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Coaxial nozzle-assisted electrohydrodynamic printing for microscale 3D cell-laden constructs

further verified that the printed alginate solution could nozzle-assisted electrohydrodynamic printing strategy
be instantly crosslinked to form hydrogel filament with could effectively fabricate the 3D cell-laden constructs
uniform dimension. Since the height of each layer was with high resolution, uniform cell distribution and high
close to the size of living cells, it might enable to print cell viability.
the filaments with single layer of cells in the vertical
direction for high-resolution cell printing. 4. Conclusion
Figure 6 shows the SME images of the elec tro hy- In summary, coaxial nozzle-assisted elec tro hy dro dy-
dro dynamically printed hydrogel construct with a nam ic printing technique was successfully developed to
layer number of 50. The printed filaments at neighbor fabricate microscale 3D cell-laden alginate constructs.
layers were tightly merged together, which maintained Process parameters such as applied voltage, alginate
structural integrity after freeze drying. The diameter feeding rate, stage moving speed and CaCl feeding rate
2
of the freeze-dried filaments was about 70 μm, slightly were systematically studied to stably print microscale
smaller than that of the freshly printed hydrogel filaments hydrogel filaments with 2D/3D organizations. 3D
due to shrinking during the freeze-drying process. hydrogel constructs with the maximum layer number of
Together, these results indicated that the introduction 73 can be electrohydrodynamically printed in a layer-
of coaxial nozzle in the electrohydrodynamic printing by-layer manner. The height of the printed constructs
process significantly enhance the capability to fabricate was approximately 1464.53 ± 14.46 μm and the filament
3D hydrogel constructs. dimension maintained relatively uniform (80 μm in
Cell-laden hydrogel constructs with a layer number width and 18.5 μm in height). Cell-laden constructs with
of 30 were finally electrohydrodynamically printed as uniform cell distribution and high cell viability (>90%)
shown in Figure 7A. Figure 7B shows fluorescent images was finally achieved. However, it is still challenging
of the cell-laden constructs (top view) stained with Live/ to fabricate higher complex heterogeneous 3D living
Dead assay. The cells were completely confined inside constructs with multiple cell types and hydrogel
the hydrogel filaments and most cells kept alive (green). compositions. In addition, the presented coaxial nozzle-
assisted electrohydrodynamic printing should be further
explored to solve these problems.
Conflict of Interest and Funding
No conflict of interest was reported by the authors. This
work was supported by the National Natural Science
Foundation of China (51422508, 51675412), Shaanxi
Key Research and Development Program (2017ZDXM-
GY-058) and the Fundamental Research Funds for the
Central Universities.
References

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Figure 6. SEM images of the electrohydrodynamically printed construct
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6 International Journal of Bioprinting (2018)–Volume 4, Issue 1