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Dual-Response Composite Hydrogels
A E F

H
B G

C
I J

D K L

M N O

Figure 2. Cellulose nanofibers (CN) orientation within 3D-printed CN + hyaluronic acid methacrylate (CN+HAMA) hydrogels. SEM
images of (A) CNs, (B) hyaluronic acid (HA), (C) HAMA, and (D) CN+HAMA hydrogels with different concentration ratios (The direction
of yellow arrows represent the alignment of the fibers). (E) Schematic diagram of the direct writing process of CN+HAMA hydrogels.
2D-WAXS patterns of CN+HAMA hydrogels before extrusion (F) and after extrusion (G) from the nozzle. (H) Normalized 2D-WAXS
azimuthal intensity distributions of the equatorial refection of CN+HAMA hydrogels before and after extrusion from the nozzle. Mueller
matrix microscopy images of CN+HAMA hydrogels (I and J) before and (K and L) after extrusion under cross-polarized light. (M) H NMR
1
spectrum of HA, HAMA. (N) The compressive stress–strain curves and (O) elastic moduli of various hydrogels. (*P < 0.05, **P < 0.01).
gelled due to self-association interactions between with photopolymerizable methacryloyl groups to allow
cellulose aggregation. Consequently, CN hydrogel UV secondary photo cross-linking during printing. Two
precursors performed temperature responsive property types of cross-linking processes were used to increase
and can be cross-linked by thermal gelation, which the stability of the structure. Mouser et al. added HAMA
helps to maintain structures during printing. However, to pHPMA-lac-PEG hydrogels to enhance printability
the printed structures with temperature-induced gelation and allow bioprinting with sufficient shape- stability of
were unstable. To address this issue, HA was modified hydrogels .
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130 International Journal of Bioprinting (2022)–Volume 8, Issue 3