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Multifunctional 3D Printed Composite Hydrogel
higher than the G” values, indicating that the ink exhibited oscillatory strains were switched from minor strain (100 s
a “gel-like” behavior and stable mechanical properties. for each interval) to large strain (100%, 200%, or 300%,
The self-supporting ability could achieve high-fidelity 100 s for each interval), the G” was more significant than
printing of the scaffold . the G’, implying that the viscous behavior dominated
[39]
As shown in Figure 7G-I, at a low shear strain the hydrogel network . When the shear strain dropped
[40]
(1%) at 25°C, the G’ and G” remained almost unchanged, to 1%, the G’ quickly returned to its initial value, which
where the former value was greater than that of the latter. indicated that once the enormous strain was removed,
This indicated that the hydrogel network presented gel- the hydrogel realized the reconstruction of the network
like elastic properties under a minor strain. The amplitude structure due to the reformation of the hydrogen bonds.
This showed the recovery ability of the hydrogel after a
continuous large deformation. Figure 7I and Figure S2
indicate that the G’ of the TA-treated hydrogel gradually
increased and was higher than the untreated hydrogel.
Because TA provided reversible hydrogen bonds, the
movement of polymer chains in the T5 sample was
confined to relaxation at enormous strain. Therefore, T5
hydrogel exhibited a higher G’ values . The mechanical
[41]
and rheological analyses proved that TA improved the
mechanical properties.
3.6. Biocompatibility and osteochondral activity

The NAGA, NGL3, and T5 hydrogels showed good
biocompatibility (Figure 8). Compared with NAGA, the
addition of clay and GelMA increased cell proliferation.
It is worth noting that with the addition of TA, the cell
Figure 8. Cell proliferation of BMSCs cultured on NAGA, NGL3, proliferation on the T5 hydrogel increased significantly on
T5, and T10 hydrogels. the 7 day. The enhanced cell activity could be attributed
th
A

B C

Figure 9. (A) Alkaline phosphatase activity assay and calcium deposition assay. Osteogenic (B) and chondrogenic (C) gene expression of
BMSCs cultured on a NAGA, NGL3, T5, and T10 hydrogel (scale bar: 100 µm).

228 International Journal of Bioprinting (2022)–Volume 8, Issue 3