Preparation of chitosan rods with excellent mechanical properties: One candidate for bone fracture internal fixation

Chitosan (CS) is one promising material as a temporary mechanical supporter for bone fracture internal fixation. In our previous work, we successfully fabricated CS rods through one in situ precipitation route. But bending strength and bending modulus of CS rods need to be improved to match the commercially available devices used for bone fracture internal fixation. In this research, CS rods were reinforced effectively through cross-linking reaction by using glutaraldehyde as the coupling reagent. Schiff's base was detected by FTIR due to the chemical reaction between amino groups and aldehyde groups. Crystal plane space of CS rods became small during the formation of network structure. Microstructure was observed by SEM, indicating that layer-by-layer structure became much tighter after cross-linking reaction, and cracks in one layer turned around when they reached another layer to absorb energy. Bending strength and bending modulus of cross-linked CS rods could reach 186.3 MPa and 5.17 GPa, respectively. Compared with uncross-linked CS rods, they are increased by 101.6% and 26.1%, respectively. As a result, mechanical properties of CS rods are equivalent to the commercially available biodegradable devices. CS rods with excellent mechanical properties are a good candidate for bone fracture internal fixation.