Long-lifetime aqueous Si-air batteries prepared by growing multi-dimensionally tunable ZIF-8 crystals on Si anodes.

Si-air batteries have a high energy density, high theoretical voltage, and long lifetime, but they present a low anode utilization rate in a potassium hydroxide electrolyte. In this work, a ZIF-8 protective layer was prepared and modulated by a secondary growth method and then applied to protect the Si flat and Si nanowire (NW) anodes of a Si-air battery. By adjusting the conversion ratio, particle size, and crystallinity of ZIF-8 on the Si surface, the contact mode of the Si anode with water and OH- was controlled, thus achieving long-term corrosion and passivation resistance. Si NWs@ZIF-8 exhibited the highest average discharge voltage of 1.16 V, and the Si flat@ZIF-8 anode achieved the longest discharge time of 420 h. This work confirms that ZIF-8 acts as an anode protective layer to improve the properties of Si-air batteries and also provides valuable insights into the protection of Si anodes by MOFs.

Effects of total saponins of Panax notoginseng on immature neuroblasts in the adult olfactory bulb following global cerebral ischemia/reperfusion.

The main active components extracted from Panax notoginseng are total saponins. They have been shown to inhibit platelet aggregation, increase cerebral blood flow, improve neurological behavior, decrease infarct volume and promote proliferation and differentiation of neural stem cells in the hippocampus and lateral ventricles. However, there is a lack of studies on whether total saponins of Panax notoginseng have potential benefits on immature neuroblasts in the olfactory bulb following ischemia and reperfusion. This study established a rat model of global cerebral ischemia and reperfusion using four-vessel occlusion. Rats were administered total saponins of Panax notoginseng at 75 mg/kg intraperitoneally 30 minutes after ischemia then once a day, for either 7 or 14 days. Total saponins of Panax notoginseng enhanced the number of doublecortin (DCX)(+) neural progenitor cells and increased co-localization of DCX with neuronal nuclei and phosphorylated cAMP response element-binding/DCX(+) neural progenitor cells in the olfactory bulb at 7 and 14 days post ischemia. These findings indicate that following global brain ischemia/reperfusion, total saponins of Panax notoginseng promote differentiation of DCX(+) cells expressing immature neuroblasts in the olfactory bulb and the underlying mechanism is related to the activation of the signaling pathway of cyclic adenosine monophosphate response element binding protein.

Effect of epigallocatechin-3-gallate on iron overload in mice with alcoholic liver disease.

Iron has long been related to the pathological process of alcoholic liver disease (ALD). Liver iron overload is known to accelerate the development of ALD. In the present study we aimed to examine the effect of epigallocatechin-3-gallate (EGCG) on iron overload of ALD and to explore the potential mechanisms involved in its protection against ALD in mice. Male C57BL/6J mice were given alcohol by intragastric administration for 12 weeks. At the end of 8th week, ALD mice were treated for 4 weeks for 10, 20 and 30 mg kg(-1) EGCG by intraperitoneal injection. Liver injuries were assessed by histopathologic examination and Serum Alanine Aminotransferase (ALT) levels. Serum iron content, hepatic iron concentration and liver malondialdehyde (MDA) contents were examined. In addition, hepcidin mRNA levels and transferrin (Tf) and transferrin receptor 1 (TfR1) protein levels of liver tissue were also evaluated. Compared with model group, treatment of ALD mice with EGCG ameliorated liver injuries, decreased serum iron level, hepatic iron levels and liver MDA contents, increased hepcidin mRNA level and decreased Tf and TfR1 protein expression in the liver. The results of our study explain a new point of view that the protective effect of EGCG on ALD is associated with its iron-chelating property. The possible mechanisms are that EGCG affects hepatic iron uptake and inhibits iron absorption in the small intestinal.

Tumor selectivity of stealth multi-functionalized superparamagnetic iron oxide nanoparticles.

Superparamagnetic iron oxide nanoparticles (SPIO-NPs) have traditionally been used as MRI contrast agent for disease imaging via passive targeting. However, there has been an increasing interest in the development of SPIO-NPs to cellular-specific targeting for imaging and drug delivery currently. The objective of our study was to develop a novel active tumor-targeting SPIO-NPs system by surface-modifying superparamagnetic iron oxide nanoparticles (SPIO-NPs) with o-carboxymethyl chitosans (OCMCS) and folic acid (FA) to improve their biocompatibility and ability to target specific tumor cells as well as to evade reticuloendothelial system (RES). The results in vitro indicated the covalent surface-modification of SPIO-NPs with OCMCS significantly reduced not only the nano-cytotoxicity but also the capture of SPIO-NPs by macrophage cells. On the other hand, the folic acid modification promoted the uptake of nanoparticles by FR-positive tumor cell lines, but had little impact on other cells without folate receptor (FR). MRI image and tumor histological analysis demonstrated the FA-OCMCS-SPIO-NPs had the ability to target tumor cells with FR in vivo. OCMCS and folic acid modification of SPIO-NPs could significantly improve both the SPIO-NPs biocompatibility and the FR target for MRI imaging, potential carrier for drug targeting and hyperthermia.

