Efficient
delivery of bone morphogenetic protein-2 (BMP-2) with
desirable bioactivity is still a great challenge in the field of bone
regeneration. In this study, a silk fibroin/chitosan scaffold incorporated
with BMP-2-loaded mesoporous hydroxyapatite nanoparticles (mHANPs)
was prepared (SCH-L). BMP-2 was preloaded onto mHANPs with a high
surface area before mixing with a silk fibroin/chitosan composite.
Bare (without BMP-2) silk fibroin/chitosan/mHANP (SCH) scaffolds and
SCH scaffolds with directly absorbed BMP-2 (SCH-D) were investigated
in parallel for comparison. In vitro release kinetics indicated that
BMP-2 released from the SCH-L scaffold showed a significantly lower
initial burst release, followed by a more sustained release over time
than the SCH-D scaffold. In vitro cell viability, osteogenic differentiation
of bone marrow mesenchymal stem cells (BMSCs), and the in vivo osteogenic
effect of scaffolds in a rat calvarial defect were evaluated. The
results showed that compared with bare SCH and SCH-D scaffolds, the
SCH-L scaffold significantly promoted the osteogenic differentiation
of BMSCs in vitro and induced more pronounced bone formation in vivo.
Further studies demonstrated that the mHANP-mediated satisfactory
conformational change and sustained release benefited the protection
of the released BMP-2 bioactivity, as confirmed by alkaline phosphatase
(ALP) activity and a mineralization deposition assay. More importantly,
the interaction of BMP-2/mHANPs enhanced the binding ability of BMP-2
to cellular receptors, thereby maintaining its biological activity
in osteogenic differentiation and osteoinductivity well, which contributed
to the markedly promoted in vitro and in vivo osteogenic efficacy
of the SCH-L scaffold. Taken together, these results provide strong
evidence that mHANPs represent an attractive carrier for binding BMP-2
to scaffolds. The SCH-L scaffold shows promising potential for bone
tissue regeneration applications.