Dual Stimuli-Responsive Self-Assembled Supramolecular Nanoparticles

Supramolecular nanoparticles (SNPs) encompass multiple copies of different building blocks brought together by specific noncovalent interactions. The inherently multivalent nature of these systems allows control of their size as well as their assembly and disassembly, thus promising potential as biomedical delivery vehicles. Here, dual responsive SNPs have been based on the ternary host–guest complexation between cucurbit[8]uril (CB[8]), a methyl viologen (MV) polymer, and mono‐ and multivalent azobenzene (Azo) functionalized molecules. UV switching of the Azo groups led to fast disruption of the ternary complexes, but to a relatively slow disintegration of the SNPs. Alternating UV and Vis photoisomerization of the Azo groups led to fully reversible SNP disassembly and reassembly. SNPs were only formed with the Azo moieties in the trans and the MV units in the oxidized states, respectively, thus constituting a supramolecular AND logic gate. A guiding light: UV/Vis irradiation and chemical reduction have been used for the reversible disassembly/reassembly and irreversible disintegration, respectively, of responsive supramolecular nanoparticles stabilized by ternary host–guest complexes (see picture). The disassembly proceeds through an initial aggregation phase that is attributed to different response times of the multivalent core and the monovalent shell upon photoswitching.