Figure 1.

Overview of common approaches in designing stimuli-responsive host-guest systems. (A) Drug encapsulation is the most basic approach used in host-guest drug delivery applications. (B) The panel of drugs available for use in host-guest systems may be greatly expanded in the tethering of guest motifs to drugs of interest by labile bonds. (C) Porous nanoparticles have been used to encapsulate drugs, and these can be further equipped using host-guest chemistry to sterically block the release of cargo from the nanoparticle. Cargo is released as a specific stimuli shifts the host-guest binding away from the nanoparticle surface or displaces the macrocycle entirely. (D) Host motifs can also be incorporated into oligomeric or polymeric building blocks to enable the formation of material or hydrogel drug depots for the localized release of drug.