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Arguchinskaya, et al.
3.5. 3D bioprinting support was well visualized. Certain defects in the design

Since extrusion-based bioprinting with mechanical of the scaffold occur due to the small scale and can be
material supply does not provide instant pressure relief eliminated by printing in full-size mode. For further
and subsequent sharp pressure increase in the syringes procedures, the object was placed in the cold buffer bath.
when the dispenser change takes place (in contrast to 3.6. Geometry verification
pneumatic dosing), the formation of each new layer
requires preliminary normalization of the parameter. For The geometry of the printed scaffold with the support was
these purposes, next to the main object, an additional verified using CT (Figure 6A). Since incubation buffer
element was printed (in Figure 5A and B on the left). and collagen (as well as gelatin) have almost the same
During its formation, the pressure in the syringe was density, the solution was removed before CT-verification.
increased and by the time the scaffold was printed, it Some geometry-related discrepancy with the input model
reached the required value. (also general for collagen and gelatin) was observed. The
The decrease in material retraction frequency during possible reasons for this were half-scale object printing,
non-printing motions (both with gelatin or collagen) was processes of material fluidity, and drying process during
minimized using a concentric filling pattern. Preliminary and after the printing (including the time before the CT-
material testing showed that 150% material output and scanning). In respect of the total volume, the printed
layer height at the level of 75% of nozzle diameter (386 object exceeded the input model by 10.4% (18.013 cm
3
μm in the case of 21G needles) were appropriate printing vs. 16.314 cm ). The printed object had the redundant
3
parameters for both materials. Filling density was set at volume at the level of 24.0 % (Figure 6C) and the missing
66% (corresponding to 99% filling for 150% material volume of 13.6% (Figure 6D). The conforming volume
output). (for the model and printed object, Figure 6B) was 86.4%.
The described approach was verified by printing a
cell-free scaffold of thyroid cartilage at 1:2 scales. The 3.7. Biocompatibility
printing was conducted by two dispensers containing
collagen, and gelatin. The complete scaffold is shown in High cell survival was observed on the 3rd day of
Figure 5B. The scaffold was printed twice to confirm the scaffold incubation (Figure 7A). There were 88.1 ±
quality of the support. The printed scaffold corresponds 5.3% of living cells according to the Live/Dead assay. In
to the given thyroid cartilage model on the whole. Gelatin 4 days (Figure 7B), cell viability increased up to 94.5
± 5.2%. The difference was significant, according to
A B Chi-square test. Thus, the used biomaterial provides the
necessary level of biocompatibility for cell survival and
proliferation.
4. Discussion

In the literature, there is a significant number of studies
on the restoration of cartilage using hydrogel-based
scaffolds. However, they are mainly related to objects
Figure 5. The thyroid cartilage scaffold with the support. (A) In the
beginning of biofabrication: The white component was collagen, up to 0.5 mm in height. There were few studies aimed
[18]
while the transparent component was gelatin. (B) Immediately at creating complete cartilage scaffolds [16,17] . Sun et al.
after the printing: On the left side, the additional printing element, fabricated scaffolds which could be applied for treating
required for normalization of pressure in a syringe after changing thyroid cartilage injuries using low-temperature
the dispenser at each new layer. deposition technology with hydroxyapatite and chitosan.

A B C D

Figure 6. Thyroid cartilage scaffold with the support. (A) The input model (marked in blue) and the printed object CT-reconstruction (red).
(B) The conforming volume (blue). (C) The redundant volume (green). (D) The missing volume (orange).

International Journal of Bioprinting (2021)–Volume 7, Issue 2 109