Oxidant-responsive ferrocene-based cyclodextrin complex coacervate core micelles

Coacervate-core micelles are considered promising materials for several applications, from catalysis to drug delivery. However, oxidant-responsive coacervate-core micelles, able to undergo structural changes upon specific oxidation stimuli, are not well reported. Here, we present a novel ferrocene–dipicolinic acid derivative as redox-responsive subcomponent to be incorporated in cyclodextrin-based coacervate core micelles, C4Ms, with tuneable core structure and responsiveness towards H₂O₂ treatment. The Fc-C4Ms are formed combining three orthogonal supramolecular interactions, namely (i) metal-to-ligand coordination between europium(III) ions and dipicolinic acid molecules, (ii) host-guest interaction between beta cyclodextrins and ferrocenes and (iii) electrostatic coacervation interaction. The micelle stability against oxidation can be controlled by varying three main parameters: (a) the core-unit structure, from monomeric metal complexes to supramolecular oligomers, (b) the H₂O₂ equivalents and c) the ratio between redox-responsive and non-redox-responsive bislinker. The H₂O₂-responsive ferrocene-based systems might have an interesting application, e.g. reactive oxygen species-mediated drug delivery.