Fig. 1.

Double network (DN) hydrogels consist of two independent polymer networks with controlled properties. (A) Schematic illustrating adamantane (Ad-HA, blue) and β-cyclodextrin (CD-HA, red) modified hyaluronic acid (HA) supramolecular assembly through guest–host (GH, purple) bond formation. Representative (B) frequency sweeps (1.0–100 Hz, 0.5% strain) and (C) strain sweeps (1.0 Hz, 1–500% strain, then recovery to 1% strain) of storage (G′, filled symbols) and loss (G″, empty symbols) moduli of GH hydrogels at concentrations of 3% (blue) and 5% (purple). (D) Schematic illustrating PEG-fibrinogen that contains natural protease cleavage and cell adhesion sites and is functionalized with acrylated poly(ethylene glycol) (PEG), through a reaction with PEG-diacrylate (PEG-DA). To form hydrogels, unreacted acrylate groups on PEG-fibrinogen and optional additional PEG-DA are polymerized with ultraviolet light in the presence of a photoinitiator (I2959). (E) Representative time sweep (1.0 Hz, 0.5% strain) of the crosslinking of PEG-fibrinogen hydrogels (8.5 mg mL⁻¹) with 2% PEG-DA. (F) Young’s moduli of PEG-fibrinogen (8.5 mg mL⁻¹) with varying concentrations of PEG-DA (mean ± SD, ***p ≤ 0.001, ns = no significant difference by one-way ANOVA with Bonferroni post hoc).