Figure 2.
Gelation of alkyl-hydrazone and benzyl-hydrazone CANs. (a) Dynamic alkyl-hydrazone (green) crosslinks formed by reaction of alkyl-aldehyde (yellow) functionalized PEG with hydrazine (blue) functionalized PEG. (b) Stable benzyl-hydrazone (purple) crosslinks formed by the reaction of benzaldehyde (red) functionalized PEG with hydrazine (blue) functionalized PEG. (c) The final G∞ was statistically the same across all formulations. G∞ = [(G′)2 + (G′′)2](½) with plateau values (ΔG′/Δt ≈ ΔG′′/Δt ≈ 0) for each of the three hydrazone hydrogel conditions. (d) In situ gelation was monitored by a time sweep, showing shear storage (G’) and loss (G”) moduli over time. (e) Gelation points for hydrazone CANs were measured at ω = 1 rad s−1 and γ = 1%. Gelation point is defined here as the time required to measure a storage modulus greater than the loss modulus (G’ > G”), with an additional threshold of G’ ≥ 10 Pa to account for instrument error. Traces represent average measurements made in triplicate (n=3) with standard error where appropriate. Statistics represent the results of one-way ANOVA with Tukey’s multiple comparisons test (MCT) showing P ≥ 0.05 = ns, P < 0.05 = *, P < 0.01 = **, P < 0.001 = ***, P < 0.0001 = ****.