A facile approach to construct ferroferric oxide/chitosan composite scaffolds with three-dimensional oriented structure has been explored in this research. Chitosan and ferroferric oxide are co-precipitated by using an in situ precipitation method, and then lyophilized to get the composite scaffolds. XRD indicated that Fe304 was generated during the gel formation process, and increasing the content of magnetic particles could destruct the crystal structure of chitosan. When the content of magnetic particles is lower than 10%, the layer-by-layer structure and wheel spoke structure are coexisting in the scaffolds. Increasing the content of magnetic particles, just layer-by-layer structure could be observed in the scaffolds. Ferroferric oxide particles were uniformly distributed in the matrix, the size of which was about 0.48 gm in diameter, 2 gm in length. Porosity of magnetic chitosan composite scaffolds is about 90%. When the ratio of ferroferric oxide to chitosan is 5/100, the compressive strength of the material is 0.4367 MPa, which is much higher than that of pure chitosan scaffolds, indicating that the layer-by-layer and wheel spokes complex structure is beneficial for the improvement of the mechanical properties of chitosan scaffolds. However, increasing the content of ferroferric oxide, the compressive strength of scaffolds decreased, because of the decreasing of chitosan crystallization and aggregation of magnetic particles as stress centralized body. Another reason is that the layer-by-layer and wheel spokes complex structure makes bigger contributions for the compressive strength than the layer-by-layer structure does. Three-dimensional ferroferric oxide/chitosan scaffolds could be used as hyperthermia generator system, improving the local circulation of blood, promoting the aggradation of calcium salt and stimulating bone tissue regeneration.
In an effort to develop biomaterials to meet guided tissue regeneration （GTR） standards for periodontal tissue recovery, a homogeneous and transparent chitosan （CS）/hydroxyapatite （HA） membrane with potential applications as GTR barrier in periodontal therapy has been prepared via in situ compositing. The membrane has been designed to have a smoothrough asymmetric structure that meets the demand for GTR. Component and morphology of the membrane are characterized by XRD and SEM. It can be indicated that HA was in situ synthesized uniformly in the CS membrane. Mechanical experiments of the membranes with various HA contents show that their tensile strengths are adequate for periodontal therapy. Biological properties of the membrane have been performed by cell toxicity assays, hemolysis tests and animal experiments. Results indicate that the membrane has good biocompatibility and inductive effect for cell growth. Therefore this membrane can be potentially applied as GTR barrier membrane for periodontal tissue regeneration.
Multi-walled carbon nanotubes （MWNTs） and chitosan （CS） composite rods with layer-by-layer structure were prepared via in situ precipitation method. On the one hand, some MWNTs fragments with open tips played the role of nuclear agent to improve the crystallinity of CS. On the other hand, MWNTs embedded in CS matrix to absorb energy when the composite rods were destroying. Nanotubes pulled out from CS matrix, and lots of holes remained, so MWNTs could endure external stress effectively. The bending strength and bending modulus of CS/MWNTs rods （100/0.5, W/W） arrived at 130.7 MPa and 4.4 GPa respectively, increased by 34.3% and 7.3% compared with those of pure CS rods. Consequently, CS/MWNTs composite rods with excellent mechanical properties could be a novel device used for bone fracture internal fixation.
