mechanism, combined with the design of bone-like structure, and constructed a bone defect repair scaffold with hierarchical order structure bone-like structure from the perspectives of component and structure.
Firstly, high-strength chitosan-nanocellulose composite materials were prepared as the structural framework of the whole scaffold using the alkali-urea solvent system. The resultant composites were physically crosslinked, avoiding the introduction of biological toxicity or damaging the excellent properties of natural polymers. The behaviour of nanocellulose in alkali-urea solvent system was explored; the preparation process of chitosan-nanocellulose composite hydrogel via alkali-urea solvent system was optimized; the influence of the introduction of nanocellulose on the gel strength and structure was studied.
Secondly, the natural polymer chitosan with good biocompatibility was used to form the ordered arrangement of the central canal of the Harvard system in the cortical bone through the self-organization process. This process shares homology with the formation mechanism of biological tissue, which was difficult to achieve by conventional pore-forming methods. The occurrence conditions of bone-like porous channel and the influence of the introduction of nanocellulose were explored. The microstructure and mechanical properties of chitosan-nanocellulose composite hydrogel prepared via acid solvent system were studied, and the mechanism was analyzed by comparing with the composite hydrogel prepared via alkaline solvent system.
Ulteriorly, inorganics were loaded in the complex ordered structure formed by self-organization. Nano-hydroxyapatite was introduced into the ordered bone-mimic scaffold by blending method and in-situ mineralization to improve biological activity, which is benefit for osteoconduction, osteoinductive and the maintenance of biochemical function. The research included the crystal structure, morphology and size, distribution and retention rates of calcium minerals obtained by the two methods, and the integral structure of the mineralized scaffold. The effects of different regulatory factors on the composite scaffold were explored.
Finally, the gelation process was utilized to integrate the functional part and the structural framework through the reconstruction of hydrogen bond and crystal region. Thus, high-strength interfacial bonding was established to ensure that the scaffold can function as an entirety. The fusion effect of joint surfaces was studied; the relationship between mechanical properties and structural design was explored, and bone-mimic annular combination gels with different joint surface shapes were designed, which laid the foundation for further functional design.
In this research, a hierarchical order nanocellulose-chitosan-hydroxyapatite composite scaffold for bone defect repair was constructed through biomimetic design and self-organization. The research will also provide theoretical support for the application of natural polymers as bone tissue engineering scaffold, and will promote the new development of pulp and paper science by exploring the potential of biomedical application.

Biomimetic design and self-organizing construction of ordered nanocellulose-chitosan-hydroxyapatite composite bone defect repair scaffolds