Determining the microenvironment and protonation state of quercetin encapsulated in pillar[5]arene-based...

This study reports the optical properties of quercetin encapsulated in self-assembled nanoparticles made from a dicarboxyl-bis-pillar[5]arene/CTAB supramolecular complex, and correlates these properties with the nanoparticle architecture and microenvironment. Experimental evidence indicates that quercetin, in both its neutral and mono-anionic form, is mostly located within the nanoparticle, trapped between the pillararenes. In contrast, only a small fraction of the mono-anionic form is found on the nanoparticle surface. Quercetin is stabilized through hydrogen bonding and hydrophobic interactions, which play a crucial role in protecting the flavonol from oxidation and degradation. This stabilization explains our recent findings on the efficacy of these nanoparticles in delivering and facilitating the cellular internalization of quercetin.