Bioinspired arrangement of nanohydroxyapatite in chitin matrix for high-strength bone plates.

Biological materials composed of inorganic nanofillers and biopolymeric matrix (e.g., bone and crab shells) generally display excellent mechanical performance. However, conventional chitin/nanohydroxyapatite composites exhibit limited mechanical properties, primarily due to the random distribution and aggregation of nanohydroxyapatites within the chitin matrix. Herein, we develop uniaxially and biaxially oriented chitin/nanohydroxyapatite hydrogels through a facile stretching strategy. The influences of pre-stretching/transversely strains and nanohydroxyapatite morphology (spherical, rod-shaped, and sheet-like nanohydroxyapatites) on the structure and mechanical properties of hydrogels were systematically investigated. Finally, the bone plates were prepared through sequential solvent exchange, drying, and machining of biaxially oriented hydrogels containing sheet-like nanohydroxyapatites. The resultant plates showed high tensile strength (102 MPa) and toughness (7.9 MJ/m3) and exhibited good biocompatibility and biodegradability. This work presents a straightforward strategy for fabricating high-performance plates by controllably arranging nanohydroxyapatites within a chitin matrix.