Page 313 - IJB-10-4

International Journal of Bioprinting PCL/Fe3O4@ZIF-8 for infected bone repair

0.99, 1.85, and 2.84 emu/g, respectively, which indicated Moreover, the morphology and adhesion of S. aureus
that the addition of Fe O @ZIF-8 nanoparticles enhanced and E. coli on the surface of scaffolds were visualized by
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the saturation magnetization of the scaffolds. In addition, SEM. For both microorganisms, the number of bacteria
the low coercivity and remanence of the scaffolds indicated adherent on the surfaces of the PCL/Fe O @ZIF-8 scaffolds
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that they possessed superparamagnetic character (Figure was significantly less than that on the surface of PCL
2G), which contributed to their fast magnetic response. scaffolds (Figure 3E–H). Furthermore, the collapsed and
ruptured bacterial membranes were seen on the surfaces of
As shown in Figure 2H, Zn ions were slowly
2+
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released from the PCL/Fe O @ZIF-8 scaffolds for more the PCL/Fe O @ZIF-8 scaffolds, signifying bacterial death.
The SEM results indicated that the bactericidal mechanism
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than 7 days, without a burst-release. It was found that of PCL/Fe O @ZIF-8 scaffolds may be related to bacterial
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there was a small, acute Zn release in the first 12 h, cell membrane disruption, which could be attributed to the
2+
and 0.42, 0.59, and 0.79 μg/mL of Zn were released binding of bacteria membrane protein and Zn released
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from PCL/5%Fe O @ZIF-8, PCL/10%Fe O @ZIF-8, and continuously from the Fe O @ZIF-8 scaffolds.
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PCL/15%Fe O @ZIF-8 at 12 h, respectively. After 2 days, 3 4
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the release rate gradually decreased. Until the seventh 3.4. Biocompatibility of PCL/Fe O @ZIF-8 scaffolds
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day, the concentrations of the released Zn were 0.60, The flow cytometry results showed that cultured BMSCs
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1.06, and 1.25 μg/mL, respectively. TGA results indicated were positive for surface markers including CD29 (99.6%)
that PCL/Fe O @ZIF-8 had a lower thermal stability than and CD90 (99.5%), and negative for CD31 (0.5%) and
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pure PCL (Figure S1 in Supplementary File). PCL/Fe O @ CD45 (0.3%) (Figure S2 in Supplementary File). To
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ZIF-8 scaffolds were stable at temperature between 30 evaluate the biocompatibility of the scaffolds, BMSCs
and 250°C, and the sharp weight loss happened at 250 to were co-cultured with the scaffolds as per procedures
320°C, while the sharp weight loss of pure PCL happened illustrated in Figure 4A. According to CCK-8 results, the
at 360°C. Compared to the TGA results of Fe O @ZIF-8 proliferation rates in all groups increased with time from
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nanoparticles, the decomposition temperatures of PCL/ day 1 to day 7 (Figure 4B). In addition, the proliferation
Fe O @ZIF-8 scaffolds (250°C) and pure PCL (360°C) rate of BMSCs co-cultured with PCL/10%Fe O @ZIF-8
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were lower than ZIF-8 (380°C) and Fe O @ZIF-8 (350°C). scaffolds was significantly increased compared to the blank
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Thus, we considered that the weight loss of PCL/Fe O @ control group and PCL group at all time points (p < 0.001).
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ZIF-8 scaffolds at temperature 250°C was attributed to the However, the proliferation rate of BMSCs in the PCL/15%
decomposition of PCL and Fe O @ZIF-8 bonding. Fe O @ZIF-8 group was decreased compared to that in the
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blank control group, indicating that high concentration of
3.3. Antibacterial activities of PCL/Fe O @ZIF-8 Fe O @ZIF-8 nanoparticles had an adverse influence on
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scaffolds in vitro the biocompatibility of the scaffolds.
S. aureus (Gram-positive bacteria) and E. coli (Gram-
negative bacteria) are the most common microorganisms Moreover, cell adhesion to scaffolds was evaluated
contributing to bone infection. After the bacteria were co- by immunofluorescence staining, through which the
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cultured with different groups of scaffolds, the number of S. cytoskeleton was stained in red with rhodamine, and the
aureus and E. coli colonies on agar plates (Figure 3A and B) cell nuclei were stained in blue with DAPI. As shown in
and the statistic results of CFU colonies (Figure 3C and D) Figure 4C and Figure S3 (Supplementary File), more
indicate that the CFU counts for both two pathogens cells were attached to the surface of PCL/10%Fe O @
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ZIF-8 scaffolds than other scaffolds, a finding consistent
were significantly lower in the PCL/Fe O @ZIF-8 groups with the CCK-8 results. These results indicated that
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compared with the PCL group, and CFU counts were PCL/10%Fe O @ZIF-8 scaffolds had the strongest ability
significantly decreased with the increasing concentration to promote cell proliferation and the best biocompatibility.
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of Fe O @ZIF-8 nanoparticles in the PCL/Fe O @ZIF-
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8 scaffolds (p < 0.001). The anti-bacterial adhesion 3.5. Osteogenic differentiation of BMSCs co-cultured
efficiencies of PCL/5%Fe O @ZIF-8, PCL/10%Fe O @ZIF- with PCL/Fe O @ZIF-8 scaffolds in vitro
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8, and PCL/15%Fe O @ZIF-8 scaffolds against S. aureus To evaluate the osteogenesis ability of PCL/Fe O @
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were 40.13%, 63.03%, and 83.49%, respectively, and the ZIF-8 scaffolds, BMSCs were co-cultured with scaffolds
efficiencies against E. coli were 43.28%, 71.58%, and 92.69%. in osteogenic induction medium, and divided into
In summary, PCL/Fe O @ZIF-8 scaffolds possessed control group, PCL group, PCL/5%Fe O @ZIF-8 group,
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higher level of antibacterial activities compared with PCL PCL/10%Fe O @ZIF-8 group, and PCL/15%Fe O @ZIF-
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scaffolds, and the anti-bacterial adhesion efficiency of 8 group. ALP activity measurement, ALP staining, and
scaffolds was increased with increasing concentration of alizarin red staining were performed after induction. The
Fe O @ZIF-8 nanoparticles loading. expressions of osteogenic-related genes and proteins,
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Volume 10 Issue 4 (2024) 305 doi: 10.36922/ijb.2271