Page 74 - IJB-7-4

Bioink for Reconstruction of Rigid-living Systems
printed or molded objects). It was observed that the the structure was slightly deformed; however, as the
integration of these two components to the original ink solvent corresponds to a minimal portion compared to
composition affected the overall structural definition the rest of the constituents. For this reason, a fast image
of the printed objects (Figure 2). The contour plot processing test was done, arrowing 97.5% similarity
representation of the surface response graph can be between a 3D printed cylinder of 50 layers after
found as part of the supplementary material (Figures crosslinking and desiccation (Figure 2B). This analysis
S3 and S4). The original ink exhibited a structural is an innovative way to characterize printing fidelity.
definition between 0.92 and 0.94; however, it was found Nevertheless, more improvements in the technique
that the definition could be improved (SSIM >0.95) by could be made in further studies to get more accurate
the addition of 0.1 g/cm – 0.6 g/cm of hydroxyapatite results.
3
3
(Figure 2). On the other hand, the addition of calcium This ink was designed to a helpful a carrier for
carbonate resulted in a lower structural definition (Soil- biological cargo in different orders of magnitude,
structure interaction [SSI] <0.92). Nevertheless, it depending on the biological species of interest that could
was found that when adding both: calcium carbonate go from 50 mm (corroborated at Figure 7) until the
and hydroxyapatite, the structural definition from the printing resolution of the assembled 3D printing system
printed object could be preserved (SSIM >0.92), even that experimentally was 1 mm (Figure 3). In the scanning
with the presence of the calcium carbonate in ink, electron microscope images (Figure 3B), the binding
possible when simultaneously adding 0.1 g/cm – 0.2 g/ from the polymer can be an attachment from the calcium
3
cm of calcium carbonate and 0.1 g/cm – 0.6 g/cm carbonate and hydroxyapatite round crystals; GelMA
3
3
3
of hydroxyapatite (Figure 2). Similarly, the addition and gelatin offer the porous platform to get the crystals
of 0.8 g/cm of calcium carbonate and 0.2 g/cm – incrusted due to its long polymer chains at a molecular
3 g
3
0.6 g/cm of hydroxyapatite resulted in a high structure level [19-21] .
3
definition. It is essential to highlight that adding beyond FT-IR corroborated the two crosslinking behaviors
0.7 g/cm of hydroxyapatite in the presence of calcium from the ink (Figure 4A); one clear result from the ionic-
3
carbonate reduces the structure definition (SSI <0.875) crosslinking comes from the OH peak observed at 3300
of the printed object (Figure S3 and S4). Therefore, cm , that states the covalent bonding between hydroxyl
−1
the development of enhanced inks for under seawater groups in alginic acid polysaccharides. The photo-
printing without losing their printing definition can be crosslinked material and the exposure at room conditions
carried by adding these two components to the original are similar because the photoinitiation with a wavelength
ink according to the previously described maximization in the spectrum related to blue light can come from
conditions. regular exposure to light; therefore, crosslinking occurs
It is essential to clarify that due to the loss of at a lower rate. Evidence from this is the peaks from N-H
solvent derived from room temperature desiccation, and C-H at 2950 cm and 2990 cm . Finally, carbonate
−1
−1
A B

Figure 3. Morphological studies of a 3D dried printed grid. (A) Demonstration of the feasibility of printing at a resolution of approximately
1 mm, with the aid of a commercial extrusion-based bioprinter. (B) Scanning electron microscope (SEM) image of the same grid at the
microscale at different sizes. To see the morphology of the surface and the binding from the bioceramics crystals to the polymer.

70 International Journal of Bioprinting (2021)–Volume 7, Issue 4