Pharmacokinetics and pharmacodynamics of subcutaneous injection and intravenous infusion of recombinant human interleukin-12 and recombinant human interleukin-12 combined with hepatitis B surface antigen in cynomolgus monkeys.

BACKGROUND/AIMS: Interleukin-12 (IL-12) is a cytokine that plays an important role in cell-mediated immunity and shows great potential as a therapeutic agent for the treatment of tumors and infectious diseases. METHODS: We investigated the pharmacokinetics (PK) and pharmacodynamics of recombinant human IL-12 (rhIL-12) and rhIL-12 combined with hepatitis B surface antigen (HB(s)Ag) after administration by subcutaneous (s.c.) injection or intravenous infusion in cynomolgus monkeys. RESULTS: After s.c. injection of rhIL-12 at doses of 0.15-1.5 microg/kg, the monkey's metabolism showed linear kinetic characteristics. The intramuscular injection of HB(s)Ag vaccine did not affect the pharmacokinetic profile of rhIL-12. In monkeys administered rhIL-12 in a continuous dosing fashion, serum rhIL-12 was undetectable, probably due to the neutralizing effect of anti-rhIL-12 antibodies. In monkeys receiving high-dose s.c. injection of rhIL-12, the T(max) for serum rhIL-12 concentration was 4-8 h, and the T(max) for serum interferon-gamma (IFN-gamma) concentration was 24-72 h. However, in monkeys receiving continuous dosing of rhIL-12, serum IFN-gamma concentration was very low or even undetectable. CONCLUSION: We found that the PK of rhIL-12 was dose-dependent and its pharmacological effects appeared after T(max) and lasted much longer than mean retention time.

Antidepressant effect of the extracts from Fructus Akebiae.

Fructus Akebiae is a common ingredient in many traditional Chinese medicine complex prescriptions for the treatment of mental disorders. Previous studies indicate that the main chemical compositions of Fructus Akebiae are triterpenoid saponins with hederagenin as their sapogenin. In the present study, we enriched hederagenin from the extracts of Fructus Akebiae with a purity of approximately 70%. Using behavioral tests sensitive to antidepressant drugs, we demonstrated that acute and sub-chronic administration of the extracts of Fructus Akebiae produced antidepressant-like effects, as evidenced by decreases in the duration of immobility in forced swim and tail suspension tests in mice and reversal of chronic unpredicted mild stress-induced inhibition of sucrose consumption in rats. In addition, the extracts decreased the levels of plasma adrenocorticotrophic hormone and serum corticosterone in rats exposed to chronic unpredicted mild stress. Both behavioral and biochemical effects of the extracts were mimicked by the proven antidepressant escitalopram. These results suggest that the extracts of Fructus Akebiae exert antidepressant activity. Administration of the extracts may be beneficial for patients with depressive disorders.

Conducting polymer memory devices based on dynamic doping.

Molecular electronic junctions consisting of a 20 nm thick layer of polypyrrole (PPy) and 10 nm of TiO2 between conducting layers of carbon and gold were investigated as potential nonvolatile memory devices. By making the polymer layer much thinner than conventional polymer electronic devices, it is possible to dynamically oxidize and reduce the polypyrrole layer by an applied bias. When the electrode in contact with the PPy is biased positive, oxidation of the PPy occurs to yield a conducting polaron state. The junctions exhibit a large increase in conductance in response to the positive bias, which is reversed by a subsequent negatively biased pulse. Switching between the conducting and nonconducting state can occur for pulses at least as short as 10 micros, and the conducting state persists after a positive bias pulse for at least 1 week. The read/write/read/erase cycle may be repeated for at least 1700 cycles, although with an error rate of approximately 3% due mainly to an incomplete "erase" step. The speed and retention of the PPy/TiO2 junctions are far superior to those of the analogous fluorene/TiO2 devices lacking the polymer, and the conductance changes are absent if SiO2 is substituted for TiO2. The observations are consistent with "dynamic doping" of the solid-state polymer layer, with the possible involvement of adventitious mobile ions. Although the speed of the current polymer/TiO2 junctions is slower than commercial dynamic random access memory, their retention is approximately 5 orders of magnitude longer.

Molecular electronics using diazonium-derived adlayers on carbon with Cu top contacts: critical analysis of metal oxides and filaments.

