Dynamic Supramolecular Hydrogels Spanning an Unprecedented Range of Host–Guest Affinity

Cucurbit[7]uril (CB[7]) macrocycles exhibit a broad range of host–guest binding affinity. Attaching pendant CB[7] and complementary guests on 8-arm PEG macromers affords supramolecular hydrogels with cross-link affinity spanning more than 5 orders of magnitude (1.5 × 107 to 5.4 × 1012 M–1) without changing network topology. Cross-link affinity translates directly to bulk dynamic properties; hydrogels with high-affinity cross-linking behave like covalent gels with limited ability to relax or self-heal. Cross-link affinity furthermore dictates the release rate of encapsulated macromolecules, as well as cell infiltration and material clearance in vivo. This work thus informs a role for affinity in dictating supramolecular hydrogel properties by quantifying and isolating this feature over an unprecedented range.