Lysozyme aggregates functionalization of carbon nanotubes for biomimetic hydroxyapatite mineralization

Natural bones, typical organic-inorganic hybrid composite, are comprised of hydroxyapatite (HAp) crystals and collagen nanofibrils, and bionic composites play a key role in the development of bone substitute. However, carbon nanotubes (CNTs), which possess great potential for collagen substitute, are still a challenge for use in bone graft due to its cytotoxicity. Furthermore, biomineralization of bone-like HAp crystals with hierarchical structure and excellent mechanical strength induced by CNTs remains challenging. Herein, inspired by the hierarchical structure of natural bone, CNTs/HAp hybrid composites are successfully mediated by lysozyme aggregates through biomineralization. Abundant functional groups on the lysozyme aggregates-coated CNTs enrich the interface with bonded calcium and phosphate ions, facilitating the nucleation and growth of HAp crystals with c-axis orientation being similar to bone-like crystals. Owing to the adhesion originated from biofilm, lysozyme aggregates could readily integrate HAp on CNTs surface with excellent bonding stability under external pulling force, supporting attachment and proliferation of cells and bone tissues. Therefore, this biocompatible and biomimetic composites with osteoconductivity holds potential application on bone repair surgery and synthetic bone graft substitutes.