It has been shown that 36 nm Nano-Se has lower toxicity than selenite or selenomethionine, but these forms of selenium (Se) all possess similar ability to increase selenoenzyme levels. The size of nanoparticles plays an important role in their biological activity: as expected, 5-200 nm Nano-Se can directly scavenge free radicals in vitro in a size-dependent fashion. However, in Se-deficient cells and Se-deficient mice, the size effect of Nano-Se on increasing selenoenzymes and liver Se disappears unexpectedly. We hypothesize that under conditions of Se deficiency, the avidity of Se uptake mechanisms may be increased to maintain the biosynthesis of selenoenzymes, which are fundamental for redox homeostasis. This increased avidity may override the potential advantage of small size Nano-Se seen under Se-replete conditions, thereby eliminating the size effect. Once selenoenzymes have been saturated, Se uptake mechanisms may downregulate; accordingly, the size effect of Nano-Se can then reappear. To test this hypothesis, Se-deficient mice were administered either 36 or 90 nm Nano-Se at supranutritional doses, in both a short-term model and a single-dose model. Under these conditions, Nano-Se showed a size effect on Se accumulation and glutathione S-transferase (GST) activity. A size effect of Nano-Se was found in 15 out of 18 total comparisons between sizes at the same dose and time in the two models. Furthermore, the magnitude of the size effect was more prominent on Se accumulation than on GST activity. GST is strictly regulated by transcriptional and translational mechanisms, so its increase in activity normally does not exceed 3-fold. In contrast, the homeostasis of Se accumulation is not as tightly controlled. In the present experiments, GST activity had reached or was approaching saturation, but liver Se was far below saturation. Therefore, our results strongly suggest that the saturation profile of the tested biomarker has an impact on the size effect of Nano-Se. Since both GST and small molecular weight selenocompounds accumulated in vivo are important intermediates for chemoprevention by Se, our results also suggest that Nano-Se should be most effective as a chemopreventive agent at smaller particle size.

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The novel blue-purple luminescent bridging ligand N,N,N′,N′-tetrakis(2-pyridyl)-2,6-pyridinediamine (L) has been synthesized. The coordination of this ligand with a series of Zn(II), Cd(II), and Hg(II) salts has been investigated. Seven new complexes (1-7) were obtained and characterized by elemental analyses and single-crystal X-ray analyses. In the compounds Zn 2 -LCl 4 (1), Hg 2 LCl 4 (5), Hg 2 LBr 4 (6), and Hg 2 LI 4 (7), each ligand is coordinated to two metal ions, forming dinuclear moieties, which are further connected via weak intermolecular M‚‚‚X interactions, affording one-dimensional chains. The complexes 4) forms a zigzag 1-D motif with two kinds of Cd-I-Cd bridges. Furthermore, the 1-D chains in all these complexes are connected by face-to-face π-π stacking interactions, affording 2-D networks with various structural geometries. All of these complexes are luminescent in the solid state, with the emission maxima varying in the visible light region within the range of 440-520 nm.

A core–shell fiber-constructed pH-responsive nanofibrous hydrogel membrane was fabricated for gravity-driven oil/water separation in acid, neutral, and alkali environments.