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Shuai, et al.
Meanwhile, the composition analysis of corrosion 3 Results and discussion
products was performed by EDS. The degradation
rates of samples were calculated according to the 3.1 Powder characterization and sample
methods in the literature . preparation
[35]
2.7 Cytocompatibility tests The used powders in this study are depicted
in Figure 1A-F. SEM images in Figure 1A,B
Human osteosarcoma cell line (MG-63) from the indicated that both Fe and Mg Si powders had an
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American Type Culture Collection was adopted to irregular shape and the latter exhibited smaller
evaluate the cytocompatibility of samples according particle sizes than the former. The particle size
to the indirect contact method [4,40] . The MG-63 cells distribution of Fe powder was further measured by
were first cultured in Dulbecco’s Modified Eagle’s a laser particle analyzer. It is shown in Figure 1A
Medium (DMEM) with 100 U/ml penicillin, that the particle size of Fe powder was mainly
100 mg/ml streptomycin, and 10% fetal bovine between 12 and 30 μm and the average value was
serum at 37°C under a humidified atmosphere of 27.1 ± 0.5 μm. Meanwhile, fine Mg Si particles
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5% CO . The Fe/Mg Si samples were immersed were evenly distributed in Fe powder in Figure 1C,
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2
in DMEM for 3 days with a surface area/solution which enabled Mg Si to fully exert its roles in the
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ratio of 1.25 (cm /ml) at 37°C according to the composite. Besides, XRD patterns in Figure 1E
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ISO 10993-12 . Subsequently, the supernatant showed that the only detectable phase was α-Fe
[1]
fluid was withdrawn and centrifuged for preparing with BCC structure and the (110) crystal plane had
the extract. For fluorescence staining assay, MG- the highest intensity due to the preferred crystalline
63 cells were incubated in the extracts of different orientation. For Mg Si powder, the Mg Si phase
2
2
concentrations (25, 50, and 100%) with DMEM as was identified by main diffraction peaks at 24.2°,
the control group (extract concentration of 0%) for 40.1°, and 47.3° corresponding to (111), (220), and
1, 2, and 3 days, respectively. The MG-63 cells were (311) diffraction planes, respectively, as illustrated
subsequently stained by ethidium homodimer-1 in Figure 1E. EDS analysis in Figure 1F showed
reagents and calcein-AM for 18 min, and finally that Fe and Mg Si powders were composed of Fe
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rinsed twice using phosphate-buffered solution. and Mg, Si elements, respectively, which indicated
To observe the living cells, the cells were fixed on higher purity of the powders. The mixed powders
glasses and checked using a BX60 Fluorescence of Fe and Mg Si were scanned by laser according
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Microscope (Olympus, Japan). The number of to the computer-aided design model to prepare
living cells was estimated by ImageJ software composites, as illustrated in Figure 1G. It could be
according to the fluorescent images. To evaluate found that the prepared composites have uniformly
the viability of MG-63 cells in the extracts of distributed porous structures with a diameter of
different concentrations (0, 25, 50, and 100%), 0.8 mm. The porous structures of composites
CCK-8 tests were performed for 1, 2, and 3 days, would not only accelerate Fe degradation through
respectively. After culture for the scheduled time, the increase of surface area in contact with SBF
10 μL CCK-8 solutions (5 mg/ml) were added to but also promote nutrient transport through the
the cell culture medium. Then, the absorbance was interconnected architecture.
gained by a microplate reader (BioRad, USA) at
450 nm. Cell viability was calculated since it was 3.2 Microstructure
positively correlated with the absorbance . The microstructural features of Fe/Mg Si
[41]
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2.8 Statistical analysis composites are presented in Figure 2. It is
shown in Figure 2A,E that the Fe/0.3Mg Si
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Experimental data were presented as mean ± had a compact microstructure without original
standard deviation. Symbol “*” indicates a powder particles. Meanwhile, a small amount of
significant difference (P < 0.05). Mg Si could be discernible, as evidenced by EDS
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International Journal of Bioprinting (2020)–Volume 6, Issue 1 77