Amorphous calcium carbonate (ACC) plays a crucial role in biomineralization which crystallization process has attracted significant attention. Magnesium ions (Mg²⁺) can effectively regulate the crystallization of ACC, but the mechanism by which it controls the transformation of ACC into monohydrocalcite (MHC, CaCO₃·H₂O) is not well understood. In this study, Mg²⁺ was used as an additive, and the transformation process from ACC to MHC was investigated in situ using an automatic potentiometric titration system. It was found that Mg²⁺ can enhance the stability of ACC and inhibit the formation of calcite and vaterite. During the transformation of ACC to MHC, partial dissolution firstly occurred, and the molar ratio of Mg/Ca in the solution increased with the consumption of Ca²⁺. Mg²⁺ further adsorbed onto the surface of ACC particles, inhibiting surface dissolution of ACC and promoting internal dissolution of ACC, resulting in the formation of hollow structures rich in Mg²⁺ and smaller-sized nanoparticles. Subsequently, MHC crystallized and grew through particle aggregation. These results elucidate the mechanism by which Mg²⁺ regulates the transformation of ACC into MHC through a non-classical crystallization pathway, enhancing an understanding of the biomineralization mechanism from ACC precursor.

Bioceramics have attracted extensive attention for bone defect repair due to their excellent bioactivity and degradability. However, challenges remain in matching the rate between bioceramic degradation and new bone formation, necessitating a deeper understanding of their degradation properties. In this study, density functional theory (DFT) calculations was employed to explore the structural and electronic characteristics of silicate bioceramics. These findings reveal a linear correlation between the maximum isosurface value of the valence band maximum (VBM_Fmax) and the degradability of silicate bioceramics. This correlation was subsequently validated through degradation experiments. Furthermore, the investigation on phosphate bioceramics demonstrates the potential of this descriptor in predicting the degradability of a broader range of bioceramics. This discovery offers valuable insights into the degradation mechanism of bioceramics and holds promise for accelerating the design and development of bioceramics with controllable degradation.

Hydroxyapatite (HAP), as a common bone repair material, still faces the risk of bacterial infection in the treatment of infectious bone defects, whose limited osteogenic properties also hinders its further application. This study used a coprecipitation method to prepare the manganese doped hydroxyapatite nanorod (MnHAP), which exhibited excellent cell biocompatibility, high antibacterial efficiency and osteogenic properties. Antibacterial experiments showed that the inhibition rates of MnHAP10(n(Mn)/n(Ca+Mn)=10%)) against Escherichia coli and Staphylococcus aureus can reach 77.85% and 75.92%, respectively. Moreover, the antibacterial efficiency of MnHAP10 against Escherichia coli can be further enhanced (97.63%) under 808 nm near-infrared light irradiation. Cell proliferation and related osteogenic gene experiments display that MnHAP is beneficial for the proliferation and differentiation of osteoblasts, which improves protein adsorption capacity, stimulates osteogenic activity, and promotes the expression of related osteogenic genes, demonstrating its good biocompatibility. Therefore, MnHAP nanorods are expected to provide a new approach in the treatment of infectious bone defects.

The question of what qualities excellent medical bioceramics must possess to ensure satisfactory prognosis for bone healing and reconstruction remains a topic of great interest in both clinical and biomaterial sciences. Our team has been dedicated to researching medical bioceramics since the 1990s, involving basic scientific research, applied translational research, and clinical trials. Consequently, we have amassed a wealth of research and implementation experience. In this article, we aim to explore the subject of “Functional Bioadaptability in Medical Bioceramics”, specifically focusing on calcium phosphate-based materials. We summarized how to effectively combine bioadaptability with design and manufacturing of medical bioceramics in the background of orthopedic clinical application, with the following aspects of structural adaptability, degradative adaptability, mechanical adaptability, and application adaptability. Hopefully, some suggestions put forward can ultimately provide valuable insights and recommendations for the design, production, supervision, and application of the upcoming medical bioceramics.

