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International Journal of Bioprinting Droplets prepared by air-focused bioprinting

Figure 4. Preparation of crosslinked alginate hydrogel particles by AFMDP. (a) Schematics showing the crosslinking of alginate hydrogel by Ca divalent
2+
ions. Optical images of alginate hydrogel particles prepared by (b) different inner capillary diameters, (c) different air flow rates, and (d) different alginate
concentrations. Dependence of particle diameter on (e) inner capillary diameter, (f) air flow rate, and (g) alginate concentration. If not specified, the
alginate concentration was 2 wt%.
5 μm, as shown in Figure S3 (Supplementary File). In controlled release, and immune therapy, as shown in
addition, the diameter of hydrogel particles could be Figure 5a. CAR-T cells were effective for cancer therapy.
tuned by varying the inner nozzle diameter, air flow rate, However, it was generally hard to manipulate CAR-T cells,
and alginate concentration, as shown in Figure 4b–d, and thus, the encapsulation of CAR-T cells in hydrogel
respectively. Since the increase of inner nozzle diameter particles provided a good solution for easy manipulation
would result in the increase of surface tension, the particle and controlled therapy. In this study, CAR-T cell-
diameter increased from 142 to 200 μm as the inner nozzle
diameter increased from 50 to 200 μm, as shown in Figure laden hydrogel particles were prepared by AFMDP and
4e. In contrast, the increase of air flow rate would cause collected in a CaCl bath. After full crosslinking, they were
2
the increase of viscous force, and thus the particle diameter transferred to and cultured in DMEM culture medium
decreased from 217 to 145 μm as the air flow rate increased at 37°C. CAR-T cell-laden hydrogel particles could
from 100 to 400 mL/min, as shown in Figure 4f. When the maintain their spherical shape even after cell culture for
alginate concentration increased from 0.5 wt% to 2 wt%, 2 weeks, during which CAR-T cells grew denser and were
the particle diameter decreased from 147 to 108 μm, as predominantly alive, as revealed by the live/dead assay kit
shown in Figure 4g. (Figure 5b and c). After cell culture, CAR-T cells could be
To highlight the broad applications of AFMDP, CAR-T released by disassembling hydrogel particles using PBS, as
cells were laden in the hydrogel particles for cell culture, shown in Figure S4 (Supplementary File).

Volume 10 Issue 1 (2024) 402 https://doi.org/10.36922/ijb.1102