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International Journal of Bioprinting 3D bioprinting of in vitro cartilage tissue model

Figure 4. SOX9 (red) and cell nuclei stained with DAPI (blue) over days 7 and day 14 of culture in Alpha 1 and 3D pellet control cultures.

fully controllable and tunable environment with which we of crosslinking and an increase in compressive modulus .
[35]
can develop cartilage human tissue models. Synthetic self- The changes in viscosity observed when applying higher
assembling peptide hydrogels have previously been used to stresses could be due to the increase in crosslinking degree
culture animal chondrocyte-based tissue models . Their as time progresses when the rheological measurement is
[35]
potential for use as a bioink and also their application in performed. In the rheological assessments, since low shear
3D bioprinting remains unexplored. Existing models rely stresses have been applied before, the PeptiInk has had lesser
on tissue engineering techniques such as 2D cell seeding, time to crosslink. Further to characterizing its rheology, an
which can lead to heterogeneous and uncontrolled cell initial bioprinting assessment was performed to visually
deposition. Here, we embrace the advantages of 3D assess any differences in filament deposition when using
bioprinting, and we assess the material use in both 3D different nozzle sizes (22G, 25G, and 27G). No differences
bioprinting and production of human cartilage in vitro in terms of filament continuity were observed; therefore,
tissue models. the mid-size nozzle, 25G, was chosen. This choice allowed
for a higher filament resolution than the 22G nozzle, but a
Firstly, the rheology of the PeptiInk Alpha 1 was assessed lower shear stress was expected to be generated in smaller
with and without the addition of media. As expected, the sizes , such as the 27G nozzle. Visual assessment of
[36]
addition of medium made the hydrogel less viscous under 25G-printed structures was performed to narrow down the
low shear stress, enabling a better shear thinning behavior extrusion pressure window using a constant printing speed
for 3D printing. However, surprisingly, at higher shear of 10 mm/s. This initial screening pinpointed a pressure
stresses, the viscosity appeared to increase. Previous work range of 8–10 kPa, which demonstrated the continuous
had reported the slight increase in compressive modulus deposition of the printing filament avoiding the fusion
of this self-assembling peptide when mixed with culture of adjacent filaments. Further optimization was required
medium . The addition of cell culture medium is expected to understand the resolution of the bioink. The effect on
[35]
to change the pH of Alpha 1 and introduce higher amounts filament width of multiple printing speeds was assessed
of ions in the Alpha 1 (PeptiInk), promoting higher levels at a constant pressure within this range, and compared to

Volume 9 Issue 6 (2023) 459 https://doi.org/10.36922/ijb.0899