An ideal bone repair scaffold is expected to possess superior architectural characteristics to facilitate the adhesion, proliferation, and migration of bone‐repair‐related cells, while excluding nonosteogenic cells and fibrous tissues from interfering with normal bone regeneration. Unfortunately, such scaffold material has rarely been reported. Herein, nanocomposite scaffolds with a radially ordered porous structure are presented, manufactured using a modified directional freeze‐casting method, and are promising bone defect repair materials to satisfy this requirement. The prepared nanocomposite scaffolds consist of a natural bio‐macromolecule, chitosan, and bioactive hydroxyapatite nanoparticles derived from porcine cortical bone, demonstrating favorable biocompatibility and biological functions. Both in vitro cell studies and in vivo animal studies reveal the great superiority of the radially oriented porous structure of the scaffolds in guiding bone regeneration, while simultaneously preventing the invasion of surrounding nonosteogenic cells and fibrous tissue, compared to the axially oriented porous structure. This work indicates the distinctive potential of radially oriented porous scaffolds for repairing tabular and lacunar bone defects.

Uniform and porous chitosan-based microparticles with injectable and shape-memory properties are particularly attractive due to their promising application potential for tissue engineering and regenerative medicine. However, simple and efficient methods for producing this kind of microparticle are still desirable. In this study, we report that uniform, injectable, and shape-memory chitosan microsponges were efficiently prepared by combining microfluidic emulsion with further freezing and in situ thawing processes without using any potentially cytotoxic chemical cross-linker. The produced chitosan microsponges have controllable size and could be easily injected with syringe needles. Structural observations confirmed that the chitosan microsponge had an interconnected porous structure with pore size of several micrometers and could withstand a large compressive strain of ∼93% and then recover ∼96% of its initial diameter without structural damage. The chitosan microsponges showed a high porosity (∼84%) and swelling ratio (∼3800%) as well as good antibacterial activity. Additionally, an in vitro cell coculturing investigation revealed that they also had good biocompatibility and exhibited great superiority to support cell adhesion and proliferation in three dimensions. The kind of chitosan microsponge presented here has great potential to serve as cell carriers for biomedical applications, especially as injectable scaffolds for regeneration and reconstruction of tissue defects.