SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Synthesis

148

Silver nanoparticle (Ag NP)-loaded chitosan composites have numerous biomedical applications; however, fabricating uniform composite microparticles remains challenging. This paper presents a novel microfluidic approach for single-step and in situ synthesis of Ag NP-loaded chitosan microparticles. This proposed approach enables obtaining uniform and monodisperse Ag NP-loaded chitosan microparticles measuring several hundred micrometers. In addition, the diameter of the composites can be tuned by adjusting the flow on the microfluidic chip. The composite particles containing Ag NPs were characterized using UV-vis spectra and scanning electron microscopy-energy dispersive X-ray spectrometry data. The characteristic peaks of Ag NPs in the UV-vis spectra and the element mapping or pattern revealed the formation of nanosized silver particles. The results of antibacterial tests indicated that both chitosan and composite particles showed antibacterial ability, and Ag NPs could enhance the inhibition rate and exhibited dose-dependent antibacterial ability. Because of the properties of Ag NPs and chitosan, the synthesized composite microparticles can be used in several future potential applications, such as bactericidal agents for water disinfection, antipathogens, and surface plasma resonance enhancers.

Concepts: Synthesis, Composite material, Silver, In situ, Microfluidics, Composite video, Aramid, Kevlar

32

Antimicrobial drug release from biomaterials for orthopedic repair and dental restorations can prevent biofilm growth and caries formation. Carriers for drug incorporation would benefit from long-term drug storage, controlled release, and structural stability. Mesoporous silica, synthesized through a co-assembly of silica and surfactant template, is an ideal drug encapsulation scaffold that maintains structural integrity upon release. However, conventional loading of drug within meso-silica pores via concentration-gradient diffusion limits the overall payload, concentration uniformity, and drug release control. Herein we demonstrate the co-assembly of an antimicrobial drug (octenidine dihydrochloride, OCT), and silica, to form highly-loaded (35% wt.) OCT-silica nanocomposite spheres of 500 nm diameter. Drug release significantly outlasted conventional OCT-loaded mesoporous silica, closely fit Higuchi models of diffusive release, and was visualized via electron microscopy. Extension of this concept to the broad collection of self-assembling drugs grants biomedical community a powerful tool for synthesizing drug-loaded inorganic nanomaterials from the bottom-up.

Concepts: Microbiology, Drug, Synthesis, Lactic acid, Dental caries, Silicon compounds, Antimicrobial, Dental restoration

31

The study objective was to investigate and synthesize available evidence relating to the psychological health of Emergency Dispatch Centre (EDC) operatives, and to identify key stressors experienced by EDC operatives.

Concepts: Psychology, Chemical synthesis, Synthesis

30

Hierarchical zeolites are a class of microporous catalysts and adsorbents that also contain mesopores, which allow for fast transport of bulky molecules and thereby enable improved performance in petrochemical and biomass processing. We used repetitive branching during one-step hydrothermal crystal growth to synthesize a new hierarchical zeolite made of orthogonally connected microporous nanosheets. The nanosheets are 2 nanometers thick and contain a network of 0.5-nanometer micropores. The house-of-cards arrangement of the nanosheets creates a permanent network of 2- to 7-nanometer mesopores, which, along with the high external surface area and reduced micropore diffusion length, account for higher reaction rates for bulky molecules relative to those of other mesoporous and conventional MFI zeolites.

Concepts: Chemical reaction, Petroleum, Adsorption, Synthesis, Mesoporous material, Chemical kinetics, Chemical engineering, Zeolite

29

The ability to synthesize a diverse spectrum of one-dimensional (1D) nanocrystals presents an enticing prospect for exploring nanoscale size- and shape-dependent properties. Here we report a general strategy to craft a variety of plain nanorods, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors. These cylindrical unimolecular nanoreactors enable a high degree of control over the size, shape, architecture, surface chemistry, and properties of 1D nanocrystals. We demonstrate the synthesis of metallic, ferroelectric, upconversion, semiconducting, and thermoelectric 1D nanocrystals, among others, as well as combinations thereof.

