Silver-Assisted Thiolate Ligand Exchange Induced Photoluminescent Boost of Gold Nanoclusters for Selective Imaging of Intracellular Glutathione

Metal/ligand exchange is a common strategy for precise assembly of metal nanoclusters (NCs) in organic phases. However, such a case is still not well studied in the aqueous phase. In this work we have demonstrated the silver ions assisted ligand exchange on water-soluble <i>N</i>-acetylcysteine (NAC) stabilized Au NCs. Silver ions may trigger both silver–gold metal exchange and silver addition on Au NCs. Unlike those well-reported silver induced photoluminescent (PL) enhancements, the processes show little changes in PL intensity. The as-obtained AuNAC@Ag NC can further promote the ligand exchange between NAC and glutathione (GSH) and induce a maximum of a 20-fold increase in PL emission at 570 nm. The enhancement was proportional to the concentration of GSH, with a linear range of 0–0.5 mM. For other thiol compounds such as cysteine, NAC, and cysteamine, no significant PL changes were observed. Cytotoxicity evaluation shows that the AuNAC@Ag NCs are biocompatible. Thus, the intracellular GSH can be specially visualized by the formation of stable AuNAC@AgGSH NCs. These results may be helpful to reveal the underlying processes of metal/ligand exchange on NCs in aqueous environment and pave a new avenue for facile design and preparation of efficient imaging probe candidates

The antifungal metabolites obtained from the rhizospheric <i>Aspergillus</i> sp. YIM PH30001 against pathogenic fungi of <i>Panax notoginseng</i>

<div><p>Eight anthraquinones (<b>1–8</b>), three xanthones (<b>11–13</b>) and two phenols (<b>9–10</b>) were isolated from <i>Aspergillus</i> sp. associated with <i>Panax notoginseng</i>, and their structures were determined as ziganein-1-methyl ether (<b>1</b>), 8-<i>O</i>-methylchrysophanol <b>(2</b>), averythrin (<b>3</b>), averufin (<b>4</b>), 8-<i>O</i>-methyl averufin (<b>5</b>), versicolorin B (<b>6</b>), averantin (<b>7</b>), methyl-averantin (<b>8</b>), arugosin C (<b>9</b>), diorcinol (<b>10</b>), sterigmatocystin (<b>11</b>), demethylsterigmatocystin (<b>12</b>) and dihydrosterigmatocystin (<b>13</b>) by spectroscopic analyses. Compounds <b>1</b>, <b>2</b> and<b> 5</b> were the novel isolates from genus <i>Aspergillus</i>. Compounds <b>3</b>, <b>6</b> and<b> 7</b> exhibited antifungal activity against <i>Fusarium</i><i>solani</i>, pathogenic fungus of <i>P. notoginseng</i>, with minimum inhibitory concentrations (MICs) of 16<b>–</b>32 μg/mL, and compounds <b>1</b>, <b>3</b>, <b>4</b>, <b>7</b> and <b>9</b> showed antibacterial activity against <i>Bacillus</i><i>subtilis</i> with MICs of 64–128 μg/mL, 16–32 μg/mL, 8–16 μg/mL, 16–32 μg/mL and 64–128 μg/mL, respectively. The metabolites showed the potential value in the research of antifungal agents, especially in searching for a biocontrol of diseases of <i>P. notoginseng</i>. The preliminary structure–activity relationships have been discussed for some of the compounds.</p></div

A Highly Potent Antibacterial Agent Targeting Methicillin-Resistant Staphylococcus aureus Based on Cobalt Bis(1,2-Dicarbollide) Alkoxy Derivative

Methicillin-resistant Staphylococcus aureus (MRSA) is a notorious superbug that is potentially life-threatening. Among conventional antibiotics, vancomycin is a “gold standard” agent used to treat serious MRSA infections. Such therapy, however, is often ineffective because of the emergence of less-susceptible strains. Therefore, the exploration of new antimicrobial agents, especially nonantibiotic drugs, to cope with the growing threat of MRSA has become an urgent necessity. Herein, we have investigated the possibility to develop a metallacarborane antimicrobial agent, cobalt bis­(1,2-dicarbollide) alkoxy derivative (K121), and we have evaluated the relevant anti-MRSA behaviors. We demonstrated that K121 has a dose-dependent anti-MRSA activity with a low minimal inhibitory concentration of 8 μg/mL and a high selectivity over mammalian cells. In particular, a high bacteria-killing efficiency was observed with eradication of all MRSA cells within 30 min. In addition, K121 showed a high inhibition effect on the formation of bacterial biofilm. More importantly, unlike vancomycin, a repeated use of K121 would not induce drug resistance even after 20 passages of MRSA. The mechanistic study showed that K121 kills MRSA by inducing an increase in the reactive oxygen species (ROS) production and consequentially inducing irreversible damage to the cell wall/membrane, which ultimately leads to the death of MRSA. Our results suggested that K121 may be used as a promising nonantibiotic therapeutic agent against MRSA infections in future clinical practices

In Vivo Biosynthesized Zinc and Iron Oxide Nanoclusters for High Spatiotemporal Dual-Modality Bioimaging of Alzheimer’s Disease

Alzheimer’s disease is still incurable and neurodegenerative, and there is a lack of detection methods with high sensitivity and specificity. In this study, by taking different month old Alzheimer’s mice as models, we have explored the possibility of the target bioimaging of diseased sites through the initial injection of zinc gluconate solution into Alzheimer’s model mice post-tail vein and then the combination of another injection of ferrous chloride (FeCl₂) solution into the same Alzheimer’s model mice post-stomach. Our observations indicate that both zinc gluconate solution and FeCl₂ solution could cross the blood–brain barrier (BBB) to biosynthesize the fluorescent zinc oxide nanoclusters and magnetic iron oxide nanoclusters, respectively, in the lesion areas of the AD model mice, thus enabling high spatiotemporal dual-modality bioimaging (i.e., including fluorescence bioimaging (FL) and magnetic resonance imaging (MRI)) of Alzheimer’s disease for the first time. The result presents a novel promising strategy for the rapid and early diagnosis of Alzheimer’s disease