Cytotoxic and radical activities of metal-organic framework modified with iron oxide: Biological and physico-chemical...

Metal-organic framework (MOF) modified with iron oxide, Fe₃O₄-MOF, is a perspective drug delivery agent, enabling magnetic control and production of active hydroxyl radicals, •OH, via the Fenton reaction. This paper studies cytotoxic and radical activities of Fe-containing nanoparticles (NPs): Fe₃O₄-MOF and its components - bare Fe₃O₄ and MOF (MIL-88B). Luminous marine bacteria Photobacteriumphosphoreum were used as a model cellular system to monitor bioeffects of the NPs. Neither the NPs of Fe₃O₄-MOF nor MOF showed cytotoxic effects in a wide range of concentrations (<10 mg/L); while Fe₃O₄ was toxic at >3·10^-3 mg/L. The NPs of Fe₃O₄ did not affect the bacterial bioluminescence enzymatic system; their toxic effect was attributed to cellular membrane processes. The integral content of reactive oxygen species (ROS) was determined using a chemiluminescence luminol assay. Bacteria mitigated excess of ROS in water suspensions of Fe₃O₄-MOF and MOF, maintaining bioluminescence intensity closer to the control; this resulted in low toxicity of these NPs. We estimated the activity of •OH radicals in the NPs samples with physical and chemical methods - spin capture technology (using electron paramagnetic resonance spectroscopy) and methylene blue degradation. Physico-chemical interpretation of cellular responses is provided in terms of iron content, iron ions release and •OH radical production.