Page 255 - IJB-10-1

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

Table 1. Rheological modeling of the inks
Model Parameter CMF w/1% gg w/3% gg w/5% gg w/7% gg
τ = τ + kγ˙ n τ (Pa) 4.74 ± 0.13 e 75.60 ± 2.28 d 194.59 ± 9.07 c 958.37 ± 22.49 b 1249.00 ± 8.49 a
0 o
k (Pa·s) 0.78 ± 0.04 e 110.18 ± 5.40 d 211.00 ± 9.90 c 186.27 ± 1.80 b 469.66 ± 3.31 a
N 0.11 ± 0.01 c 0.19 ± 0.03 b 0.19 ± 0.01 b 0.27 ± 0.01 a 0.14 ± 0.04b c
R (%) 81.09 86.61 95.54 97.13 88.04
2
G¢ = K¢(ω) ¢ n K¢ 44.49 ± 0.72 e 173.59 ± 4.82 d 272.59 ± 4.82 c 1062.42± 14.96 b 2529.05 ± 8.83 a
n¢ 0.024 ± 0.010 d 0.066 ± 0.002 b 0.069 ± 0.007 b 0.056 ± 0.003 c 0.085 ± 0.001 a
R (%) 92.29 94.05 95.89 94.09 93.53
2
G² = K²(ω) ² K² 11.40 ± 0.10 e 35.47 ± 1.44 d 251.59 ± 1.73 c 860.14 ± 4.40 b 1687.66 ± 9.29 a
n
n² 0.028 ± 0.014 b 0.042 ± 0.017 a 0.019 ± 0.006 c 0.003 ± 0.000 e 0.013 ± 0.001 d
R (%) 97.23 88.65 83.38 84.67 84.98
2
G* = A (w) 1/z A (Pa.s) 45.90 ± 0.20 e 176.85 ± 0.21 d 345.81 ± 6.43 c 1274.87 ± 3.68 b 2886.21 ± 7.11 a
F
F
z 41.32 ± 1.20 a 15.29 ± 0.62 d 16.42 ± 0.08 d 20.33 ± 1.88 c 25.19 ± 0.51 b
R (%) 93.60 94.05 96.44 95.12 94.49
2
Data are expressed as the mean ± standard deviation (n = 3).
The means indicated with different letters within the same row are significantly different at p < 0.05.
Abbreviations: gg, guar gum ; w/,100 mL of 1% CMFs
by the Herschel–Bulkley model (R = 81.09%–97.13%), higher storage energy as a result of increased exposure
2
varied significantly depending on the level of guar gum of hydrophobic groups to hydrogel matrix. Among the
35
in the matrix (Table 1). The τ of the hydrogel increased, hybrid hydrogels, the 5% guar gum had the lowest n’,
o
by 15.95–263.50 folds, with an increasing guar gum level, indicating that its elasticity had the least dependence on
indicating a variation in the stability of inks in the nozzle frequency, and implying its higher post-printing stability.
5
of the 3D printer before the application of force. Yield Besides, this ink has the least n’’ compared to CMFs and
34
stress is positively correlated with the potential energy other hybrid hydrogels, validating its good extrudability.
required to be overcome before flow can begin under The 7% guar gum had the highest n’ while the 1% guar gum
given shear stress; therefore, the moderately high yield had the highest n², suggesting poor printability and post-
5
stress of inks containing 3%–5% guar gum would ensure printing stability of the inks. These could be due to the
good extrudability owing to optimum shear-thinning volume exclusion effect of CMFs following its exfoliation
viscosity. The k increased, by 270.51 folds, following the because of the high guar gum level in the matrix, resulting
34
addition of 3% guar gum. A lower k was obtained using 5% in ink with poor ductility. 35
guar gum compared to 3% and 7% guar gum, likely due The weak gel model, R = 93.60%–96.44%, shows
2
to the variation in apparent viscosity of the inks. The n of that A of CMFs increased, by 3.85–62.88 folds, with
all the inks was < 1, which validated their shear-thinning increasing guar gum level, due to hydrophobic interactions
F
property. The n increased with increasing guar gum level of molecules and fibrillar crowding, resulting in high
24
in the matrix (up to 5%) probably because of increasing storage energy. CMFs had the highest z value, numbers of
35
inter-molecular networks, leading to improved self- interacting rheological units, likely due to the homogeneity
assembly of polymer chains with water molecules. The of its fiber. Lower z values of the hybrid hydrogels gave
7
36
high k and low n obtained for 7% guar gum were likely due a significantly higher A , due to increased interaction and
to the volume exclusion effect of CMFs that would make crosslinking of macromolecules, which suggests increasing
35
F
extrudability difficult, consistent with the poor injectability mechanical or gel strength as guar gum increased in the
of a high-concentration tragacanth acid hydrogel. 24
matrix. 13
The storage and loss moduli of the inks at different
angular frequencies varied (Figure 1A and B). K¢ and K² 3.3. Morphological and structural properties of
increased with an increasing level of guar gum, indicating CMFs/guar gum-based ink
increasing elasticity and viscosity of the inks, respectively. The morphological and structural properties of CMFs
35
A K¢ higher than the corresponding K² and a low loss incorporated with guar gums (1%–7%) were investigated
factor < 1 (Figure 1C), which are suggestive of viscoelastic (Figure 2), as good miscibility of polymers in the hydrogel
behavior, were obtained for all the inks, likely due to can help confer favorable post-printing stability on the

Volume 10 Issue 1 (2024) 247 https://doi.org/10.36922/ijb.0164