibited an anti-inflammatory phenotype and assisted in bone tissue repair during early stage. Moreover, the released copper peptide provided a microenvironment to stimulate transplanted bone marrow-derived stem cell (BMSC) proliferation and cytokine secretion. The secreted cytokines further promoted angiogenesis in vitro and in vivo. In addition, in vivo critical-sized calvarial defect regeneration experiments further demonstrated that fabricated scaffolds seeded with BMSC, resulting in better vascularized bone repair. Altogether, the results indicated that copper peptide incorporated silk-based scaffolds are promising materials for vascularized bone tissue regeneration, as well as providing new approaches for bioactive ion-based biomaterial design.