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. Author manuscript; available in PMC: 2021 Nov 1.
Published in final edited form as: Adv Biosyst. 2020 Sep 13;4(11):e2000129. doi: 10.1002/adbi.202000129

Figure 3.

Figure 3.

(A) Schematic of tetrazine-norbornene click reaction showing conjugated tetrazine and norbornene reactants and cycloaddition product. (B) Influence of Tz derivatization on the magnitude rate of photopolymerized 2.5 wt% PEG-based hydrogel stiffening in the presence of 1 wt% PEG-Tz, PEG-mTz, or PEG-Tz/mTz. (C) Effect of Tz substitution on Hep-Tz (0.5 wt%) stiffening of 3 wt% PEG-NB and 1 wt% PEG-SH hydrogels. Low, mid, and high Hep-Tz correspond to 1.4, 2.6, and 4 mM/wt%, respectively. (D) Effect of thiol-ene ratio on HA-Tz (0.5 wt%) of 3 wt% PEG-NB and PEG-SH hydrogels. (E) Stepwise stiffening of PEG-based hydrogels with PEG-Tz (0.5 wt%) incubation. Shaded regions indicate time period of stiffening (4 hours).