Designed magnetic nanoparticles for ferroptosis: Release of iron ions from metal-organic frameworks modified with iron oxides

The unique chemical properties of the catalytic and biocompatible metal organic framework MIL88b allow for considering it as prooxidant agent. The authors hypothesize whether additional modification of the MIL88b with an additional iron source as Fe 3 O 4 nanoparticles can increase both pro-oxidant activity and provide magnetic properties contributing to target delivery. The prooxidant activity of the Fe 3 O 4 -MOF was studied using electron paramagnetic resonance spectroscopy and methylene blue degradation reactions in the presence of hydrogen peroxide. To understand the reaction mechanism, the authors studied the released iron ions, as well as the surface composition using the X-ray photoelectron spectroscopy method. The addition of iron oxide leads to a more prolonged release of iron ions and the production of hydroxyl radicals within 24 h. The native MIL88b demonstrates the highest Fenton reaction rate due to "sacrificial" behavior (despite lower concentration of iron ions in the composition and on the surface compared to the modified sample) and the blocking of the active centers of MIL88b by Fe 3 O 4 on the surface. • MIL-88b catalyzes the Fenton reaction with internal and surface iron ions. • Concentration of released ions exceeded the concentration of surface ions. • Fenton reaction with the participation of MOF free ions proceeds faster at pH 4.5. • Higher iron concentrations do not increase the rate of the Fenton reaction.