Integrating Eggshell-derived CaCO3/MgO Nanocomposites and Chitosan into a Biomimetic Scaffold for Bone Regeneration

Abstract The bone defects caused by trauma, tumor resections and congenital diseases can lead to deformity and dysfunction. Developing a biodegradable scaffold with tunable osteogenesis and degradation rates is highly essential for improving bone defect regeneration. Eggshell is a kind of natural biomaterial of which the major inorganic component is CaCO3. Herein, we synthesized MgO nanoparticle-coated eggshell particles (defined as CaCO3/MgO nanocomposites) and subsequently fabricated a biomimetic active scaffold through the chemical crosslinking of the CaCO3/MgO nanocomposite, carboxymethyl chitosan (CMC) and bone morphogenetic protein 2 (BMP2). The results showed that the modulus and compressive strength of the new composite CaCO3/MgO/CMC/BMP2 scaffold were higher than those of the CMC scaffold. Interestingly, the composite scaffold exhibited significant mineralization ability and strong osteogenic differentiation potential. Moreover, an examination of the osteogenic differentiation mechanism clearly illustrated that Mg2+ ions and BMP2 released from the composite scaffold could activate the phosphorylation of the ERK1/2 and Akt pathways and promote osteogenesis through the crosstalk of multiple pathways. Finally, an in-situ rat calvarial defect repair experiment showed excellent repair results of the composite scaffold. This study is very promising, as it provides new insights for developing natural CaCO3-based inorganic nanomaterials for tissue engineering and regenerative medicine.