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International Journal of Bioprinting Biocompatible materials and Multi Jet Fusion

these results suggest that the less robust growth of cells on evaluation of the biocompatibility of such products. For
PA-12 observed previously in our MTT assay for short-term MJF-printed materials to be used as a bioreactor, it must
culture (Figure 3B) is not due to any permanent damage to be able to support not just cell growth and proliferation,
the cells. This is consistent with our Ki-67/p53 expression but also other complex and highly regulated processes
(Figure 6A and Figures S13–S18) and oxidative stress such as osteogenesis. This study presents an examination
(Figure 5C and Figure S12) results which suggest no obvious of 3D-printed PA-12 with regard to material surface
sign of change in the proliferation profile and redox status property and biocompatibility. Our results indicate that
of cells grown on PA-12. Moreover, 3D-printed PA-12 in the MJF-printed PA-12 can be considered appropriate
the presence or absence of aforementioned surface coatings for use as a customized cell culture chamber/vessel due
demonstrates the capability to enhance osteogenesis in to its non-cytotoxic properties. However, MJF-printed
MC3T3e1 osteoblasts, which indicates surface coatings as a bioreactors exhibit varying ability in supporting different
potential regulator in osteoblast differentiation (Figure 6B). cell types and biological processes. Such disparities
Even though direct culture with the leachate medium between the MJF-printed substrate and polystyrene plate
indicated growth inhibition to some extent possibly due to could be attributed to the different responses of distinct
the interference from fusing and detailing agents, the ability cell types to possible influences b y s urface t opography
of osteoblasts to differentiate has not been compensated, as resulting from the microcavities and concave globular
suggested in Table 1. Taken together, while cells are able to microstructures on the uneven surface. Our study
grow, proliferate, and differentiate on MJF-printed PA-12, provides findings o n h ow w ell d ifferent ce ll ty pes gr ow
the substrate supports the long-term growth of certain cell on PA-12 printed by MJF technology, thus contributing
types better than the other. to the continuing development of PBF 3D printing
Microbial growth and fouling in 3D-printed PA-12 for biomedical application. Given the benefits o f M JF
reaction chamber emphasizes the fact that this material does technology and the outstanding properties of PA-12, we
not show any anti-fouling and antimicrobial capabilities. believe that this study has laid the groundwork for a more
Previously, studies that focus on the bacterial attachment comprehensive characterization in the future development
to polymer surfaces use E. coli as a model organism . of MJF-printed PA-12 to realize its eventual commercial
[73]
A closer look at the fluorescent images taken after 24 h of use in biological application.
incubation suggests that PA-12 surfaces are as effective as
polystyrene at retaining bacterial cells on the surface, as Acknowledgments
shown in Figure 8A. Majority of the cells remain viable None.
throughout the duration of the experiments. In accordance
with these findings, the MTT results further confirm Funding
the bacterial growth and viability from early bacterial This research was conducted in collaboration with HP
colonization of PA-12 surfaces (Figure 8B), a critical stage Inc. and supported/partially supported by the Singapore
during which cell-material interactions occur to yield
a sustainable population. These findings are consistent Government through the Industry Alignment Fund-
with the fact that a rough surface with R larger than the Industry Collaboration Projects Grant.
a
dimension of E. coli (~1 – 2 µm × 0.5 µm) retains bacteria Conflict of interest
on the surfaces, probably due to an increase in surface area
for adhesion . However, long-term investigations have The authors declare no conflicts of interest.
[74]
to be conducted to monitor the bacterial attachment and
possible biofilm fouling beyond the 24 h timepoint. Author contributions
Conceptualization: Yi Zhang
5. Conclusion Formal analysis: Balasankar Meera Priyadarshini, Wai Kay
MJF technology has shown exciting potentialities due to Kok
its design flexibility, faster overall production cycle than Funding acquisition: King Ho Holden Li, Yi Zhang
other 3D printing techniques, and strategy to minimize Investigation: Balasankar Meera Priyadarshini, Wai Kay
waste by employing recyclable and reusable powders. Kok, Vishwesh Dikshit, Shilun Feng
B
One potential application, where such benefits can be Writing – original draft: alasankar Meera Priyadarshini,
exploited, is in the fabrication of bioreactors. While Wai Kay Kok, Vishwesh Dikshit
3D printing has already found its way into bioreactor Writing – review & editing: Balasankar Meera Priyadarshini,
applications, the use of different processes and materials Wai Kay Kok, Vishwesh Dikshit, King Ho Holden Li,
in the novel MJF technology necessitates a thorough Yi Zhang

Volume 9 Issue 1 (2023) 31 https://doi.org/10.18063/ijb.v9i1.623