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The regeneration of flat bone present great challenges owing to the unique metabolic orientation and the great demand for nutrient transport. Reasonable structural design can effectively improve the performance of tissue regeneration of the scaffolds. In this study, bioactive hydroxyapatite scaffolds with various flow channel designs were precisely produced by 3D printing. The mechanical properties, permeability, substance transport and tissue ingrowth capacity brought by flow channel were investigated. Theoretical simulations and experimental results showed that the mechanical properties were highly correlated with the porosity of the scaffolds rather than the flow channel configurations. Curved channel showed a higher permeability for its better ability of omnidirectional diffusion, enhancing the substance transport and cell settlement by forming vortex flow. The flow channel scaffolds had better tissue ingrowth capability due to the abundant blood supply and cells/nutrients enrichment. Especially, the curved flow channel coupling with the annular one showed the best comprehensive performance in all the configurations designed, leading to the efficiency improvement of tissue ingrowth and bone regeneration. This study proposed preliminary principles for the design of planar two-dimensional flow channel based on the characteristics of flat bone, which provided a potential feasible strategy for large-scale flat bone regeneration and repair. [Display omitted] • Flow channel can enhance the substance transport and tissue ingrowth in flat bone repair. • Curved channel shows a higher permeability due to the omnidirectional diffusion. • Curved flow channel coupling with the annular one presents the best performance. [ABSTRACT FROM AUTHOR]

Biomimetic mineralization has been widely applied in the preparation of bone repair materials for achieving better mechanical and biological properties. However, the mineralization effectiveness is not quite satisfactory. Herein, enhanced biomimetic mineralization was realized through polyphosphate modification of gelatin. Molecular dynamics simulations theoretically demonstrated the effectiveness of poly-phosphorylation in augmenting mineralization. Experimental results revealed that poly-phosphorylation could increase the saturation of in-situ mineralization of gelatin from about 25% to more than 40%. Consequently, the compressive strength and elastic modulus of the enhanced mineralized composite were increased by 57.93% and 132.55%, respectively. The osteogenesis was also promoted. Combined with 3D printing, the scaffolds not only had the advantages of enhanced in-situ mineralization but also were endowed with the macro-controllable porous structure to achieve better bone regeneration. It interpreted the mechanism of biomimetic mineralization in terms of the saturation of in-situ mineralization and provided a viable strategy for biomimetic scaffold preparation. Enhanced biomimetic mineralization is achieved through effective in-situ mineralization of polyphosphate modified gelatin. Experiments verify that poly-phosphorylation could increase the saturation of gelatin mineralization from about 25% to more than 40%, by providing more nucleation sites of hydroxyapatite. Combined with 3D printing, the scaffolds are endowed with controllable porous structure, which offers a new avenue to manufacture bone regenerative scaffolds biomimetically. [Display omitted] • Enhanced biomimetic mineralization of organic-inorganic composites was achieved by efficient mineralization of piGel. • It theoretically and experimentally demonstrated the effectiveness of poly-phosphorylation in augmenting mineralization. • The view of saturation of in-situ mineralization was first proposed to interpret the mechanism of enhanced mineralization. • The mechanical and biological properties of enhanced-mineralized nanocomposites were improved greatly. • 3D printing was applied to achieve the construction of the personalized scaffolds. [ABSTRACT FROM AUTHOR]

Bone defect caused by trauma, tumor, infection, and other reasons is a thorny problem that needs to be solved in orthopedic clinic. Customized bone repair biomaterials and their fabrication still need to be explored. Three-dimensional (3D) printing is a high-speed fabrication process for bone tissue biomaterials, which paves the way of solving clinical bone defect problems in a new way. In this study, the fused deposition modeling (FDM) technology was used to prepare the composite scaffolds of polylactic acid (PLA) and nano-hydroxyapatite (n-HA). The composite scaffold was optimized by material characterization, mechanical property test, and in vitro bone marrow mesenchymal stem cells biocompatibility test. Finally, a rabbit model was established to evaluate the osteogenic ability of PLA/n-HA scaffolds in vivo. The results showed that the PLA/n-HA composites proposed in this study were highly printable, and the printed scaffold showed tunable mechanical strength accompanied by the proportion of n-HA components. The biocompatibility and osteogenic induction properties were proved better than that of the pure PLA scaffold. This composite scaffold of PLA and n-HA provides a promising strategy for the repair of large bone defects. [ABSTRACT FROM AUTHOR]