Archaeological weathered bones are usually porous and fragile, easily to warp, crack and crumble. To avoid these relic damages, consolidation technology is badly needed. Here, we explored a new consolidation method for weak bone relics using hydroxyapatite as protectant. Briefly, dispersion of calcium oxide mixed with calcium hydrophosphate in alcohol was used firstly to permeate into the fragile bones as precursor of hydroxyapatite consolidant. Then pure water was used to trigger the reaction between calcium oxide and calcium hydrophosphate, which leads to formation of a continuous phase of hydroxyapatite consolidant. By filling and bridging the pores or fissure inside the fragile bones, hydroxyapatite consolidant can act as a reinforcement material. Effects of the mass ratio of calcium oxide to calcium hydrophosphate (1 : 1, 1 : 3, 1 : 4, 1 : 5, 1 : 6, 1 : 7) and the application ways (brushing, drip infiltration and soaking) on the protective performance were investigated by scanning electron microscope (SEM), energy dispersive spectroscope (EDS), X-ray diffraction (XRD) and characterizations of color difference, weight increment, porosity, density and cohesive strength determination. The results showed that the best consolidation performance could be obtained when the mass ratio of 1 : 3 and the brushing consolidation method were adopted. In this case, porosity of the fragile bones decreased by 17.3%. Mass, density and cohesive strength of the fragile bones increased by 38.39%, 34.49% and 16.32%, respectively. Moreover, the color difference of bones is less than 3.0, which is allowable in the field of heritage conservation.

Titanium and its alloys have been widely used as hard tissue implants due to their excellent mechanical properties and biocompatibilities. However, the lack of biological activity on its surface and the inflammatory reaction after implantation can easily lead to unsatisfactory osseointegration. In this work, the wettability of titanium oxide coatings was modulated by annealing in different atmospheres, and the effects of surface wettability on polarization of macrophages and osteogenic differentiation of mBMSCs were studied. The results showed that, compared to the hydrophilic titanium oxide coating (~10º, PEO-A), the titanium oxide coating with contact angle about 90º (PEO-A-V) inhibited the polarization of macrophages towards M1 pro-inflammatory direction under the mono-culture condition. However, under the co-culture condition, the titanium oxide coating with contact angle about 90º promoted macrophage polarization towards M2 and significantly upregulated gene expressions of osteogenic markers related to mBMSCs, indicating better immunomodulatory effects on osteogenic differentiation of mBMSCs.

Pulp capping agents are effective materials which can preserve dental pulp and treat caries in different ways. It is urgently demanded to establish a guidance to select the appropriate pulp capping agents according to the conditions of pulp and cary requirements. In this work, morphology, composition, physical, and chemical properties of three commonly used clinical pulp capping agents, namely dental zinc oxide eugenol cement (ZnO), self-curing calcium hydroxide (Dycal), and light-curing calcium hydroxide (Calcimol), were studied. Their antibacterial, cytocompatibility and blood compatibility were evaluated. The results showed that ZnO was hydrophobic and its effective component, crystallized ZnO, could consistently release zinc ions, giving its alkaline environment to inhibit bacteria. Structure, morphology and components in Dycal were similar to those in Calcimol. However, its surface was more hydrophobic and its release amount of calcium ions was larger than that of Calcimol. It formed an alkaline micro-environment, thereby possessed good antibacterial ability and biocompatibility. Meanwhile, Calcimol was hydrophilic and convenient to operate, and released less metal ions. Due to its safe composition, Calciomol exhibited excellent biocompatibility but slightly weaker antibacterial property. Our results suggested that these comparative results might be a useful clinical guidance for selecting appropriate pulp capping agents according to the degree of caries and the health status of dental pulp to treat the caries.

Titanium orthopaedic implants present a risk of infection and require the development of antibacterial, but still biocompatible and non-resistant coatings. Magnesium oxide (MgO) coatings were prepared on micro-arc oxidized titanium by electrophoretic deposition for 15, 30, 45, or 60 s. Nano-sized MgO particles agglomerated to form homogeneous coatings with surface coverage increasing with the duration of deposition. The four groups produced antibacterial rates of 1%, 69%, 83%, and 84% after co-cultured with S. aureus for 6 h, and 81%, 86%, 89%, and 98% after co-cultured for 24 h. Electron and fluorescence microscopies showed decreasing density of bacterial cells and proportion of living cells with increasing time of deposition. Mouse osteoblasts seeded on the four groups had survival rates of 108%, 89%, 53%, and 27% on day 1, and 139%, 117%, 112%, and 66% on day 5. Proportion of dead cells on the coated samples increased with increasing time of deposition but less than 5% on day 5. These results indicate that MgO coatings prepared by electrophoretic deposition for 30 s is reasonable in vitro antibacterial activities and cytocompatibility.

