Here we report the electrochemical determination of the surface-area-to-volume ratio (SA/ V) of Au nanospheres (NSs) attached to electrode surfaces for size analysis. The SA is determined by electrochemically measuring the number of coulombs of charge passed during the reduction of surface AuO following Au NS oxidation in HClO, whereas V is determined by electrochemically measuring the coulombs of charge passed during the complete oxidative dissolution of all of the Au in the Au NSs in the presence of Br to form aqueous soluble AuBr. Assuming a spherical geometry and taking into account the total number of Au NSs on the electrode surface, the SA/ V is theoretically equal to 3/radius. A plot of the electrochemically measured SA/ V versus 1/radius for five different-sized Au NSs is linear with a slope of 1.8 instead of the expected value of 3. Following attachment of the Au NSs to the electrode and ozone treatment, the plot of SA/ V versus 1/radius is linear with a slope of 3.5, and the size based on electrochemistry matches very closely with those measured by scanning electron microscopy. We believe the ozone cleans the Au NS surface, allowing a more accurate measurement of the SA.

Here we describe the effect of aggregation on the oxidation of citrate-stabilized Au nanoparticles (NPs) attached electrostatically to amine-functionalized glass/ITO electrodes. When the Au NPs are attached to the electrode from a solution with pH greater than ∼3.0, they are well-separated on the electrode and oxidize in bromide-containing electrolyte at 0.698, 0.757, and 0.943 V (vs Ag/AgCl) for 4, 15, and 50 nm diameter Au NPs, respectively, in line with their size-dependent oxidation behavior. In solutions below pH 3.0, the Au NPs aggregate in solution and attach to the electrode in the aggregated form. The solution UV-vis spectra and scanning electron microscopy images of the electrodes show clear evidence of aggregation. The oxidation potential for aggregated 4 and 15 nm diameter Au NPs shifts positive by a maximum of 230 and 180 mV, respectively. The magnitude of the shift depends on the extent of aggregation, which was controlled by the solution pH and time. NP aggregation leads to a significant reduction in the surface area-to-volume ratio, which is likely responsible for the positive shift in the oxidation potential. The oxidation potential does not shift at all for aggregated 50 nm diameter Au NPs.

Mood disorder patients that are on long-term atypical antipsychotics treatment frequently experience metabolic dysfunctions. In addition to this, accumulating evidences points to increased risk of structural abnormalities, brain volume changes, altered neuroplasticity and behavioral depression with long-term antipsychotics use. However, there is paucity of preclinical evidences for long-term antipsychotic associated depression-like behavior. The objectives of the present study were: (1) to evaluate influence of long-term antipsychotic (olanzapine) treatment on rat behavior in forced swim test (FST) as a model for depression and; (2) to examine impact of glucagon-like peptide 1 (GLP-1) receptor agonist liraglutide - an antidiabetic medication for type II diabetes, on long-term olanzapine associated metabolic and behavioral changes in rats. Daily olanzapine treatment (0.5 mg/kg; p.o.) for 8-9 weeks significantly increased body weights, food and water intake, plasma cholesterol and triglycerides and immobility time in FST with parallel reduction in plasma HDL cholesterol levels. These results points to development of metabolic abnormalities and depression-like behavior with long-term olanzapine treatment. Acute liraglutide (50 μg/kg; i.p.) and imipramine (10 mg/kg, i. p.) treatment per se significantly decreased duration of immobility in FST compared to vehicle treated rats. Additionally, 3-week liraglutide treatment (50 μg/kg; i.p., daily) partially reversed metabolic abnormalities and depression-like behavior with long-term olanzapine-treatment in rats. None of these treatment regimens affected locomotor behavior of rats. In summary, add-on GLP-1 receptor agonists promise novel alternatives to counteract long-term antipsychotics associated behavioral and metabolic complications.

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Here we report that the peak oxidation potential (E p,ox ) of electrode-attached Au nanospheres (NSs) in anodic stripping voltammetry (ASV) experiments depends on the electrochemically measured surface area-to-volume ratio (SA/V). The SA/V in turn depends on the method of NS assembly onto the electrode, which results in different E p,ox values for the same-sized Au NSs that are assembled in different ways onto the same electrode material. The assembly methods tested on indium tin oxide-coated glass electrodes (glass/ITO) include electrostatic attachment to an amine-functionalized silane linker, electrophoretic deposition (EPD), direct drop-cast deposition, and drop-cast deposition after mixing with carbon black. The measured SA/V of same-sized NSs follows the order of silane linker > EPD > drop-cast with carbon black > direct drop-cast. The E p,ox decreases as the SA/V increases as controlled by the assembly method. The measured E p,ox for the Au NSs correlated to the measured SA/V better than the actual NS diameter. These findings reveal important information about what ultimately controls the oxidative stability of metal NSs and can help to explain previously described electrode effects on metal NS oxidation potentials. These results also provide guidelines for choosing an assembly method that optimizes the SA/V for performance and stability against oxidation or ripening (size increase).