Unveiling the nanotoxicological aspects of Se nanomaterials differing in size and morphology

Although the general concept of nanotechnology relies on exploitation of size-dependent properties of nanoscaled materials,the relation between the size/morphology of nanoparticles with their biological activity remains not well understood.Therefore,we aimed at investigating the biological activity of Se nanoparticles,one of the most promising candidates of nanomaterials for biomedicine,possessing the same crystal structure,but differing in morphology(nanorods vs.spherical particles)and aspect ratios(AR,11.5 vs.22.3 vs.1.0)in human cells and BALB/c mice.Herein,we report that in case of nanorod-shaped Se nanomaterials,AR is a critical factor describing their cytotoxicity and biocompatibility.However,spherical nanoparticles(AR 1.0)do not fit this statement and exhibit markedly higher cytotoxicity than lower-AR Se nanorods.Beside of cytotoxicity,we also show that morphology and size substantially affect the uptake and intracellular fate of Se nanomaterials.In line with in vitro data,in vivo i.v.administration of Se nanomaterials revealed the highest toxicity for higher-AR nanorods followed by spherical nanoparticles and lower-AR nanorods.Moreover,we revealed that Se nanomaterials are able to alter intracellular redox homeostasis,and affect the acidic intracellular vesicles and cytoskeletal architecture in a size-and morphology-dependent manner.Although the tested nanoparticles were produced from the similar sources,their behavior differs markedly,since each type is promising for several various application scenarios,and the presented testing protocol could serve as a concept standardizing the biological relevance of the size and morphology of the various types of nanomaterials and nanoparticles.

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Cerium dioxide was used for the first time as reactive sorbent for the degradation of the organophosphate pesticides para-thion methyl, chlorpyrifos, dichlofenthion, fenchlorphos, and prothiofos, as well as of some chemical warfare agents-nerve gases soman and O-ethyl S-[2-（diisopropylamino） ethyl] methylphosphonothioate （VX）. CeO2 specimens were prepared by calcination of basic cerous carbonate obtained by precipitation from an aqueous solution. The CeO2 samples containing certain amounts （1 wt.%-5 wt.%） of the neighboring lanthanides （La, Pr, Nd） were prepared in a similar way from pure lanthanide salts. It was shown that ceria accelerated markedly the decomposition of parathion methyl causing the cleavage of the P-O-aryl bond in the pesticide molecule. A similar reaction mechanism was proposed for the degradation of other organophosphate pesticides and nerve agents. The degradation times （reaction half-times） were in an order of minutes in the presence of CeO2, compared to hours or days under common environ-mental conditions. The reaction in suitable organic solvents allowed conversions of about 90%for parathion methyl loading of 20 mg pesticide/g CeO2 within 2 h with a reactant half-life in the order of 0.1 min. The key parameter governing the degradation efficiency of CeO2 was the temperature during calcination. At optimum calcination temperature （about 773.15 K）, the produced ceria retained a sufficiently high surface area, and attained an optimum degree of crystallinity （related to a number of crystal defects, and thus poten-tial reactive sites）. The presence of other lanthanides somewhat decreased the reaction rate, but this effect was not detrimental and permitted the possible use of chemically impure ceria as a reactive sorbent. A fast organophosphate degradation was demonstrated not only in non-polar solvents （such as heptane）, but also in polar aprotic solvents （acetonitrile, acetone） that are miscible with water. This opens new possibilities for designing more versatile decontamination strategies. The cleavage of phosphate ester bonds is of a great importance not only for the degradation of dangerous chemicals （chemical weapons, pesticides）, but also for interactions of ceria （es-pecially the nano-sized one） in biologically relevant systems.