Triple composite based on metal-organic framework: differences in production of reactive oxygen species in biological and non-biological media.

A significant challenge in nanoscience is the unpredictable translation of activity of reactive oxygen species (ROS) from chemical to biological environments; this is the result of the complexity of biological regulatory mechanisms, antioxidant defenses, and interactions with cellular components (enzymes, membranes, etc.). The paper studies bioeffects of magnetically-controlled ROS-inducing compounds: triple composite Fe₃O₄-HA-MOF and its components (Fe₃O₄-MOF, HA, and MOF), where Fe₃O₄, HA, and MOF represent magnetite, humic acids, and metal-organic framework MIL-88B. ROS levels were evaluated in different media: non-biological (distilled water and 3%NaCl solution) and biological (bacterial cells Photobacterium phosphoreum and isolated bacterial enzymes). Luminol chemiluminescence method was used to assess ROS content. Variations of ROS content in non-biological media were revealed. Based on spectrophotometric and electrochemical analyses, the variations were explained by MOF degradation, iron ion release, and HA desorption. In biological systems, all compounds exhibited a unified effect: enzymes completely neutralized ROS deviations; bacteria stabilized ROS contents at ~ 50% excess level, likely due to their regulatory mechanisms. Similar living-cell-like effect was found for HA-containing compounds (HA and Fe₃O₄-HA-MOF) in non-biological media. The bacterial bioluminescence was used as a traditional cellular bioassay: it did not detect toxicity of all compounds under the experimental conditions. Our findings suggest that bioeffects of Fe₃O₄-MOF-based composites depend on the properties of the third component-modificator (HA or other). It was concluded that it is impossible to predict ROS activity in biological media based solely on the physicochemical analyses; simple cellular bioassays (similar to bioluminescence bacterial assay) are recommended for accurate predictions.