Beta tricalcium phosphate (β-TCP) ceramic substituted materials have attracted a large amount of attention in the last decades because of their chemical similarity with bone inorganic components, good biocompatibility, and osteoconductivity. Such materials can be used for bone replacement and bone formation in various forms, such as nanoparticles, scaffolds and microspheres. In this study, five different microsphere materials of tricalcium phosphate/trimagnesium phosphate (TMP) (TCP, 25% TMP, 50% TMP, 75% TMP, and TMP) composites were prepared and characterized. With the increase of TMP content in the composite microspheres, the cumulative concentration of Mg²⁺ and Ca²⁺ released from the microspheres increased, indicating that TMP can regulate the degradation rate of the composite microspheres. The osteoblast precursor cell line (MC3T3-E1 cells) and human umbilical vein endothelial cells (HUVECs) were used as models to evaluate the biocompatibility, angiogenesis and osteogenesis of the composite microspheres. The results showed that compared with TCP, TMP and 75% TMP group, 25% TMP and 50% TMP composite microspheres had better cell compatibility and had a certain proliferative effect on HUVECs. Therefore, composite microspheres of 25% TMP and 50% TMP have more significant positive effects on angiogenesis and osteogenesis.

Natural bone has a unique micro-/nano-structure, which is composed of organic nanomaterials (collagen fibers) and inorganic nanomaterials (hydroxyapatite). Thus, compared with traditional synthetic materials, natural bone has incomparable advantages in biological, functional and mechanical properties. In the research of tissue engineering and regenerative medicine, biomaterial scaffold with micro-/nano-structures simulating the characteristics of natural bone tissue are one of the research focuses. In recent years, researchers have found that micro-/nano-structured biomaterials can effectively regulate cell proliferation, differentiation and migration, and have a strong ability to promote cell osteogenic differentiation, so as to promote bone tissue regeneration in vivo. In this article, we focus on reviewing recent research progress of biomaterial design on simulating the hierarchical characteristics of natural bone, analyzing the complicated interaction between micro-/nano-structured biomaterials and cells, and summarizing their applications in bone tissue engineering to provide new ideas for the design of biomaterials.

Bioceramic scaffolds with excellent osteogenesis ability and degradation rate exhibit great potential in bone tissue engineering. Akermanite (Ca₂MgSi₂O₇) has attracted much attention due to its good mechanical property, biodegradability and enhanced bone repair ability. Here, akermanite (Ca₂MgSi₂O₇) scaffolds were fabricated by an extrusion-type 3D printing at room temperature and sintering under an inert atmosphere using printing slurry composed of a silicon resin as polymer precursor, and CaCO₃ and MgO as active fillers. Furthermore, the differences in structure, compressive strength, in vitro degradation, and biological properties among akermanite, larnite (Ca₂SiO₄) and forsterite (Mg₂SiO₄) scaffolds were investigated. The results showed that the akermanite scaffold is similar to those of larnite and forsterite in 3D porous structure, and its compressive strength and degradation rate were between those of the larnite and forsterite scaffolds, but it showed a greater ability to stimulate osteogenic gene expression of rabbit bone marrow mesenchymal stem cells (rBMSCs) than both larnite and forsterite scaffolds. Hence, such 3D printed akermanite scaffold possesses great potential for bone tissue engineering.

Borosilicate bioglass has attracted extensive attention due to its stable structure and excellent biological activity. However, the rate of its mineralization process is fast in the initial stage and slow in the middle and late stages, which limits the application of borosilicate bioglass. As an auxiliary method, the near-infrared (NIR) laser can accelerate the degradation of bioglass. Therefore, we prepared a core-shell borosilicate bioglass with titanium nitride as the core and bioglass (40SiO₂-20B₂O₃-36CaO-4P₂O₅) as the shell, and used near-infrared laser regulation technology to intervene the mineralization process of the composite bioglass. The experimental results show that the core-shell bioglass exhibits a significant photothermal effect, and the photothermal ability increases with the increases of the doping amount of TiN NPs and the laser power density. During the in vitro immersion, near-infrared laser increased the degradation rate of bioglass. After immersion for 7 d, the contents of calcium and boron in the SBF are increased by 12%-16% and 8%-11%, respectively. Meanwhile, the formation efficiency of hydroxyapatite is significantly improved. Cell proliferation activity test shows that the sample has good biological safety. Therefore, near-infrared light can accelerate the degradation and mineralization of functional core-shell bioactive glass, which is expected to play a regulatory role.