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International Journal of Bioprinting 3D-printed hydrogel with antioxidant activity

Figure 3. Thermal properties of cellulose microfibrils and guar gum-based inks: (A) thermogravimetric patterns and (B) derivative thermogravimetric
patterns. Abbreviations: CMF, cellulose microfibril; gg, guar gum; w/, 100 mL of 1% (w/v) CMFs.

gum might indicates CMF exfoliation from the matrix over-deposition of ink on the printer bed. The addition
consequent to the electrostatic repulsion and solvation of of guar gum considerably improved the printability of
macromolecules. Considering guar gum is in relatively CMFs. For example, CMFs with either 3% or 5% guar
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high amounts, possessing a lot of hydroxyl groups, more gum had dimensions similar to the customized design.
guar gum was coated on the fiber surface with the increase This is probably because of an increase in electrostatic
in the concentration of the guar gum solution. That could and cohesive forces of molecules leading to improved self-
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negatively affect ink printability. 24 assembly of the inks. However, CMFs/guar gum (1%) was
5
unstable after printing, and CMFs/guar gum (7%) was
3.4. Thermal properties of CMFs/ not extrudable through the nozzle of the printer, likely
guar gum-based ink due to its high viscosity and consistency index, creating
Thermogravimetric patterns of CMFs/guar gum inks were high electrostatic repulsion. In the 3D cube model,
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investigated to evaluate their thermal stability, especially dimensional error which considers the differences in the
during operations such as heat sterilization that often width, length, and height of printed objects compared
precede certain biological applications. The prepared ink with those of the designed model was used as a criterion
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showed < 10% weight decrease with –0.1%/°C degradation for printability. The constructs using CMFs with 3%–5%
after the temperature was raised to approximately guar gum gave comparable dimensions in both width and
< 270°C (Figure 3). The derivative curves in the derivative length of the designed model, which had less than 10%
thermogravimetric pattern showed a slightly reduced error. For further experiments, CMFs/guar gum (5%) was
thermal resistance from 332°C to 293°C as guar gum selected as it showed the best fidelity of final products with
concentrations increased, because of higher thermal the designed model.
stability of CMFs compared to guar gum. Nevertheless,
addition of 5% guar gum resulted in the highest residual The printing parameters of using CMFs/guar gum
weight at elevated temperatures (>350°C), suggesting such as infill density (30%–60%), printing speed (1–
optimal cohesive and electrostatic interactions between 10 mm/s), nozzle diameter (0.4–1.5 mm), and layer height
two polymers. 5 (0.3–0.6 mm) were optimized (Figure 4; Table S2 in
Supplementary File). At 30% infill density, the dimensional
3.5. Printability of the CMFs/guar gum inks and error of the printed construct was approximately 30%
optimization of printing conditions compared with the designed shape. When the infill density
A preliminary study to determine the printability of the increased to 50%–60%, a product with approximately
prepared inks based on the designed 2D and 3D models 90% similarity to the designed model was obtained. The
is presented in Table S1 (Supplementary File). CMFs were low deviation is likely because of the proper alignment of
not properly printed, possibly because of its low yield deposited filaments, enhancing the compactness of the
stress (Table 1), making it unstable in the nozzle causing printed construct. 42

Volume 10 Issue 1 (2024) 249 https://doi.org/10.36922/ijb.0164