Evaporation of Cu metal onto thin (less than 5 nm) molecular layers bonded to conductive carbon substrates results in electronic junctions with an ensemble of molecules sandwiched between two conductors. The resulting devices have previously been characterized through analysis of current density-voltage (j-V) curves for several different molecular layers and as a function of layer thickness. The approach represents an 'ensemble' rather than 'single molecule' technique, in which the electronic response represents that of a large number of molecules (10(6)-10(12)) in parallel as well as the conducting contacts contained in the molecular junction. In this paper, we extend a more detailed investigation of two critical issues: the possibility of conduction by metal filaments, and the potential role of top contact oxidation contributing to the electronic properties of the junctions. The results show that the conductance of the junctions can be modulated by changes in the deposition environment, but that the changes are not related to Cu oxide in the top contact. Based on these results, we propose that the conditions during top contact deposition change the way in which the molecules contact the metal, leading to differences in the effective junction area. Finally, through systematic studies using variation of the temperature, we show that metal filament conduction is distinct from that observed for the molecular junctions and that if the current observed experimentally passed through nanoscopic metal filaments the Joule heating would lead to rapid melting. For a series of junctions with structurally related aromatic molecules (including biphenyl, nitrobiphenyl, fluorene, and nitroazobenzene), the electron transfer mechanism is briefly investigated using area-independent analysis methods. It is shown that field emission and/or transport through bands formed by the molecular layer is likely, based on the weak temperature dependence of junction conductance.

Electrochemical quartz crystal microbalance studies of the rectified quantized charging of gold nanoparticle multilayers.

Electrochemical quartz crystal microbalance (EQCM) was employed to investigate the dynamics of rectified quantized charging of gold nanoparticle multilayers by in situ monitoring of the interfacial mass changes in aqueous solutions with varied electrolytes. EQCM measurements showed that interfacial mass changes only occurred at potentials more positive than the potential of zero charge (PZC), where nanoparticle quantized charging was well-defined, whereas in the negative potential regime where only featureless voltammetric responses were observed, the QCM frequency remained virtually invariant. This was ascribed to the fact that nanoparticle quantized charging was induced by the formation of ion-pairs between hydrophobic electrolyte anions (PF6-, ClO4-, BF4-, and NO3-) and positively charged gold nanoparticles. Based on the total frequency changes and the number of electrolyte anions adsorbed onto the particle layers, the number of water molecules that were involved in the ion-pairing processes was then quantitatively estimated at varied particle charge states, which was found to increase with increasing hydrophobicity of the anions. Additionally, the electron-transfer dynamics of the gold particle multilayers were also evaluated by electrochemical impedance measurements. It was found that the particle electron-transfer rate was about an order of magnitude slower than that of the ion diffusion and binding.

Self-assembled multilayers of gold nanoparticles: nitrate-induced rectification of quantized capacitance charging and effects of alkaline (earth) ions in aqueous solutions.

Gold nanoparticle multilayers were self-assembled onto an electrode surface by using a dipping method. The particle assemblies exhibited quantized capacitance charging characteristics in aqueous media that were rectified by hydrophobic anions such as PF6-, BF4- and ClO4-, similar to the behavior with the monolayer counterparts. More interestingly, even in the presence of less hydrophobic anions such as NO3-, very well-defined single electron transfers were observed voltammetrically with these particle multilayers, a response unseen previously with particle monolayers. This was ascribed, in part, to the enhanced interactions between the particle multilayers and the electrolyte anions as well as the minimization of the structural defects within the particle thin films as compared to the monolayer counterparts. Further studies showed that with particles functionalized with oligo(ethylene oxide) moieties, the particle charge transfer properties were also found to be affected by electrolyte cations, reflected by the variation of the particle molecular capacitance and formal potentials with the nature of the alkaline (earth) metal ions.

Fullerene-functionalized gold nanoparticles: electrochemical and spectroscopic properties.

Fullerene (C(60))-tethered gold nanoparticles were synthesized by the coupling of the fullerene molecules with peripheral amine moieties on the particle surface. The particle composition was determined by thermogravimetric analysis and FT-IR spectroscopy. The resulting particles exhibited unique optical and electrochemical properties. UV-visible measurements showed that the C(60) characteristic absorption remained practically invariant whereas the fluorescence demonstrated rather drastic enhancement of emission efficiency as compared to the behaviors of C(60) monomers. Tethering of C(60) on the particle surface has virtually no effect on the particle molecular capacitance when C(60) is in neutral state, whereas when C60 is electroreduced, the particle effective capacitance increases drastically, reflected in the quantized capacitance charging measurements. The strong affinity of C(60) to amine moieties was also exploited to assemble multilayers of C(60) and gold particle nanocomposite structures. Quartz crystal microbalance measurements showed quite efficient adsorption of C(60) and particles up to two repeated cycles. However, the voltammetric responses of the surface-confined C(60) and gold particle composite structures were found to be complicated by the inaccessibility of electrolyte counterions due to the compact nature of the surface assemblies.

Ligand effects on the electrochemical and spectroscopic behaviors of methano[60]fullerene derivatives.

Effects of the ligand chemical structures on the electronic energy properties of two methano[60]fullerene derivatives were investigated voltammetrically and spectroscopically.