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International Journal of Bioprinting Development and characterization of AAMP for hydrogel bioink preparation

gum showed shear-thinning property, but the viscosity of of different mixing conditions. Figure 3A and C shows the
xanthan gum (Figure 2B) is much higher than that of sodium mixing results for the gel with and without the alginate/Ca
2+
alginate (Figure 2A). Therefore, we can conclude that the reaction, respectively, at varying stages of mixing cycles at
viscosity of the mixture also mainly attributes to xanthan a speed of 3000 rpm. In both cases, it was seen that better
gum solution. Moreover, we also performed a time-wise homogeneity was achieved with increased mixing cycles.
viscosity measurement after the two solutions were mixed. It The mixing reached visual homogeneity at 50 cycles. These
can be seen that the viscosity remained constant in 10 min, qualitative results were further confirmed by a quantitative
except the initial fluctuation. This is much longer than the analysis using colorimetry (Figure 3B and D). It was seen
mixing time, so we assume that no gelation-induced viscosity that the percent variance decreased for both R and B values
change happened during mixing. We also performed flow as mixing cycle number increased. The lighter color of the
2+
ramp study for alginate solution mixed with Ca and gels in Figure 3C is probably due to darker color of the initial
incubated it overnight for full crosslinking (Figure 2D). The solution.
result shows that after crosslinking, the viscosity of alginate We also sought to determine the effect of speed on
became much higher, and at 10 1/s shear rate the viscosity of achieving homogeneity. Hydrogel mixing under 3 different
alginate reached 25 Pa·s. This further confirms that during speeds was compared (Figure 3E). Gel without the
the AAMP mixing, viscosity did not change much due alginate/Ca reaction was used to more easily visualize
2+
to the crosslinking, while the initial change in Figure 2C the difference between the different speeds. The fastest
might be due to fluctuation as the equipment just started mixing used is 3000 rpm. With all three being mixed for
rotating. Figure 3 shows the colorimetric characterization 20 cycles, visually, it was observed that the faster mixing

A B

C D

E F

Figure 3. Characterization of hydrogel mixing. (A) Hydrogel with Ca /Alginate reaction mixed by the AAMP at 5, 10, 20, 30, and 50 mixing cycles.
2+
(B) Standard deviation/percent variance of red (R) and blue (B) values in the case of 5, 10, 20, 30, and 50 mixing cycles by the dual-syringe mixing device.
Values decrease with increased cycle number which demonstrates increased homogeneity with increased mixing. (C) Hydrogel without reaction mixed by
the AAMP at 5, 10, 20, 30, and 50 mixing cycles. (D) Percent variances of R and B values in the case of 5, 10, 20, 30, and 50 mix cycles by the dual-syringe
mixing device. Values decrease with increased cycle number, which demonstrates increased homogeneity with increased mixing. (E) Hydrogel without
reaction mixed by the AAMP that underwent 20 mixing cycles at 3000 rpm, 1500 pm, and 750 pm. (F) Percent variances of R and B values in the case
of 750, 1500, and 3000 rpm for 20 mixing cycles by the dual-syringe mixing device. Values decrease with increased cycle number, which demonstrates
increased homogeneity with increased mixing.

Volume 9 Issue 4 (2023) 403 https://doi.org/10.18063/ijb.705