Selective knockout of gold active sites

It has long been known that defects on a gold surface play an important role in electrocatalysis, but the precise mechanism has always been unclear. This work indicates that the defect sites provide partially filled d-orbitals that stabilize freeradical intermediates. Strong evidence for this hypothesis is that the sites can be selectively knocked out by treatment with OH• radicals generated by Fenton's reagent. The knockout effect is demonstrated using oxygen reduction, hydrogen reduction, and the redox electrochemistry of hydroquinone

Antiviral effects of tannic-acid modified AgNPs require direct interaction.

<p>(A) Schematics and results for pre-treatment experiments. The results are expressed as % of HSV-2 infected control in 291.03C cells pre-treated with 2.5 µg/ml of tannic acid-modified 13 nm, 33 nm and 46 nm AgNPs or respective carriers for 2 h, then infected with HSV-2. (B) Schematics for post-treatment experiments. The results are expressed as percentage of viral inhibition in HSV-2 infected 291.03C cell cultures, in which complete medium containing 33 nm and 46 nm AgNPs (5 µg/ml) and 13 nm AgNPs (2.5 µg/ml) or respective carriers were added at the indicated time points for up to 24 h. The data are shown as means from three independent experiments ± SEM. * represents significant differences with p≤0.05.</p

Inactivation of HSV-2 infection by tannic acid modified AgNPs is dose and size related.

<p>(A) Schematics of dose response experiments. Viral inhibition (%) in 291.03C cells infected with HSV-2 pre-incubated for 1 h with 13 nm (B), 33 nm (C), 46 nm (D) AgNPs and unmodified 10–65 nm (E) AgNPs or respective carrier buffers at 0.5, 1, 2.5 and 5 µg/ml. At 24 h p.i. cells and supernatants were collected and titrated to determine PFU/ml in comparison to HSV-2 infected cultures. The data are expressed as means from three independent experiments ± SEM. * represents significant differences with p≤0.001.</p

Tannic-acid modified AgNPs reduce HSV-2 infection <i>in vivo</i>.

<p>(A) Schematics of <i>in vivo</i> experiments. C57BL/6 mice were infected with HSV-2 pre-incubated or not with 13, 33 and 46 nm AgNPs or corresponding carriers (5 µg/ml). (B) HSV-2 DNA titers (copies/µg DNA) in the whole vaginal tissues determined by real-time PCR at 48 h p.i. (N = 6). (C) Sizes of infected sites determined by immunohistochemistry of HSV-2 antigens. (D) Schematics of post-infection treatment at 3 and 18 h p.i. with 33 AgNPs or carrier buffer (3×100 µl at 5 µg/ml) (N = 5). (E) HSV-2 DNA titers (copies/µg DNA) in the whole vaginal tissues determined by real-time PCR at 48 h p.i. (N = 6). (F) Sizes of infected sites determined by immunohistochemistry of HSV-2 antigens (N = 5). The bars represent means from three independent experiments ± SEM. * represents significant differences with <i>p</i>≤0.05, while ** <i>p</i>≤0.001.</p

Cytotoxicity and anti-HSV-2 activity of tannic acid-modified 13, 33, 46 nm AgNPs, unmodified 10–65 nm AgNPs or corresponding carriers in 291.03C cells.^*

<p>* The values shown are means from three independent experiments with each treatment performed in triplicate.</p>†<p>Cytotoxic effects were evaluated by neutral red assay to determine the concentration of 50% cellular cytotoxicity (CC₅₀) of the tested compounds.</p>‡<p>Antiviral effects were evaluated by plaque assay to determine the effective concentration that achieved 50% inhibition (EC₅₀) against HSV-2 infection.</p>§<p>SI. selectivity index.</p><p>CC₅₀/EC₅₀.</p

Tannic-acid modified AgNPs regulate cytokine and chemokine production in a size-related manner.

<p>TNF-α (A), IFN-γ (B), IL-6 (C), IL-10 (D) and CCL2 (E) production in the vaginal lavages of uninfected or HSV-2 infected C57BL/6 mice at 48 h with the virus dose pre-incubated or not with 13, 33 and 46 nm AgNPs or corresponding carriers. (F) INF-γ, IL-10 and CCL-2 production in the vaginal lavages from mice treated at 3 and 18 h p.i. with 33 nm AgNPs or the corresponding carrier buffer (3×100 µl of 5 µg/ml). The bars represent means from 3 separate experiments ± SEM (N = 5). * represents significant differences with p≤0.05, ** p≤0.01. n.d. - not detected.</p

Tannic acid-modified AgNPs block HSV-2 attachment and penetration.

<p>(A) Schematics of attachment and penetration experiments. (B) Viral inhibition (%) for virus attachment and penetration experiments in 291.03C cell cultures with the use of 33 nm and 46 nm AgNPs (5 µg/ml) and 13 nm AgNPs (2.5 µg/ml) and corresponding carriers. At 24 h p.i. cells and supernatants were collected and titrated to determine PFU/ml in comparison to HSV-2 infected cultures. (C) SEM images in EDS mode of HSV-2 incubated with 13 nm, 33 nm and 46 nm AgNPs, white arrows indicate nanoparticles on the viron's surface. White bars indicate 100 nm. (D) Kinetics of AgNPs and HSV-2 interaction expressed as % of HSV-2 infected positive controls. HSV-2 aliquots were mixed with 2.5 µg/ml of 13, 33 or 46 nm AgNPs or corresponding carriers, incubated for indicated time points, then used to infect GMK-AH1 cells and determine PFU/ml in comparison to HSV-2 infected cultures. The data are shown as means from three independent experiments ± SEM. * represents significant differences with <i>p</i>≤0.05, while ** <i>p</i>≤0.001.</p

Transmission electron microscopy (TEM) images of silver nanoparticles and DLS histograms.

<p>(A) 13±5 (13) nm, (B) 33±7 (33) nm, (C) 46±9 (46) nm and (D) 10±1–65±10 nm AgNPs.</p