Endong Yang

Silver nanoparticles-quercetin conjugation to siRNA against drug-resistant Bacillus subtilis for effective gene silencing: in vitro and in vivo.

Quercetin (Qe) exhibited extremely low water solubility, and thus, it was modified using silver nanoparticles (AgNPs). We fabricated AgNPs combined with Qe (AgNPs-Qe). The modification suggested that the synergistic properties of Qe enhanced the antibacterial activity of AgNPs. However, AgNPs-Qe exerted no effect on many kinds of drug-resistant bacteria, including Pseudomonas aeruginosa and Bacillus subtilis. RNA interference has considerable therapeutic potential because of its high specificity and potential capability to evade drug resistance. Therefore, we stabilized AgNPs-Qe with a layer of molecules (siRNA). The newly fabricated nanoparticles exerted improved effect on many kinds of bacteria, including the most prominent drug-resistant species B. subtilis. Agarose gel electrophoresis showed that the highest critical nitrogen-to-phosphorus (N/P) ratio occurred at a vector/siRNA with a w/w ratio of 7:1. Characterization experiment indicated that the diameter of siRNA/AgNPs-Qe was approximately 40 nm (40 ± 10 nm). Moreover, AgNPs-Qe were stabilized with a layer of siRNA that was approximately 10nm thick. Results of the in vitro study suggested that siRNA/AgNPs-Qe could destroy the cell wall and inhibit bacterial propagation. Meanwhile, the in vivo experiment on the animal bacteremia model, as well as the optical imaging of nude mice and their isolated organs, demonstrated that bacteria accumulated in the blood, heart, liver, spleen, lungs, and kidneys after the intravenous injection of B. subtilis. The bacteria in the blood and organs, as well as the inflamed cells in the tissues, gradually decreased after the mice received intravenous tail injection of siRNA/AgNPs-Qe for treatment. Both the in vitro and the in vivo studies exhibit that siRNA/AgNPs-Qe can be a potential nanoscale drug delivery system for B. subtilis targeting bacterimia.

Antibacterial activity of ruthenium(II) polypyridyl complex manipulated by membrane permeability and cell morphology.

This study investigates the antibacterial effects of the ruthenium(II) complex RuBP and the mechanism of RuBP action on bacteria. Results show that RuBP can inhibit the growth of Gram-positive bacteria, such as Staphylococcus aureus and Micrococcus tetragenus. Cellular uptake and laser confocal microscopic studies reveal the efficient uptake of RuBP by M. tetragenus cells. Scanning electron microscopic observations of the morphologies of M. tetragenus and S. aureus treated with RuBP further confirm that direct contact of both bacteria with RuBP can damage the cell membrane and membrane integrity, which may eventually induce growth inhibition and bacterial death. After RuBP treatment, the electrical conductivity of the bacterial suspensions increases. Spectroscopic studies and agarose gel electrophoresis indicate that intact DNA and RNA decrease or disappear in RuBP-treated bacterial cells, thus demonstrating that RuBP performs its antibacterial function by increasing the permeability of cell membranes. This study provides new insights for understanding the antibacterial actions of RuBP and designing metal complex antibiotics for other biomedical applications.

Anti-tumor activity and mechanism of apoptosis of A549 induced by ruthenium complex

Two new ruthenium (II) polypyridyl complexes [Ru(MeIm)4(pip)]2+ (1) and [Ru(MeIm)4(4-npip)]2+ (2) were synthesized under the guidance of computational studies (DFT). Their binding property to human telomeric G-quadruplex studied by UV–Vis absorption spectroscopy, the fluorescent resonance energy transfer (FRET) melting assay and circular dichroism (CD) spectroscopy for validating the theoretical prediction. Both of them were evaluated for their potential anti-proliferative activity against four human tumor cell lines. Complex 2 shows growth inhibition against all the cell lines tested, especially the human lung tumor cell (A549). The RTCA analysis not only validated the inhibition activity but also showed the ability of reducing A549 cells’ migration. DNA-flow cytometric analysis, mitochondrial membrane potential (ΔΨm) and the scavenger measurements of reactive oxygen species (ROS) analysis carried out to investigate the mechanism of cell growth inhibition and apoptosis-inducing effect of complex 2. The results demonstrated that complex 2 induces tumor cells apoptosis by acting on both mitochondrial homeostasis destruction and death receptor signaling pathways. And those suggested that complex 2 could be a candidate for further evaluation as a chemotherapeutic agent against human tumor.

Effect of solvents on forming poly(butyl-2-cyanoacrylate) encapsulated paeonol nanocapsules

Abstract The effect of ethanol or acetone, as oil phase solvents, upon the form of paeonol-loaded poly(butyl-2-cyanoacrylate) encapsulated nanocapsules (Pae@PNCs) by interfacial spontaneously polymerization were investigated. Pae@PNCs characterizations including morphology, radius distribution, polydispersity index (PDI), particle size, zeta potential, entrapment efficiency (EE%), drug loading (DL%) and in vitro paeonol release kinetics were evaluated. Results show that 100% acetone have a significant effect on forming nanocapsules, which showed the smaller size (168.3 ± 6.76 nm) under scanning electron microscopy (SEM) and one radius distribution by the particle size analyser. The data showed that using 100% acetone to prepare Pae@PNCs was leading to smaller particle size and lower polydispersity index (PDI), higher zeta potential, better EE (%) and perfect DL (%), which is linear decrease in radius (r2 = 0.939) and PDI (r2 = 0.974) and linear increase EE% (r2 = 0.9879) and DL% (r2 = 0.9892) with the acetone concentration (range 10–100% v/v). Paeonol encapsulated into and adhered on PNCs were confirmed by UV–Visible spectra (UV–Vis), Fourier transform infrared spectroscopy (FTIR) and Differential scanning calorimetry (DSC). Drug release behavior in vitro showed that 100% acetone as solvents on developing Pae@PNCs have greater advantages in controlling and prolonging paeonol release. Results demonstrated that solvents have a significant influence on forming Pae@PNCs.

