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Arguchinskaya, et al.
any study. In any case, both materials could be applied to similar density levels of collagen and surrounding media
the technique described in the study. (buffer) posed a problem to geometry verification. To verify
The used concentration of low-Bloom gelatin (12%) scaffold geometry, two options were possible. The first one
provided rapid “Sol-Gel” transition at room temperature. is related to the use of contrast agent whereas the other one
In case of higher Bloom value (e.g., 300 g Bloom) or required media (buffer) removal. Thus, in future studies,
lower temperature of the printing table, less concentrated the use of an additional high-density scaffold component
gelatin should be applied. In the present study, sterilization is required as it could distinguish the scaffold outline and
of gelatin was achieved by autoclaving. According to our thereby provide more accurate geometry verification.
data, this step does not significantly affect gelatin ability
of “Sol-Gel” transition. 5. Conclusion
The current stage in the development of bioprinting The proposed technique for bioprinting of tissue
is closely related to hydrogels. A number of biologically scaffolds with complex geometry using temporal support
inert synthetic polymers can be considered the heritage was verified. The approach is applicable in hydrogel-
of conventional 3D-printing. They have been used both based biofabrication using a two-dispenser bioprinter.
as a temporary supporting part [45] or a constant supporting This method is not limited for use with human thyroid
element of a scaffold [5,10,11] . However, since its extrusion cartilage; it can be applied to other types of cartilage as
temperature is much higher than the one appropriate for well as other tissue types.
cells and hydrogel (in gel state), the use of PLA, PVA
(both 180–200°C), and PCL (60–120°C) could not be Conflict of Interest
considered the first choice for bioprinting (in contrast to
other tissue engineering approaches). The exception is its No potential conflict of interest was reported by the
use for a base layer of a scaffold. authors.
The approach proposed in the study is based References
on the use of original model cross-sections. Unlike
other studies, the technique considers printing process 1. Ng WL, Chua CK, Shen YF, 2019, Print Me An Organ! Why
optimization, specifically, and printing time. The method We Are Not There Yet. Prog Polym Sci, 97:101145.
showed its applicability in the case of complex geometry. https://doi.org/10.1016/j.progpolymsci.2019.101145
Application of this approach requires validation of
printing parameters, such as nozzle diameter, filling 2. Lee JM, Ng WL, Yeong WY, 2019, Resolution and Shape
pattern, filling percentage, as well as retraction of related in Bio-Printing: Strategizing Towards Complex Tissue and
settings. It has been shown that creation of the support Organ Printing. Appl Phys Rev, 6:11307.
from a cross-section set with a rare slice step could https://doi.org/10.1063/1.5053909
reduce its quality, and an increase of the parameter leads 3. Engler AJ, Sen S, Sweeney HL, et al., 2006, Matrix Elasticity
to unreasonable complication of the model. Similarly, the Directs Stem Cell Lineage Specification. Cell, 126:677–89.
process of wall thickness modification should take into https://doi.org/10.1016/j.cell.2006.06.044
consideration should be well-balanced.
In the experiment, we found that printing duration was 4. Hadden WJ, Young JL, Holle AW, et al., 2017, Stem Cell
one of the main issues. The formation of the human thyroid Migration and Mechanotransduction on Linear Stiffness
cartilage scaffold in scale 1:2 took about 1.5 h to complete Gradient Hydrogels. Proc Natl Acad Sci, 114:5647–52.
(excluding preparatory procedures). Printing of the full- https://doi.org/10.1073/pnas.1618239114
sized scaffold would take over 5 h. To solve this problem, it 5. Ke D, Yi H, Est-Witte S, et al., 2019, Bioprinted Trachea
is advisable to use bigger needles (e.g., 18G vs. 21G needles Constructs With Patient-Matched Design, Mechanical and
used in the study). However, along with the acceleration of
the printing process (up to 2.5 h); It will irreversibly decrease Biological Properties. Biofabrication, 12:15022.
the scaffold quality. The issue of printing time is related https://doi.org/10.1088/1758-5090/ab5354
to another one related to CT-verification. The problem of 6. Ouyang L, Highley CB, Sun W, et al., 2017, A Generalizable
scaffold drying in the course of bioprinting arises in many Strategy for the 3D Bioprinting of Hydrogels from Non
current bioprinters models. Biofabrication of half- or full- Viscous Photo-Crosslinkable Inks. Adv Mater, 29: 1604983.
scale objects requires the possibility to control the chamber https://doi.org/10.1002/adma.201604983
humidity. Although the use of FRESH technique may be 7. Kim SH, Yeon YK, Lee JM, et al., 2018, Publisher Correction:
able to offer a solution, this approach has its own limitations
and is not applicable in many bioprinters. Precisely Printable and Biocompatible Silk Fibroin Bio-
Another challenge of the research was related to Ink for Digital Light Processing 3D Printing, Nat Commun,
geometry verification. In the course of CT-verification, the 9:2350.

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