PURPOSE In this study, pore size and porosity distribution of porous Ti-6Al-4V scaffolds (pTi) were controlled by 3D printing. The effects of pore size distribution at a constant porosity, or porosity distribution at a constant pore size pertaining to functions of adhesion, proliferation, and differentiation of the mouse embryonic osteoblast precursor (MC3T3-E1) cells were researched separately. METHODS 3D printing was used to design five groups of pTi, designated as PS300/HP, PS300/LP, PS500/HP, PS500/LP, and PS800/HP based on pore size and porosity distribution. MC3T3-E1 cells were cultured on pTi, and non-porous Ti-6Al-4V samples (npTi) were prepared as control. The pTi was characterized with the scanning electron microscopy (SEM). MC3T3-E1 cells were stained via AlamarBlue assay and viability and proliferation analyzed. The mRNA levels of alkaline phosphatase (ALP), osteocalcin (OCN), collagentype-1 (Col-1), and runt-related transcription factor 2 (Runx2) in MC3T3-E1 cells were analyzed by real-time PCR analysis. RESULTS The average pore size and porosity of pTi were recorded as (301 ± 9 μm, 58.8 ± 1.8%), (300 ± 9 μm, 43.4 ± 1.3%), (501 ± 11 μm, 58.3 ± 1.2%), (499 ± 12 μm, 42.7 ± 1.1%), and (804 ± 10 μm, 58.9 ± 1.3%), respectively. SEM images confirmed active attachment of cells and oriented with the direction of metal rod after pTi/MC3T3-E1 co-culture for 3 and 7 days. In addition, MC3T3-E1 cells grown on the PS800/HP displayed significantly higher proliferation compared with each group after 3 days incubation (p < 0.05). Moreover, cells showed some degree of proliferation in all groups, with the highest value recorded for PS800/HP after culture for 7 days (p < 0.05). The gene expression pattern of ALP, OCN, Col-1, and Runx2 confirmed that these were down-regulated when pore size increased or porosity decreased of pTi (p < 0.05). CONCLUSION The pTi facilitated the adhesion and differentiation of osteoblast when pore size decreased or porosity increased. The scaffold model resembles physical modification with porous structures, which has potential application in the surface modifications of Ti implant.

中文翻译：

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通过 3D 打印整合 Ti-6A1-4V 支架上的孔径和孔隙率分布以调节骨分化

目的 在本研究中，通过 3D 打印控制多孔 Ti-6Al-4V 支架 (pTi) 的孔径和孔隙率分布。分别研究了恒定孔隙率下的孔径分布或恒定孔径下的孔隙率分布对小鼠胚胎成骨细胞前体（MC3T3-E1）细胞的粘附、增殖和分化功能的影响。方法基于孔径和孔隙率分布，采用3D打印设计5组pTi，分别命名为PS300/HP、PS300/LP、PS500/HP、PS500/LP和PS800/HP。MC3T3-E1 细胞在 pTi 上培养，制备无孔 Ti-6Al-4V 样品 (npTi) 作为对照。pTi 用扫描电子显微镜 (SEM) 表征。MC3T3-E1 细胞通过 AlamarBlue 测定染色并分析活力和增殖。通过实时 PCR 分析分析 MC3T3-E1 细胞中碱性磷酸酶 (ALP)、骨钙素 (OCN)、collagentype-1 (Col-1) 和 runt 相关转录因子 2 (Runx2) 的 mRNA 水平。结果 pTi的平均孔径和孔隙率记录为（301±9μm，58.8±1.8％），（300±9μm，43.4±1.3％），（501±11μm，58.3±1.2％），（499 ± 12 μm, 42.7 ± 1.1%) 和 (804 ± 10 μm, 58.9 ± 1.3%)。pTi/MC3T3-E1 共培养 3 天和 7 天后，SEM 图像证实了细胞的活跃附着并与金属棒的方向一致。此外，与各组相比，在 PS800/HP 上生长的 MC3T3-E1 细胞在孵育 3 天后显示出显着更高的增殖（p < 0.05）。此外，所有组的细胞都表现出一定程度的增殖，培养 7 天后 PS800/HP 记录的最高值 (p < 0.05)。ALP、OCN、Col-1 和 Runx2 的基因表达模式证实，当 pTi 的孔径增加或孔隙率降低时，这些基因表达下调（p < 0.05）。结论当孔径减小或孔隙率增加时，pTi促进成骨细胞的粘附和分化。该支架模型类似于具有多孔结构的物理改性，在钛植入物的表面改性中具有潜在应用。