Background

Ideal bone defect repair scaffolds should be biodegradable, biocompatible, bioactive, porous, and provide adequate mechanical support. However, it is challenging to fabricate such an ideal bone repair scaffold. Previously, we showed that 5 wt.% strontium-doped hydroxyapatite (Sr-HA) scaffolds prepared by spark plasma sintering (SPS) technology exhibited good biocompatibility. Moreover, unlike pure hydroxyapatite (HA) scaffolds, HA scaffolds containing strontium (Sr) exhibited superior bioactivity, higher proliferation rate of BMSCs and MG-63 osteoblast cells, as well as enhanced BMSCs differentiation.

Methods

In this study, we prepared pure HA scaffolds and 5 wt.% strontium containing Sr-HA scaffolds by SPS technology without adhesive, ammonium bicarbonate as pore former. Subsequently, scanning electron microscope (SEM) and X-Ray diffraction (XRD) were used to characterize the properties of Sr-HA and HA scaffolds. The ability of the scaffolds to repair bone defects was evaluated using a critical-sized rabbit tibia-bone defect rabbit model. Thirty 3-month-old New Zealand white rabbits were randomly divided into three groups (blank control group, Sr-HA scaffolds implanted group and HA scaffolds implanted group) with 10 rabbits in each group. These rabbits are sacrificed after 8 weeks and 16 weeks of surgery, and the repair effects of each scaffold were evaluated with X-ray, micro-CT, and HE staining. The three-point bending test was employed to assess the mechanical property of repaired bones.

Results

XRD pattern indicated that Sr-HA and HA scaffolds possess a similar crystal structure after sintering, and that incorporation of strontium did not form impure phase. SEM showed that the porosity of Sr-HA and HA scaffolds was about 40 %. Universal Testing Machine tests showed that Sr-HA scaffolds had better compressive strength than HA scaffolds. Bone defect was obvious, and the fibrous tissue was formed in the bone defects of rabbits in the blank control group after 8 weeks of surgery. Sr-HA and HA scaffolds enhanced osteointegration of the host bone, and extensive woven bone was formed on the surface of the Sr-HA scaffolds. After 16 weeks, the bone strump became blunt and a small amount of callus was formed in the blank control group. Comparatively, the scaffolds were substantially degraded in the Sr-HA scaffolds implanted group while scaffolds shadows still were observed in the HA implanted group. Bone remodeling and cavity recanalization were completely developed in the Sr-HA scaffolds group. The compressive strength of repaired bone in the Sr-HA scaffolds implantation group was higher than that of HA scaffolds implantation group after 8 weeks and 16 weeks of surgery.

Conclusions

Our results show that the Sr-HA composite scaffolds can effectively repair bone defects and have good biodegradable properties.

中文翻译：

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通过SPS技术制造的Sr-HA支架可促进节段性骨缺损的修复。

背景

理想的骨缺损修复支架应该是可生物降解的，生物相容的，具有生物活性的，多孔的，并提供足够的机械支持。然而，制造这种理想的骨修复支架是具有挑战性的。以前，我们显示通过火花等离子体烧结（SPS）技术制备的5 wt。％掺锶羟基磷灰石（Sr-HA）支架具有良好的生物相容性。此外，与纯羟基磷灰石（HA）支架不同，含锶（Sr）的HA支架表现出优异的生物活性，更高的BMSCs和MG-63成骨细胞增殖率以及增强的BMSCs分化能力。

方法

在这项研究中，我们通过SPS技术制备了纯HA支架和5 wt。％含锶的Sr-HA支架，不含粘合剂，碳酸氢铵作为造孔剂。随后，使用扫描电子显微镜（SEM）和X射线衍射（XRD）来表征Sr-HA和HA支架的特性。使用临界大小的兔胫骨缺损兔模型评估支架修复骨缺损的能力。30只3个月大的新西兰大白兔随机分为三组（空白对照组，Sr-HA支架植入组和HA支架植入组），每组10只。在手术8周和16周后处死这些兔子，并通过X射线，micro-CT和HE染色评估每个支架的修复效果。

结果

XRD图谱表明，Sr-HA和HA支架在烧结后具有相似的晶体结构，锶的掺入不会形成不纯相。SEM显示，Sr-HA和HA支架的孔隙率约为40％。通用测试机测试表明，Sr-HA支架比HA支架具有更好的抗压强度。术后8周，空白对照组兔子的骨缺损明显，并在其骨缺损处形成了纤维组织。Sr-HA和HA支架增强了宿主骨的骨整合，并且在Sr-HA支架的表面形成了广泛的编织骨。16周后，空白对照组的骨ump变钝，形成少量骨of。比较，Sr-HA支架植入组中的支架明显降解，而在HA植入组中仍观察到支架阴影。Sr-HA支架组的骨重建和腔再通完全完成。术后8周和16周，Sr-HA支架植入组的修复骨抗压强度高于HA支架植入组。

结论

我们的结果表明，Sr-HA复合支架可以有效修复骨缺损，并具有良好的生物降解性能。