The Electrostatic‐Mediated Formation of a Coordination Complex: the Trapping and Release of an Antitumor Drug with an Anthracycline Core from {Mo 72 Fe 30 }‐Based Ensembles

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This article studies the binding of the antitumor drug doxorubicin (DOX) with the nanocluster polyoxometalate (POM) {Mo 72 Fe 30 }, the latter serving as the drug carrier. The formation of a stoichiometric complex POM@(DOX) 12 was observed in aqueous media. Using the Stern‐Volmer technique, we found the binding constant and free Gibbs energy for this interaction. The produced complex POM@(DOX) 12 was examined with ultraviolet‐visible (UV‐Vis), fluorescence (steady state and life‐time), infrared (IR) and X‐ray photoelectron spectroscopy (XPS), which revealed the stoichiometry of complex and a key role of {Mo 3 Fe 3 } host pores on the POM surface to DOX binding. DOX's ability to intercalate into DNA after binding with the {Mo 72 Fe 30 } was investigated using a pH typical for blood (7.4). A pH‐dependent release of DOX from POM@(DOX) 12 was demonstrated (rate constant is 3.3×10 −4 s −1 ). Finally, we showed that the immobilization of doxorubicin on the POM's surface can reduce undesired side effects.