From Microenvironment Remediation to Novel Anti-Cancer Strategy: The Emergence of Zero Valent Iron Nanoparticles

Accumulated studies indicate that zero-valent iron (ZVI) nanoparticles demonstrate endogenous cancer-selective cytotoxicity, without any external electric field, lights, or energy, while sparing healthy non-cancerous cells in vitro and in vivo. The anti-cancer activity of ZVI-based nanoparticles was anti-proportional to the oxidative status of the materials, which indicates that the elemental iron is crucial for the observed cancer selectivity. In this thematic article, distinctive endogenous anti-cancer mechanisms of ZVI-related nanomaterials at the cellular and molecular levels are reviewed, including the related gene modulating profile in vitro and in vivo. From a material science perspective, the underlying mechanisms are also analyzed. In summary, ZVI-based nanomaterials demonstrated prominent potential in precision medicine to modulate both programmed cell death of cancer cells, as well as the tumor microenvironment. We believe that this will inspire advanced anti-cancer therapy in the future.

Sulfidation of Zero-valent Iron Nanoparticles for Environmental Remediation

<p>The ability of nano-sized zero-valent iron (nZVI) to remove environmental contaminants, from heavy metals to polyhalogenated hydrocarbons, has been well established. However, the reactivity of nZVI towards contaminants is hampered due to competing for side reactions with oxygen and water. Sulfidemodified nZVI (S-nZVI) has become a viable option as S-nZVI has been shown to reduce organic compounds such as trichloroethylene faster than nZVI while also maintaining an increased resistance to oxidation by water. The Fulton group has established that nZVI supported on a naturally occurring microsilicate (Microsilica600, or “misi”), from a Rotorua geothermal deposit, is capable of removing nitrates from water. This material, or nZVI@misi, minimises the potential bioaccumulation path that nZVI has, and is easier to handle than unsupported nZVI. This research investigated the effect of sulfidation of nZVI@misi (or S-nZVI@misi) on the reactivity towards the degradation of a variety of different potential contaminants. S-nZVI@misi was synthesised using sodium thiosulfate for sulfidation. Increasing the concentration of the reagent and sulfidation time from 3 hours to 24 hours resulted in high percentages of sulfur-to-iron (S/Fe) for each material. This increase in S/Fe had a significant impact on the removal of cadmium and chromium as with higher the percentage of S/Fe, the faster the removal of these species occurred. Compared to pristine nZVI@misi, S-nZVI@misi was significantly faster at removing both cadmium and chromium. However, sulfidation of nZVI@misi proved to reduce the rate of 4-nitrophenol reduction and prevent nitrate reduction from occurring. Experimental analysis also showed that cadmium removal was faster with S-nZVI supported by FeOOH-coated microsilica, compared to material supported by un-coated microsilica. Therefore, we have synthesised supported S-nZVI that quickly removes cadmium and chromium from solution compared to standard supported nZVI.</p>

Sulfidation of Zero-valent Iron Nanoparticles for Environmental Remediation

<p>The ability of nano-sized zero-valent iron (nZVI) to remove environmental contaminants, from heavy metals to polyhalogenated hydrocarbons, has been well established. However, the reactivity of nZVI towards contaminants is hampered due to competing for side reactions with oxygen and water. Sulfidemodified nZVI (S-nZVI) has become a viable option as S-nZVI has been shown to reduce organic compounds such as trichloroethylene faster than nZVI while also maintaining an increased resistance to oxidation by water. The Fulton group has established that nZVI supported on a naturally occurring microsilicate (Microsilica600, or “misi”), from a Rotorua geothermal deposit, is capable of removing nitrates from water. This material, or nZVI@misi, minimises the potential bioaccumulation path that nZVI has, and is easier to handle than unsupported nZVI. This research investigated the effect of sulfidation of nZVI@misi (or S-nZVI@misi) on the reactivity towards the degradation of a variety of different potential contaminants. S-nZVI@misi was synthesised using sodium thiosulfate for sulfidation. Increasing the concentration of the reagent and sulfidation time from 3 hours to 24 hours resulted in high percentages of sulfur-to-iron (S/Fe) for each material. This increase in S/Fe had a significant impact on the removal of cadmium and chromium as with higher the percentage of S/Fe, the faster the removal of these species occurred. Compared to pristine nZVI@misi, S-nZVI@misi was significantly faster at removing both cadmium and chromium. However, sulfidation of nZVI@misi proved to reduce the rate of 4-nitrophenol reduction and prevent nitrate reduction from occurring. Experimental analysis also showed that cadmium removal was faster with S-nZVI supported by FeOOH-coated microsilica, compared to material supported by un-coated microsilica. Therefore, we have synthesised supported S-nZVI that quickly removes cadmium and chromium from solution compared to standard supported nZVI.</p>

“Doing More with Less”: Ni(II)@ORMOSIL, a Novel Sol-Gel Pre-Catalyst for the Reduction of Nitrobenzene

Reduction of nitrobenzene with NaBH4 using zero-valent iron nanoparticles (ZVI-NPs) and NiCl2∙6H2O incorporated in organically modified hybrid silica matrices as ZVI@ORMOSIL and Ni(II)@ORMOSIL catalysts is proposed as a remediation strategy. Ni(II)@ORMOSIL is prepared by ion-exchanging H+ of the ORMOSIL matrix with NiII. Ni(II)@ORMOSIL is a pre-catalyst that undergoes reduction by NaBH4 by an in-situ reaction and promotes nitrobenzene reduction by the unconsumed NaBH4, leading to sparing use of the catalyst. Ni(II)@ORMOSIL undergoes color change from green to black in this process, returning to a green hue after washing and drying. Nitrobenzene reductions were examined in aqueous acetonitrile solvent mixtures, and the reduction cascade produced the reaction end-products with catalytic implications. Plausible mechanisms of ZVI@ORMOSIL and Ni(II)@ORMOSIL catalyzed reductions of nitrobenzene are discussed. This work is the first to report M(II)@ORMOSIL pre-catalysts for in-situ reduction of nitrobenzene, and expands the scope of the ORMOSIL series of catalysts for the reduction of polluting compounds. This approach enables the development of catalysts that use very low concentrations of transition metal cations.