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International Journal of Bioprinting Fine collagen scaffold for osteogenesis

and structural integrity of the scaffolds relied primarily on results, the expression of OCN and ALP was the highest
the intrinsic rheological properties of the hydrogel inks, in sample 2, indicating the highest level of osteogenic
including viscosity, viscoelasticity, and linear rheology. As differentiation of MSCs. The NCAD and HIF-1α expressions
discussed in Section 3.2., ink B demonstrated enhanced were also elevated in sample 2, reflecting a higher level of
linear rheological characteristics of ink B—presumably cell condensation and a more hypoxic condition. Lastly,
due to Schiff-base interaction—which contributed to its the expression of β-catenin, an osteogenic-related marker,
superior shape fidelity. was also most upregulated in sample 2 (Figure 13).
3.4. Mechanical study
Tensile testing was conducted on scaffolds from samples 4. Discussion
1–4, and the average elastic moduli were calculated 4.1. Ink rheological properties, printing quality, and
from the linear regions of the stress–strain curves post-treatments
(Figure 11). The moduli were 11.41 ± 0.18 MPa (sample Typically, the viscosity and rigidity of hydrogel inks,
1), 7.02 ± 1.35 MPa (sample 2), 6.99 ± 0.49 MPa (sample as measured through steady shear flow and oscillatory
3), and 4.75 ± 1.84 MPa (sample 4). The highest modulus rheological tests, are used to evaluate shape fidelity during
in sample 1 can be attributed to its smallest rod diameter printing. These are often conducted at a constant strain
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and pore size, which increased the number of crosslinking within the linear elastic region of the ink (0.5–1%). 36
junctions and improved resistance to deformation under When the hydrogel ink was printed at a relatively low
tensile stress.
speed, the induced strain remained within this linear
3.5. Cell study range, making such tests appropriate for measuring shape
On day 5, the OD value of sample 1 was lower than both fidelity. However, higher printing resolution often requires
samples 2 and 3 (Figure 12), which was presumably caused significantly higher speed, which can generate large
by its lower porosity. According to the western blot (WB) strains—sometimes exceeding 100%. Under such large
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Figure 10. DSC heat flow curve for ink A (cellulose/collagen I/alginate hydrogel) and B (oxidized cellulose/collagen I/alginate hydrogel). Abbreviation:
DSC: Differential scanning calorimetry.

Volume 11 Issue 4 (2025) 233 doi: 10.36922/IJB025140116