Freeze-Casted Keratin Matrix as an Organic Binder to Integrate Hydroxyapatite and BMP2 for Enhanced Cranial Bone Regeneration

An ideal bone regenerative scaffold is expected to possess architectural characteristics that mimic the bone tissue, osteoconductive properties, and osteoinductive functionality. Key challenges to creating a scaffold with these ideal characteristics simultaneously are the selection of appropriate processing methods and biocompatible materials. Herein, human hair keratin is proposed as an organic binder for the simultaneous incorporation of bone's major inorganic component, hydroxyapatite and bone's growth factor, recombinant human bone morphogenetic protein 2 (rhBMP2) to enable both osteoconductive and osteoinductive characteristics in the creation of bone scaffolds. Furthermore, a freeze-casting method is selected to fabricate this rhBMP2-incorporated keratin/hydroxyapatite (KHA) scaffold with aligned lamellar pores to guide and promote bone regeneration. The aligned KHA scaffolds display better mechanical properties, sustained rhBMP2 release, good cell compliance, and 3D cellular infiltration. Implantation of KHA scaffolds in vivo reveals that scaffolds with aligned pores effectively accelerate the healing process of bone defects compared to scaffolds with random pores. This work indicates the distinctive potential of freeze-casted rhBMP-2 incorporated KHA scaffolds for bone regeneration.