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Shuai C, et al.

(A) (B)

(C) (D)

Figure 5. The morphologies of Escherichia coli cultured on (A, B) PHBV and (C, D) PHBV/5%nMgO scaffolds after 24 h.
role in exerting the antibacterial activity of some metallic promoted the production of ROS.
oxide including nMgO [44–46] . Hence, the production of The production of ROS may be attributed to a
ROS from the PHBV/nMgO scaffolds was indirectly sequential oxidation-reduction reactions occurred at the
determined by calculating the reduction percentage surface of nMgO . In detail, nMgO could be hydrated
[47]
of NBT. As shown in Figure 6, there was almost no with water and form Mg(OH) on its surface, leading
2
reduction of NBT for PHBV scaffolds, indicating they to the formation of surface bound electron-hole pairs,
did not produce ROS. Actually, a slight reduction of which would subsequently decompose into surface
ROS could be observed, which was resulted from the trapped electrons and localized holes [48,49] . They were
decomposition of NBT itself as shown in the blank typical oxide catalysts and would promote molecular
control. In contrast, there happened significant reduction oxygen (O ) to produce ROS via single electron
2
[50]
of NBT for the PHBV/nMgO scaffolds. Meanwhile, the reduction . It was worth noting that ROS was a strong
reduction of NBT gradually increased with incubation oxidant. When its concentration exceeded the scavenging
time increasing. The results demonstrated nMgO ability of the antioxidant defense system of bacteria,

Figure 6. Reduction percentage of NBT with different incubation time for PHBV/5%nMgO and PHBV

International Journal of Bioprinting (2018)–Volume 4, Issue 1 7