Concepts: Physics, Molecule, Copolymer, Polymer chemistry, Dimension, Vector space, Space, Synthesis

28

Two-dimensional or ultrathin layered materials are attracting broad interest in both fundamental science and applications. While exfoliation can provide high quality single- and few-layer flakes with nm to µm size, the development of wafer-scale synthesis methods is important for realizing the full potential of ultrathin layered materials. Here we demonstrate the growth of high quality few-layer BN films with controlled thickness by magnetron sputtering of B in N2/Ar, a scalable process using only benign, non-toxic reagents. BN films up to two atomic layers are synthesized by reactive deposition at high substrate temperatures. Thicker monocrystalline BN films with arbitrary number of atomic layers are achieved in a two-step process comprising cycles of alternating room temperature deposition and annealing. Tunneling transport across these BN films shows pinhole-free insulating behavior on µm2 scales, demonstrating the realization of high quality ultrathin dielectrics.

Concepts: Nitrogen, Solid, Materials science, Synthesis, Thin film, Dielectric, OSI model, Boron nitride

28

The interrenal gland of anurans synthesizes the steroids aldosterone and corticosterone, but it is unknown whether these hormones are synthesized by the same cell type. In this work, we aim to elucidate whether there are different steroidogenic cell types and whether they have specific regionalization in the interrenal gland of the male toad Rhinella arenarum. We characterized all cell types using histological, immuhistochemical, and histochemical methods as well as transmission electron microscopy. Furthermore, we evaluated the organization of the cell types in the gland and anteroposterior variations in the synthesis of the steroids. We found evidence of five cell types: two morphologically different steroidogenic cells, type 1: polyhedral cells tightly attached to each other that have spherical euchromatic nuclei and type 2: retracted cells loosely attached to each other that have oval heterochromatic nuclei. Cell type 2 is mainly observed in the inner zone of the gland. In addition, we observed two types of chromaffin cells, called type 3 and 4 cells, randomly distributed throughout the interrenal gland, as well as type 5 cells, recognized as summer cells. Morphometric analyses of the cell types in the anterior and posterior zones of the interrenal showed that the ratio “area of type 2 cells/total interrenal area” is significantly lower in the posterior zone. In vitro incubations showed that the posterior portion of the gland produces significantly higher amounts of both corticosterone and aldosterone. Overall, our results suggest that the type 2 cells are less active to synthesize both aldosterone and corticosterone, compared to type 1 cells. Unlike most previous reports on the interrenal gland of anurans, in R. arenarum there is a zonation of the steroidogenic cell types, which implies that the organ is not anteroposterior or dorsoventrally homogeneous. © J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.

Concepts: Cell nucleus, Cell, Cell type, Chemical synthesis, Synthesis, Amphibian, Frog, Toad

28

Our earlier research has shown that N-phenyl-2,2-dichloroacetamide analogues had much higher anti-cancer activity than the lead compound sodium dichloroacetate (DCA). In this current study, a variety of N-arylphenyl-2,2-dichloroacetamide analogues were synthesized via Suzuki coupling reaction and their anti-cancer activity was evaluated. The results showed that N-terphenyl-2,2-dichloroacetamide analogues had satisfactory anti-cancer activity. Among them, N-(3,5-bis(benzo[d][1,3]dioxol-5-yl)phenyl)-2,2-dichloroacetamide (6k) had an IC(50) of 2.40μM against KB-3-1 cells, 1.04μM against H460 cells and 1.73μM against A549 cells.

Concepts: Chemical reaction, Chemical element, Heck reaction, Suzuki reaction, Coupling reaction, Synthesis, Dichloroacetic acid

28

A general and practical method to synthesize 2-substituted benzofurans and indoles is described. This method employs easily accessible N-tosylhydrazones and o-hydroxy or o-amino phenylacetylenes as substrates. The reaction proceeds through a CuBr-catalyzed coupling-allenylation-cyclization sequence under ligand-free conditions.

Concepts: Chemical reaction, Chemical synthesis, Synthesis, Tryptophan, Indole, Benzofuran, Bartoli indole synthesis, Benzofurans

28

A series of novel naphthalene attached bis-oxazines were synthesized and characterized. The bis-oxazines were studied by VT-NMR analysis to assess the possibility of conformational twist. The bis-oxazine prepared from (l)-methylvalinate show a helical conformational twist in the single crystal X-ray analysis. Three isomers of bis-oxazines were prepared from chiral α-methylbenzyl amines, the meso isomer showed small optical rotation probably indicating the helical conformational twist in the molecule.

Concepts: DNA, Optics, Stereochemistry, Assessment, Chirality, Synthesis, Isomer, Meso compound