可降解Fe@Fe-Zn骨组织工程支架体外生物相容性研究

目的 以多孔铁为基体，利用脉冲电沉积制备可降解多孔Fe@Fe-Zn复合材料骨组织工程支架，以期提高材料的降解速率和抗菌性能。方法 通过调节脉冲频率，得到不同Zn含量的Fe-Zn合金层;使用电子探针、X射线衍射仪、扫描电镜来研究材料的元素含量、相组成和显微结构;通过压缩测试考察支架的力学性能;用体外浸泡来考察材料的降解性能;用浸提液培养分析材料对小鼠胚胎成骨细胞的黏附铺展和细胞活性的影响;用浸提液和直接培养来探究材料的抗大肠杆菌性能。结果 随脉冲频率增加，合金中Zn含量减小;不同合金均为单一的α(Fe)相;电沉积组织致密，杂质含量低;Zn含量为7.5%(均以质量分数计)时，支架抗压屈服强度较多孔铁提升6%;复合材料的降解速率为0.44~0.48 mm/a，较多孔铁有显著改善;复合材料浸提液在稀释到25%(体积分数)时，表现出良好的细胞相容性，且随Zn含量增加，细胞活性增强;Zn含量为7.5%时，材料的抗菌性能最好。结论 通过电沉积制备的Fe@Fe-Zn支架的腐蚀速率相较于多孔铁有明显提高。随合金层中Zn含量的增加，其细胞活性增强，抗菌性能提高。Fe@Fe-Zn有望发展为可广泛应用的可降解骨组织工程支架材料。

In Vitro Biocompatibility of Biodegradable Fe@Fe-Zn Bone Tissue Engineering Scaffold

Iron-based alloys are widely studied as biodegradable materials for bone grafts or bone tissue engineering scaffolds, but their slow degradation rate may affect the repair of bone defects, and the material itself may induce local inflammation. To increase the degradation rate of porous pure iron used for bone tissue engineering scaffolds and decrease its susceptibility to inflammation, the alloying method and the electrochemical deposition technique were used to modify the porous pure iron. The zinc element with good biocompatibility and antibacterial property was adopted as an alloying element. A layer of Fe-Zn alloys was electrodeposited on the surface of the porous pure iron to prepare degradable porous Fe@Fe-Zn composite scaffolds. During electrodeposition, a porous pure iron scaffold with a pore density of 50 PPI and a working size of 60 mm × 25 mm × 3 mmwas used as the cathode and a pure iron plate with a working area of 100 mm × 47 mm was used as the anode. The working mode of electrodeposition was bipolar pulse electrodeposition. The pulse peak current density was set as 10 A/dm2 witha duty ratio of 10%, and the ratio of pulse changing direction was 20∶5. The pulse frequency of the experimental group was set as 50, 100, and 1 000 Hz, respectively, to prepare different Fe@Fe-Zn composite scaffolds, of which the zinc contents were varied. The element content, phase composition and microstructure of the composite materials were analyzed by electron probe microanalyzer (EPMA), X-ray diffractometer (XRD) and scanning electron microscope (SEM). The mechanical properties of Fe@Fe-Zn were investigated by compression test. The degradation performance of the modified materials was investigated by in vitro immersion test. The effects of different materials on the adhesion, spread and cell activity of mouse embryonic osteoblasts (MC3T3-E1) were analyzed by means of extraction culture. Finally, the anti-E.coli properties of different materials were investigated by the extract method and the direct culture method, respectively. The results showed that the Zn content of the deposited alloy layer decreased with the increase of frequency. The Fe-Zn alloys with different Zn contents had a single α(Fe) phase. The prepared Fe-Zn alloy layer was dense and well combined with the porous iron matrix. When the content of Zn in the alloy layer was 7.5% (all in terms of mass fraction), the compressive yield strength of Fe@Fe-Zn was 6% higher than that of porous iron. The results of in vitro immersion test showed that the degradation rate of the Fe@Fe-Zn group was significantly improved than that of the controlled porous iron group (the corrosion rate of Fe@Fe-Zn composites was in the range of 0.44 ~ 0.48 mm/a, and that of porous Fe was 0.33 mm/a). The results of CCK-8 test showed that the cell number increased gradually with the extension of culture time, the cell viability of the Fe@Fe-Zn group was better than that of the porous iron group, and the cell viability of the Fe@Fe-Zn cell was the best when the zinc content of alloy layer was 7.5%. Fluorescence staining showed that the cell spreading ability of the Fe@Fe-Zn group was better than that of the controlled porous iron group. Regarding antibacterial activity, all the antibacterial rates of the Fe@Fe-Zn group were greater than 50%, and the best one obtained from the Fe@Fe-Zn sample with 7.5% Zn content was (67.0±1.1)%. In conclusion, compared with the porous pure iron, the comprehensive properties of the porous Fe@Fe-Zn composite prepared by electrodeposition are significantly improved. The corrosion rates of Fe@Fe-Zn composite material scaffolds prepared by electrodeposition are greater than pure iron scaffolds. With the increase of Zn content in the deposited alloy layer, the cell activity of the material is more obvious, and the antibacterial property is gradually improved. The Fe@Fe-Zn composite has great potential as a biodegradable material for bone tissue engineering scaffolds.