Hand-ground fullerene-nanodiamond composite for photosensitized water treatment and photodynamic cancer therapy.

The unique capability of fullerene (C60) to absorb light and generate reactive oxygen species (ROS) has been extensively studied for photosensitized water treatment and cancer therapy. Various material synthesis strategies have been proposed in parallel to overcome its intrinsic hydrophobicity and to enhance availability in water and physiological media. We present here a strikingly simple approach to make C60 available to these applications by hand-grinding dry C60 powder with nanodiamond (ND) using a mortar and pestle. The resulting ND-C60 composite was found to form a stable aqueous colloidal suspension and efficiently drive photosensitized production of ROS under visible light illumination. ND-C60 rapidly adsorbed and oxidized organic contaminants by photogenerated ROS. In the experiments for photodynamic cancer therapy, ND-C60 was internalized by cancer cells and induced cell apoptosis without noticeable toxicity. Treatment of tumor-bearing mice with ND-C60 and light irradiation resulted in tumor shrinkage and prolonged survival time.

Activation of Hydrogen Peroxide by a Titanium Oxide-Supported Iron Catalyst: Evidence for Surface Fe(IV) and Its Selectivity.

Iron immobilized on supports such as silica, alumina, titanium oxide, and zeolite can activate hydrogen peroxide (H2O2) into strong oxidants. However, the role of the support and the nature of the oxidants produced in this process remain elusive. This study investigated the activation of H2O2 by a TiO2-supported catalyst (FeTi-ox). Characterizing the catalyst surface in situ using X-ray absorption spectroscopy (XAS), together with X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR), revealed that the interaction between H2O2 and the TiO2 phase played a key role in the H2O2 activation. This interaction generated a stable peroxo-titania ≡Fe(III)-Ti-OOH complex, which reacted further with H2O to produce a surface oxidant, likely ≡Fe[IV] ═ O2+. The oxidant effectively degraded acetaminophen, even in the presence of chloride, bicarbonate, and organic matter. Unexpectedly, contaminant oxidation continued after the H2O2 in the solution was depleted, owing to the decomposition of ≡Fe(III)-Ti-OOH by water. In addition, the FeTi-ox catalyst effectively degraded acetaminophen over five testing cycles. Overall, new insights gained in this study may provide a basis for designing more effective catalysts for H2O2 activation.

Nickel-Nickel oxide nanocomposite as a magnetically separable persulfate activator for the nonradical oxidation of organic contaminants.

The nanocomposite of metallic nickel and nickel oxide (denoted as Ni-NiO), synthesized by a simple sol-gel method, was found to activate peroxydisulfate (PDS), resulting in the effective oxidation of phenolic compounds and selected pharmaceuticals. A nonradical mechanism was proposed to explain the activation of PDS by Ni-NiO, in which organic contaminants are believed to be oxidized through an electron abstraction pathway mediated by the reactive complexes formed between PDS and the Ni-NiO surface. This mechanism was supported by multiple lines of evidence including radical scavenger experiments, the oxidation products, linear sweep voltammetry, and electron paramagnetic resonance spectroscopy. The Ni-NiO/PDS system exhibited a PDS utilization efficiency (expressed by the ratio of degraded organic contaminant to decomposed PDS) that was over 80%, and Ni-NiO showed a greater activity for PDS activation than a commercial nanoparticulate nickel oxide. This improved performance of Ni‒NiO was attributed to the disproportioned incorporation of the metallic Ni into the NiO matrix, creating more sites with oxygen vacancy. Also owing to the metallic Ni, Ni-NiO possessed magnetic properties and therefore could be easily separated and reused.

Differential Microbicidal Effects of Bimetallic Iron-Copper Nanoparticles on Escherichia coli and MS2 Coliphage.

Bimetallic iron-copper nanoparticles (Fe/Cu-NPs) were synthesized by a single-pot surfactant-free method in aqueous solution [via the reduction of ferrous ion to zerovalent iron nanoparticles (Fe-NPs) and the subsequent copper-coating by metal ion exchange]. The produced Fe/Cu-NPs formed aggregates of spherical nanoparticles (approximately 30-70 nm) of Fe-Cu core-shell structures with 11 wt % copper content. The microbicidal effects of Fe/Cu-NPs were explored on Escherichia coli and MS2 coliphage, surrogates for bacterial and viral pathogens, respectively. Fe/Cu-NPs exhibited synergistically enhanced activity for the inactivation of E. coli and MS2, compared to single-metal nanoparticles (i.e., Fe-NPs and Cu-NPs). Various experiments (microbial inactivation tests under different conditions, fluorescence staining assays, experiments using ELISA and qRT-PCR, etc.) suggested that Fe/Cu-NPs inactivate E. coli and MS2 via dual microbicidal mechanisms. Two biocidal copper species [Cu(I) and Cu(III)] can be generated by different redox reactions of Fe/Cu-NPs. It is suggested that E. coli is strongly influenced by the cytotoxicity of Cu(I), while MS2 is inactivated mainly due to the oxidative damages of protein capsid and RNA by Cu(III).

Polyphosphate-enhanced production of reactive oxidants by nanoparticulate zero-valent iron and ferrous ion in the presence of oxygen: Yield and nature of oxidants.

The production of reactive oxidants from nanoparticulate zero-valent iron (nZVI) and ferrous ion (Fe(II)) in the presence of oxygen was greatly enhanced by the addition of tetrapolyphosphate (TPP) as an iron-chelating agent. Compared to other ligands, TPP exhibited superior activity in improving the oxidant yields. The nZVI/TPP/O2 and the Fe(II)/TPP/O2 systems showed similar oxidant yields with respect to the iron consumed, indicating that nZVI only serves as a source of Fe(II). The degradation efficacies of selected organic compounds were also similar in the two systems. It appeared that both hydroxyl radical (OH) and ferryl ion (Fe(IV)) are produced, and OH dominates at acidic pH. However, at pH > 6, little occurrence of hydroxylated oxidation products suggests that Fe(IV) is a dominant oxidant. The degradation rates of selected organic compounds by the Fe(II)/TPP/O2 system had two optimum points at pH 6 and 9, and these pH-dependent trends are likely attributed to the speciation of Fe(IV) with different reactivities.

Acute cardiovascular toxicity of sterilizers, PHMG, and PGH: severe inflammation in human cells and heart failure in zebrafish.

In 2011, dozens of children and pregnant women in Korea died by exposure to sterilizer for household humidifier, such as Oxy(®) and Cefu(®). Until now, however, it remains unknown how the sterilizer affect the human health to cause the acute deaths. To find its toxicity for organ, we investigated the putative toxicity of the sterilizer in the cardiovascular system. The sterilizers, polyhexamethylene guanidine phosphate (PHMG, Cefu(®)), and oligo-[2-(2-ethoxy)-ethoxyethyl)-guanidinium-chloride (PGH, Oxy(®)) were treated to human lipoproteins, macrophages, and dermal fibroblast cells. The PGH and PHMG at normal dosages caused severe atherogenic process in human macrophages, cytotoxic effect, and aging in human dermal cell. Zebrafish embryos, which were exposed to the sterilizer, showed early death with acute inflammation and attenuated developmental speed. All zebrafish exposed to the working concentration of PHMG (final 0.3 %) and PGH (final 10 mM) died within 70 min and displayed acute increases in serum triacylglycerol level and fatty liver induction. The dead zebrafish showed severe accumulation of fibrous collagen in the bulbous artery of the heart with elevation of reactive oxygen species. In conclusion, the sterilizers showed acute toxic effect in blood circulation system, causing by severe inflammation, atherogenesis, and aging, with embryo toxicity.