Multi-stage controllable degradation of strontium-doped calcium sulfate hemihydrate-Tricalcium phosphate microsphere composite as a substitute for osteoporotic bone defect repairing: Degradation behavior and bone response

Various requirements for the repair of complex bone defects have motivated to development of scaffolds with adjustable degradation rates and biological functions. Tricalcium phosphate and calcium sulfate are the most commonly used bone repair materials in the clinic, how to better combine tricalcium phosphate and calcium sulfate and play their greatest advantages in the repair of osteoporotic bone defect is the focus of our research. In this study, a series of scaffolds with multistage-controlled degradation properties composed of strontium-doped calcium sulfate (SrCSH) and strontium-doped tricalcium phosphate microspheres (Sr-TCP) scaffolds were prepared, and their osteogenic activity, in vivo degradation and bone regeneration ability in tibia of osteoporotic rats were evaluated. In vitro studies revealed that different components of SrCSH/Sr-TCP scaffolds significantly promoted the proliferation and differentiation of MC3T3-E1 cells, which showed a good osteogenic induction activity. In vivo degradation results showed that the degradation time of composite scaffolds could be controlled in a large range (6-12 months) by controlling the porosity and phase composition of Sr-TCP microspheres. The results of osteoporotic femoral defect repair showed that when the degradation rate of scaffold matched with the growth rate of new bone, the parameters such as BMD, BV/TV, Tb.Th, angiogenesis marker CD31 and new bone formation marker OCN expression were higher, which promoted the rapid repair of osteoporotic bone defects. On the contrary, the slow degradation rate of scaffolds hindered the growth of new bone to a certain extent. This study elucidates the importance of the degradation rate of scaffolds for the repair of osteoporotic bone defects, and the design considerations can be extended to other bone repair materials, which is expected to provide new ideas for the development of tissue engineering materials in the future.

Influence of bandsawing processing parameters on the preparation of cortical bone flake

Natural cortical bone is an important source of bionic bone repair materials. Sawing cortical bone is the first and important process in fabrication bone repair materials. However, the high sawing temperature could cause damage to bone tissue and nerves, and surface roughness should decrease osteoinductivity. In order to improve the cutting performance during sawing cortical bone, and the quality of prepared cortical bone slices, the band sawing process should be investigated and improved. In this paper, the novel cortical bone sawing experiment was designed with different feed rate and tooth pitch. Then, the influence of experimental parameters on temperature and roughness were analyzed with Analysis of Variance (ANOVA). The experimental results show that the lowest value of temperature is 35.5°C (tooth pitch is 8.46 mm, feed rate is 35 mm/s), the highest one is 73.8°C (tooth pitch is 4.20 mm, feed rate is 5 mm/s). And the turning point of surface roughness appear when the feed rate is 20 mm/s. Otherwise, the prediction model of sawing temperature and surface roughness could help to find optimal band sawing parameters of natural cortical bone.

Synthesis and properties of Sr2+ doping α-tricalcium phosphate at low temperature

Strontium has been widely used in bone repair materials due to its roles in promoting osteoclast apoptosis and enhancing osteoblast proliferation. In this work, synthesis and the effects of Sr2+ doping α-tricalcium phosphate at low-temperature was studied. The setting time and the mechanical properties of α-tricalcium phosphate were controlled by varying the content of Sr2+. The synthesized compounds were evaluated by XRD, SEM, XPS, setting time, compressive strength, SBF immersion, and colorimetric CCK-8 assay. The results showed that Sr2+ can improve the compressive strength and cell activity of calcium phosphate bone cement.

Application of Femtosecond Laser Microfabrication in the Preparation of Advanced Bioactive Titanium Surfaces

The surface activation of titanium plays a key role in the biological properties of titanium implants as bone repair materials. Improving the ability of apatite precipitation on the surface was...

The Effect of Magnetic Poly(lactic-co-glycolic acid) Microsphere-Gelatin Hydrogel on the Growth of Pre-Osteoblasts Under Static Magnetic Field

A number of bone repair materials are demanded due to bone injury in clinical treatment. Magnetic hydrogels combined with the magnetic field have showed great promoting potential in the field of bone regeneration. Considering the superiority of magnetic microspheres in magnetic localization and drug release, magnetic poly(lactic-co-glycolic acid) microspheres, obtained by electrospraying, were combined with gelatin hydrogel to construct a magnetic poly(lactic-co-glycolic acid) microsphere-gelatin hydrogel for bone repair in our study. Particularly, we investigated the combined effect of 20 mT static magnetic field and magnetic poly(lactic-co-glycolic acid) microsphere-gelatin hydrogel on the proliferation of MC3T3-E1 pre-osteoblasts, indicating that it could significantly promote cell growth at a low concentration of Fe3 O4. Furthermore, the hydrogel containing 400 mg˙ L–1Fe3 O4 presented the highest growth-promoting effect under a 20 mT static magnetic field. Therefore, the magnetic poly(lactic-co-glycolic acid) microsphere-gelatin hydrogel possesses impressive application value in promoting osteogenesis and bone repair.

Strontium-substituted sub-micron bioactive glasses inhibit ostoclastogenesis through suppression of RANKL-induced signaling pathway

Strontium-substituted bioactive glass (Sr-BG) has shown superior performance in bone regeneration. Sr-BG-induced osteogenesis has been extensively studied; however, Sr-BG-mediated osteoclastogenesis and the underlying molecular mechanism remain unclear. It is recognized that the balance of osteogenesis and osteoclastogenesis is closely related to bone repair, and the receptor activators of nuclear factor kappaB ligand (RANKL) signaling pathway plays a key role of in the regulation of osteoclastogenesis. Herein, we studied the potential impact and underling mechanism of strontium-substituted sub-micron bioactive glass (Sr-SBG) on RANKL-induced osteoclast activation and differentiation in vitro. As expected, Sr-SBG inhibited RANKL-mediated osteoclastogenesis significantly with the experimental performance of decreased mature osteoclasts formation and downregulation of osteoclastogenesis-related gene expression. Furthermore, it was found that Sr-SBG might suppress osteoclastogenesis by the combined effect of strontium and silicon released through inhibition of RANKL-induced activation of p38 and NF-κB pathway. These results elaborated the effect of Sr-SBG-based materials on osteoclastogenesis through RANKL-induced downstream pathway and might represent a significant guidance for designing better bone repair materials.