Page 77 - IJB-9-1

International Journal of Bioprinting Osteoconduction and scaffold directionality

pores were randomly distributed, directionality was double-filament configurations, hollow, core–shell, and
not addressed in that study. The directionality of bionic filaments . How such new developments will
[29]
vascularization is largely hypoxia-driven (low tissue influence scaffold-based bone tissue engineering will be
oxygen level), which promotes the sprouting of seen over the next decade.
endothelial cells toward the oxygen-deprived tissue [36,37] .
For three different microarchitectures with pores from 5. Conclusions
0.35 mm to 0.65 mm, blood vessel volume/total volume In conclusion, we showed that for filament-based
increased with the pore diameter [38] . In our library, wall microarchitectures, the directionality of filaments, which is a
distances of 0.40 mm and 0.50 mm yielded the highest guiding cue for osteoconduction, is a key factor for filament
degree of osteoconduction and bone regeneration distance of 0.83 mm and beyond. At a distance of 0.40 mm
irrespective of directionality of the filaments. One can and 0.50 mm, directionality of filaments imposes no major
assume that vascularization is no limiting factor for bone influence on osteoconductivity. The optimal distance of
regeneration in wide-open porous microarchitectures as filaments to support and guide osteoconductivity is between
tested in this study and even less so for rod distances 0.40 and 0.50 mm, given that multiple bone ingrowth fronts
of 0.83 mm or 1.25 mm as realized in FilG083 and will form in complex defect configurations.
FilG125 scaffolds, where we saw a significant decline
in bone formation compared to the smaller 0.40 mm Acknowledgments
and 0.50 mm filaments. That suggests that although
vascularization is certainly a prerequisite for bone The authors would like to thank Ana Perez for her
formation and osteoconduction, it is not the limiting assistance with histologies.
factor in wide-open porous microarchitectures.
The optimal pore diameter for osteoconduction was Funding
found for TCP-based scaffolds to be between 0.70 and This research was funded by the Swiss National Science
[13]
1.20 mm with bottlenecks between 0.50 and 0.70 mm Foundation, grant number: 310030_197128 to FEW
and optimal rod distance in orthogonal titanium lattice
[39]
microarchitectures to be 0.80 mm . Here, for TCP-based Conflict of interest
filament microarchitectures, optimal filament distance The authors declare no conflicts of interest.
for osteoconduction was between 0.40 and 0.83 mm for
the Fil-type configuration and between 0.40 and 0.50 Author contributions
mm for the FilG-type configuration. Irrespective of
the microarchitecture type, it appears that voids in any Conceptualization: Franz E. Weber
microarchitecture should span not more than 0.80 mm Methodology: Chafik Ghayor, Indranil Bhattacharya, Julien
to ensure high osteoconductivity and optimal guiding Guerrero, Franz E. Weber
of bone ingrowth. The diagonal of 0.80 mm squares Formal analysis: Chafik Ghayor, Indranil Bhattacharya,
measures 1.13 mm and comes close to the maximal pore Julien Guerrero, Franz E. Weber
size of osteoconductive pore-based microarchitectures of Investigation: Chafik Ghayor, Indranil Bhattacharya, Julien
1.20 mm [1,13] . Despite the high variability of these diverse Guerrero, Franz E. Weber
microarchitectures, based on pores, lattice or filaments, the Resources: Franz E. Weber
optimal dimension of the voids between material surfaces is Data curation: Chafik Ghayor, Indranil Bhattacharya,
in a range between 0.80 mm and 1.20 mm. Therefore, these Julien Guerrero, Franz E. Weber
numbers can be applied to other microarchitectures as well. Writing—original draft preparation: Franz E. Weber
Writing—review and editing: Chafik Ghayor, Indranil
In this study, we used a grid-like configuration of
Bhattacharya, Julien Guerrero, Franz E. Weber
filament microarchitectures based on square-shaped Visualization: Chafik Ghayor, Indranil Bhattacharya, Franz
filaments. One could suspect that square-shaped filaments E. Weber
enhance directionality, since they expose directional strait Supervision: Franz E. Weber
surfaces to the ingrowing bone. To study the effect of round Funding acquisition: Franz E. Weber
versus square-shape filaments, additional studies on this
subject are needed. Moreover, in this study, we only looked Ethics approval and consent to participate
at grid-like configurations but also other configuration
with wavelike or honeycomb patterns can be produced with The protocol was in line with the European Union
extrusion-based 3D printing techniques. Such variations Directive 2010/63/EU and accepted by the local authorities
change the mechanics and the in vitro outcomes , as do (065/2018).
[40]

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Volume 9 Issue 1 (2023)olume 9 Issue 1 (2023) 69 https://doi.org/10.18063/ijb.v9i1.626