C aulobacter rhizosphaerae sp. nov., a stalked bacterium isolated from rhizosphere soil

The Gram-reaction-negative, aerobic, white- to pale-yellow-coloured and rod-shaped bacterium with a single polar flagellum or a stalk, designated strain 7F14T, was isolated from rhizosphere soil of cultivated watermelon (Citrullus lanatus) collected from Hefei, China. Growth of strain 7F14T was observed at pH 6.0-9.0, 10-30 °C and in the presence of 0-1 % (w/v) NaCl. Cells were catalase-negative and oxidase-positive. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain 7F14T formed a phyletic lineage within the genus Caulobacter of the family Caulobacteraceae and showed the highest 16S rRNA gene sequence similarities to Caulobacter henricii ATCC 15253T (98.66 %), Caulobacter segnis ATCC 21756T (98.27 %), Caulobacter vibrioides CB51T (97.92 %) and Caulobacter flavus RHGG3T (97.44 %). The G+C content of the genomic DNA was 68.6 mol%. Strain 7F14T contained Q-10 as the sole ubiquinone and 11-methyl C18 : 1ω7c, C18 : 1ω7c, C16 : 0 and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH) as the major fatty acids. The polar lipids profile consisted of phosphatidylglycerol, an unknown phosphoglycolipid, five unknown glycolipids, an unknown phospholipid and three unknown lipids. DNA-DNA relatedness values to the most closely related type strains Caulobacter henricii DSM 4730T and Caulobacter segnis DSM 7131T were 26.0 and 19.7 %, respectively. Based on unique phenotypic traits, and phylogenetic, chemotaxonomic and DNA-DNA hybridization results, strain 7F14T should be classified as a representative of a novel species of the genus Caulobacter, for which the name Caulobacter rhizosphaerae sp. nov. is proposed. The type strain is 7F14T (=CGMCC 1.15915T=KCTC 52515T).

Massilia buxea sp. nov., isolated from a rock surface

A Gram-stain-negative, rod-shaped and motile bacterial strain, designated A9T, was isolated from the surface of rock collected from the shore of Nvshan lake in Mingguang, Anhui province, China. Phylogenetic analysis based on 16S rDNA sequence data showed that strain A9T was affiliated with the genus Massilia and showed the highest sequence similarities to Massilia plicata KCTC 12344T (98.8 %) and Massilia lurida CGMCC 1.10822T (97.9 %). The major fatty acids (>5 %) were summed feature 3 (C16 : 1ω7c and/or C15 : 0 iso 2-OH), C16 : 0 and C18 : 1ω7c. Strain A9T contained Q-8 as the predominant ubiquinone and diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and an unidentified aminophospholipid as the predominant polar lipids. The DNA G+C content was 69.9 mol%. Mean DNA-DNA relatedness values between strain A9T and its closest phylogenetic relatives, M. plicata KCTC 12344T and M. lurida CGMCC 1.10822T, were 38.8 % and 23.23 %, respectively. On the basis of the results obtained in this study, strain A9T is considered to represent a novel species of the genus Massilia, for which the name Massilia buxea sp. nov. is proposed. The type strain is A9T (=DSM 103547T=CGMCC 1.15931T=KCTC 52429T).

Mucilaginibacter rubeus sp. nov., isolated from rhizosphere soil

A Gram-stain-negative, aerobic, non-motile, rod-shaped and non-spore-forming bacterium, designated EF23T, was isolated from rhizosphere soil of watermelon. Growth of strain EF23T was observed at 10-37 °C, at pH 5.0-9.0 and in the presence of 0-0.5 % (w/v) NaCl. Strain EF23T contained menaquinone 7 (MK-7) as the major isoprenoid quinone, and summed feature 3 (C16:1ω7c and/or iso-C15 : 0 2-OH), iso-C15 : 0, C16 : 0 and iso-C17 : 0 3-OH as the major fatty acids. Phosphatidylethanolamine was identified as the major polar lipid. The genomic DNA G+C content of strain EF23T was 43.7 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain EF23T was most closely related to Mucilaginibacter gossypii Gh-67T (98.9 % similarity) and Mucilaginibacter gossypiicola Gh-48T (97.6 %). DNA-DNA relatedness values between strain EF23T and M. gossypii KCTC 22380T and M. gossypiicola KCTC 22379T were 31.6 and 53.7 %. On the basis of the evidence presented in this polyphasic taxonomic study, strain EF23T is considered to represent a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter rubeus sp. nov. is proposed. The type strain is EF23T (=CGMCC 1.15913T=KCTC 52516T).