The current study evaluates the role of reactive oxygen species (ROS) in bioeffects of magnetite nanoparticles (MNPs), such as bare (Fe₃O₄), humic acids (Fe₃O₄-HA), and 3-aminopropyltriethoxysilane (Fe₃O₄-APTES) modified MNPs. Mössbauer spectroscopy was used to identify the local surrounding for Fe atom/ions and the depth of modification for MNPs. It was found that the Fe₃O₄-HA MNPs contain the smallest, whereas the Fe₃O₄-APTES MNPs contain the largest amount of Fe²⁺ ions. Bioluminescent cellular and enzymatic assays were applied to monitor the toxicity and anti-(pro-)oxidant activity of MNPs. The contents of ROS were determined by a chemiluminescence luminol assay evaluating the correlations with toxicity/anti-(pro-)oxidant coefficients. Toxic effects of modified MNPs were found at higher concentrations (>10⁻² g/L); they were related to ROS storage in bacterial suspensions. MNPs stimulated ROS production by the bacteria in a wide concentration range (10⁻¹⁵–1 g/L). Under the conditions of model oxidative stress and higher concentrations of MNPs (>10⁻⁴ g/L), the bacterial bioassay revealed prooxidant activity of all three MNP types, with corresponding decay of ROS content. Bioluminescence enzymatic assay did not show any sensitivity to MNPs, with negligible change in ROS content. The results clearly indicate that cell-membrane processes are responsible for the bioeffects and bacterial ROS generation, confirming the ferroptosis phenomenon based on iron-initiated cell-membrane lipid peroxidation.

The production of stable and homogeneous batches during nanoparticle fabrication is challenging. Surface charging, as a stability determinant, was estimated for 3-aminopropyltriethoxysilane (APTES) coated pre-formed magnetite nanoparticles (MNPs). An important consideration for preparing stable and homogenous MNPs colloidal systems is the dispersion stage of pre-formed samples, which makes it feasible to increase the MNP reactive binding sites, to enhance functionality. The results gave evidence that the samples that had undergone stirring had a higher loading capacity towards polyanions, in terms of filler content, compared to the sonicated ones. These later results were likely due to the harsh effects of sonication (extremely high temperature and pressure in the cavities formed at the interfaces), which induced the destruction of the MNPs.

This study presents an analysis of a set of iron oxides nanoparticles (NPs) (γ-Fe₂O₃, α-FeOOH, δ-FeOOH, 5Fe₂O₃·9H₂O, and Fe₃O₄) as potential candidates for ferroptosis therapy in terms of a phase state, magnetic characteristics, and the release of Fe^2+/Fe³⁺ as ROS mediators. Due to the values of saturation magnetization for Fe₃O₄ (31.6 emu/g) and γ-Fe₂O₃ (33.8 emu/g), as well as the surface area of these particles (130 and 123 m²/g), it is possible to consider them as promising magnetically controlled carriers that can function with various ligands. The evaluation of the release of Fe²⁺/Fe³⁺ ions as catalysts for the Fenton reaction showed that the concentration of the released ions increases within first 3 h after suspension and decreases within 24 h, which probably indicates desorption and adsorption of ions from/onto the surface of nanoparticles regardless their nature. The concentration of ions released by all nanoparticles, except α-FeOOH-Fe²⁺, reached 9.1 mg/L for Fe³⁺ to 1.7 mg/L for Fe²⁺, which makes them preferable for controlling the catalysis of the Fenton reaction. In contrast, a high concentration of iron ions to 90 mg/L for Fe³⁺ and 316 mg/L for Fe²⁺ released from compound α-FeOOH-Fe²⁺ allows us to utilize this oxide as an aid therapy agent. Results obtained on iron oxide nanoparticles will provide data for the most prospective candidates that are used in ferroptosis-inducing systems.

In this paper composites containing metal-organic framework MIL88b(Fe), nanoparticles magnetite (Fe3O4) or maghemite (γ-Fe2O3) modified by humic acids or ascorbic acid were synthesized and tested in the decomposition reaction of methylene blue. Analysis of predictive model based on multi-factor correlation analysis «physical-chemical properties — concentration of methylene blue after degradation» showed that in a line of selected parameters (initial iron concentration in sample, elemental cell parameter, Fe2+/Fe3+ ion ratio on sample surface, total iron ion released concentration, surface area specific, surface charge), a significant factor influencing Fenton reaction kinetics, is only the total concentration of the released iron ions (p-value = 0.0162). The influence of separate Fe2+ and Fe3+ ions and reaction time on the Fenton reaction kinetics was evaluated by multi-factor analysis. The results demonstrated that concentrations of released iron ions are statistically significant, with a square of the concentration of ions Fe2+ and the result of the reaction time to the concentration of ions Fe3+. A comparison of the sign and the coefficient values shows that an increase in ion concentration results in a reduction in methylene blue concentration, thereby accelerating the Fenton reaction rate, with Fe2+ ion concentration affecting more than Fe3+. The resulting model is proposed as a means of selecting a sample with the maximum Fenton reaction rate at a given point in time.