Figure 9.

Schematic illustration of Xu’s design of the enzyme-triggered formation of supramolecular hydrogels. This particular precursor consists of a self-assembly promoting motif, an enzyme-cleavable group, and a PTX drug molecule. After the enzymatic reaction, the PTX derivative can spontaneously assemble into nanofibers in water that eventually entangle into a self-supporting hydrogel. In the absence of enzyme (alkaline phosphatase, ALP), the pregelator solution exhibits no defined nanostructure (A and D). Upon addition of ALP, cleavage of the phosphate group triggers self-assembly (B and E), resulting in hydrogel formation (C and F). (Adapted from Ref. [209] with permission)