Microspheres and microcapsules, a survey of manufacturing techniques: Part III: Solvent evaporation

A methodological survey of microsphere formation and microencapsulation techniques based on solvent extraction/evaporation techniques is presented. Thus, basic features of solvent extraction and solvent evaporation processes, including droplet formation, droplet/particle stabilization, and solvent removal, are outlined. Preparation of a wide range of microspherical and microcapsular products based on biodegradable polyesters, polysaccharides, and nonbiodegradable polymers are discussed. Dependence of microcapsule characteristics on manufacturing parameters, as well as performance evaluation of microspherical and microcapsular products, are also briefly covered.

生物土壤结皮的生态功能

Biological soil crust exists in desertification-prone areas.This paper focuses on ecological function of biological soil crust,including water relations,soil stabilization,carbon and nitrogen fixation,albedo and effects on vascular plants.Some preliminary suggestions are given for further understanding the relationship between biological soil crust and revegetation of degraded ecosystem in desertification-prone areas in Northwestern China.

Chiral metallo-supramolecular complexes selectively recognize human telomeric G-quadruplex DNA

Here, we report the first example that one enantiomer of a supramolecular cylinder can selectively stabilize human telomeric G-quadruplex DNA. The P-enantiomer of this cylinder has a strong preference for G-quadruplex over duplex DNA and, in the presence of sodium, can convert G-quadruplexes from an antiparallel to a hybrid structure. The compound's chiral selectivity and its ability to discriminate quadruplex DNA have been studied by DNA melting, circular dichroism, gel electrophoresis, fluorescence spectroscopy and S1 nuclease cleavage.

Green synthesis of nanowire-like Pt nanostructures and their catalytic properties

We reported a simple and effective green chemistry route for facile synthesis of nanowire-like Pt nanostructures atone step. In the reaction, dextran acted as a reductive agent as well as a protective agent for the synthesis of Pt nanostructures. Simple mixing of precursor aqueous solutions of dextran and K2PtCl4 at 80 degrees C could result in spontaneous formation of the Pt nanostructures. Optimization of the experiment condition could yield nanowire-like Pt nanostructures at 23:1 molar ratio of the dextran repeat unit to K2PtCl4.

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified by Nafion and ordered mesoporous silica-SBA-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

Selective hydrogenation of citral catalyzed with palladium nanoparticles in CO2-in-water emulsion

CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h(-1) has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h(-1)), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO(2)) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

Core Crosslinking of Biodegradable Block Copolymer Micelles Based on Poly(ester carbonate)

A biodegradable amphiphilic block copolymer, PEG-b-P(LA-co-MAC), was used to prepare spherical micelles consisting of a hydrophobic P(LA-co-MAC) core and a hydrophilic PEG shell. To improve their stability, the micelles were crosslinked by radical polymerization of the double bonds in the hydrophobic blocks. The crosslinked micelles had similar sizes and a narrow size distribution compared to their uncrosslinked precursor. The improved stability of the crosslinked micelles was confirmed by measurements of the CMC and a thermodynamic investigation. These micelles can internalize into Hela cells in vitro as demonstrated by inverted fluorescence microscopy and CLSM. These stabilized nanoscale micelles have potential use in biomedical applications such as drug delivery and disease diagnosis.

Spectral and electrochemical detection of protonated triplex formation by a small-molecule anticancer agent

Triplex helical formation has been the focus of considerable interest because of possible applications in developing new molecular biology tools as well as therapeutic agents and the possible relevance of H-DNA structures in biology system. We report here that a small-molecule anticancer agent, coralyne, has binding preference to the less stable protonated triplex d(C+-T)(6):d(A-G)(6).d(C-T)(6) over duplex d(A-G)(6).d(C-T)(6) and shows different spectral and electrochemical characteristics when binding to triplex and duplex DNA, indicating that electrochemical technique can detect the less stable protonated triplex formation.

Evaluation of Effects of Bivalent Cations on the Formation of Purine-rich Triple-Helix DNA by ESI-FT-MS

The GGA triplet repeats are widely dispersed throughout eukaryotic genomes. (GGA)n or (GGT)n oligonucleotides can interact with double-stranded DNA containing (GGA:CCT)n to form triple-stranded DNA. The effects of 8 divalent metal ions (3 alkaline-earth metals and 5 transition metals) on formation of these purine-rich triple-helix DNA were investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-MS). In the absence of metal ions, no triplex but single-strand, duplex, and purine homodimer ions were observed in mass spectra. The triple-helix DNA complexes were observed only in the presence of certain divalent ions. The effects of different divalent cations on the formation of purine-rich triplexes were compared. Transition-metal ions, especially Co2+ and Ni2+, significantly boost the formation of triple-helix DNA, whereas alkaline-earth metal ions have no positive effects on triplex formation. In addition, Ba2+ is notably beneficial to the formation of homodimer instead of triplex.

Prostate cancer cell-specific VEGF siRNA delivery system using cell targeting peptide conjugated polyplexes

A polymeric gene carrier was developed to deliver vascular endothelial growth factor (VEGF) small interfering RNA (siRNA) for prostate cancer cells in a target-specific manner. Prostate cancer-binding peptide (PCP) was conjugated with polyethylenimine (PEI) via a poly(ethylene glycol) (PEG) linker (PEI-PEG-PCP). The PEI-PEG-PCP conjugate could effectively condense siRNA to form stable polyelectrolyte complexes (polyplexes) with an average diameter of approximately 150 nm in an aqueous solution. VEGF siRNA/PEI-PEG-PCP polyplexes exhibited significantly higher VEGF inhibition efficiency than PCP-unmodified polycationic carriers (PEI-PEG or PEI) in human prostate carcinoma cells (PC-3 cells). The enhanced gene silencing activity of VEGF siRNA/PEI-PEG-PCP was maintained even under serum conditions, owing to the steric stabilization of the polyplexes with hydrophilic PEG grafts. Confocal microscopic studies revealed that the siRNA/PEI-PEG-PCP polyplexes were delivered into PC-3 cells in a PCP ligand-specific manner.