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In situ mineralization is a promising strategy to mimic the physicochemical properties of biominerals and is widely applied in the field of bone repair. Given the high requirement for substance exchange in cranial bone regeneration, in situ mineralized organic–inorganic hybrid materials exhibit advantages. However, the integration of remarkable mineral content, mechanical properties, and osteogenic properties also remains a major challenge. Herein, enhanced in situ mineralization through combining the enzymatic and anion‐boosted mineralization is applied to promote the mineralization efficiency, mineral content, and mechanical properties. Based on the results of computational calculations and in vitro mineralization experiments, the mechanism of mineralization enhancement is investigated from the perspectives of nucleation sites and the saturation of in situ mineralization. Anionic polyaspartic acid (pAsp) can increase the saturation of in situ mineralization; enzymatic mineralization shows high efficiency, with minerals of low crystallinity. The changes in the properties of the minerals effectively enhance the biological properties of 3D‐printed scaffolds, as confirmed by cell proliferation/differentiation experiments in vitro and in cranial bone regeneration in vivo. This strategy provides a new thinking for the preparation of bionic mineralized scaffolds for cranial bone repair, and can greatly promote the efficiency of bone regeneration. [ABSTRACT FROM AUTHOR]

• Interactions between BMP-2 and graphene variants studied by molecular dynamics. • Surface modification with O or N enhances interactions due to surface polarity. • Graphene oxide interacts with 2 epitopes of BMP-2, with highest adsorption energy. Graphene and functionalized graphene are intensively studied as biomaterials for bone repair and regeneration. The interactions between graphene/functionalized graphene and key proteins implicated in bone repair are a key event for these applications, but the underlying mechanisms are insufficiently understood. Therefore, we performed molecular dynamics method to study the interactions between bone morphogenetic protein-2 (BMP-2) and perfect graphene, reduced graphene oxide, graphene oxide, and nitrogen functionalized graphene. Results indicated that, the surface modification with oxygen or nitrogen atoms can enhance the interactions between BMP-2 and those surfaces, as a result of the modified surface polarity. Of the four materials studied, graphene oxide was calculated to have the highest adsorption energy for BMP-2, as both the wrist and knuckle epitopes of this protein can interact with the graphene oxide due to its undulated surface morphology at molecular scales. [ABSTRACT FROM AUTHOR]

• PDA/PLL hybrid coatings were developed to functionalize hydroxyapatite scaffolds. • The hybrid coatings realize tunable and sustained release of BMP2. • The hybrid coatings promote BMSC adhesion and differentiation. • The coating-functionalized scaffolds possess excellent osteoinductive properties. The scaffold for bone tissue engineering should possess proper porosity, adequate mechanical properties, cell affinity for cell attachment, and the capability to bind bioactive agents to induce cell differentiation. In this study, we successfully prepared a porous hydroxyapatite (HA) scaffold that is functionalized by poly(L-lysine)/polydopamine (PLL/PDA) hybrid coating. The PLL/PDA coating takes advantages of the high protein and cell affinity of PDA, as well as the biodegradability of PLL. Therefore, the coating can anchor bone morphogenic protein-2 (BMP2) to the HA scaffold via catechol chemistry under a mild condition so as to protect the bioactivity of BMP2. Meanwhile, the coating can also release BMP2 in a tunable and sustainable manner as the PLL degrades in the physiological environment. The BMP2-entrapped PLL/PDA coating on the HA scaffold can more efficiently promote osteogenic differentiation of bone marrow stromal cells (BMSCs) in vitro and induce ectopic bone formation to a much greater level in vivo compared with a bare HA scaffold that delivers BMP2 in a burst manner. All of these results suggest that the PDA-mediated catechol modification of the HA scaffold can be an effective strategy to develop sustainable protein delivery system, and that the PLL/PDA-coated HA scaffold could be a promising candidate for bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

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]