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International Journal of Bioprinting Oozing 3D-printed scaffolds for tissue engineering

variables like temperature and relative humidity of the Polylactic acid is a well-known biocompatible polymer
ambience have been reported to reduce fiber geometrical extensively used in biomedical applications. However, it
variability. Despite these considerations, a certain degree has certain limitations concerning its use such as a slow
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of heterogeneity can be expected when working with the degradation rate and strong hydrophobicity that can
oozing technique. 51 interfere with cell adhesion. 56,60 Alternatively, our results
Our results showed that the scaffolds of the oozing demonstrated that the NaOH treatment can increase the
groups exhibited an enhanced cell attachment and hydrophilicity characteristics of the PLA scaffold and
proliferation within 7 days of culture in comparison maintain them nearly 9 days, enhancing the potential of PLA
with controls. These results are possibly attributed to in bioengineering tissue applications. Furthermore, our
the microscale of the fibers together with an increased data demonstrated that control specimens showed a similar
porosity of the whole construct, as suggested elsewhere. 42,73 behavior to NaOH-treated specimens, suggesting that FDM
These data increase the knowledge about the utility of printing itself (melting and extruding process) modifies
FDM oozing-created constructs as scaffolds for growing PLA’s hydrophilic superficial properties. This temporally
cells, in concordance with other previous publications. increased hydrophilicity proposes a certain reversibility
Nevertheless, further culture assays should be performed to of the process when PLA is 3D-printed, corroborating
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confirm and improve the understanding of their biological other published studies. Interestingly, NaOH treatment
potential as a tissue-engineering strategy. 57 of the constructs did not affect their mechanical behavior,
probably due to the treatment only affecting the surface of
Regarding fiber geometry, we found that oozing groups the scaffolds, as previously described. 57
possessed dispersed fiber thickness depending on the
point they were measured, with the lowest measurement With good cell adhesion and proliferation activity on
found in the middle of the fiber in every case, in agreement the scaffolds in all tested specimens, our data support the
with other studies. In contrast, controls (Gy and Gof) application of this new set of scaffolds in tissue engineering.
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presented notably more homogeneous fiber thickness, In addition, in the cases of Oc and Os specimens, the cell
due to the fact that their infill cannot be considered a activity observed was higher than in the other specimens.
proper fiber but a regular FDM deposition. Oozing These results may be justified by the smaller fiber
5,54
groups exhibited statistically significant thinner fibers than separation in these two specimens in comparison with
controls, corroborating that the oozing effect can achieve Or and controls (Gof and Gy) that could allow increased
considerably narrower fibers than standard FDM printing cell density in the scaffold pores. This cell density could
as it has been proven in the literature. 44,51 Acquiring a better promote greater cellular proliferation and occupancy in
control over the range of thicknesses for every printed fiber these constructs, as it has been noted in other reports. 67,76
with the oozing technique would represent a major advance Nevertheless, these results may be confirmed with ulterior
for creating tissues with different fiber arrangements. studies in the field.
Printing speed together with flow rate and feed rate are
fundamental variables to be mastered in future works as 5. Conclusion
pointed elsewhere. 41,45,73 The oozing technique together with our AAD-controlled
As observed, a scaffold’s porosity grade was directly random distribution provides an interesting platform
related to mechanical behavior as an increase in the inner to create 3D-printed scaffolds with fibers in the range
voids led to a lower compressive strength. These results of microns that may better mimic the ECM niche than
are in agreement with other reported publications, which those fabricated by conventional FDM without advanced
described the scaffold porosity being inversely proportional programming. The benefits of this technical approach
to mechanical strength, resulting in a less dense construct are reliant on its capacity to overcome the limitation
that can only withstand lower stress. 56,74 Interestingly, it of the extruded filament’s diameter, and the typical
has been described that mechanical strength is geometry- parallel-like distribution of the scaffolds. Nonetheless,
dependent. Fernandez-Vicente et al. described a we are cognizant of the necessity to better control the
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series of constructs with different infill patterns and the oozing process to improve the mastering of the thickness
same mass that showed different mechanical behavior and geometry of fibers. Our strategy to combine AAD
as certain specimens supported greater mechanical with an accessible 3D printer together with cell culture
loading depending on their pattern design. Despite these assays represents a powerful approach to creating novel
observations, the influence of the geometry pattern caused biomimetic constructs with great potential suitable for
a variation of less than 5%. tissue engineering.

Volume 10 Issue 2 (2024) 513 doi: 10.36922/ijb.2337