Formation of nanostructured materials via coalescence of amphiphilic hollow particles

A new, simplified route to amphiphilic core-shell nanotubes, microfibers, and microrods has been developed that does not involve the traditional utilization of well-defined block copolymers. Thus, amphiphilic graft copolymers (PEI-g-PMMA) are prepared by an aqueous free radical polymerization that self-assemble in situ to form uniform core-shell nanoparticles. The hydrophobic homopolymer (PMMA) that is also formed is incorporated in the cores. Slight cross-linking of the shells followed by extraction of the homopolymer results in hollow nanoparticles that coalesce to form nanotubes. When the shells are not cross-linked, the hollow particles coalesce to form microrods and microfibers. The sizes and shapes of the micromaterials can be controlled by varying the experimental conditions.     

Dispersion stability of a ceramic glaze achieved through ionic surfactant adsorption

The adsorption of cetylpyridinium chloride (CPC) and sodium dodecylbenzenesulfonate (SDBS) onto a ceramic glaze mixture composed of limestone, feldspar, quartz, and kaolin has been investigated. Both adsorption isotherms and the average particle zeta potential have been studied in order to understand the suspension stability as a function of pH, ionic strength, and surfactant concentration. The adsorption of small amounts of cationic CPC onto the primarily negatively charged surfaces of the particles at pH 7 and 9 results in strong attraction and flocculation due to hydrophobic interactions. At higher surfactant concentrations a zeta potential of more than +60 mV results from the bilayered adsorbed surfactant, providing stability at salt concentrations < or = 0.01 M. At 0.1 M salt poor stability results despite substantial zeta potential values. Three mechanisms for SDBS adsorption have been identified. When anionic SDBS monomers either adsorb by electrostatic interactions with the few positive surface sites at high pH or adsorb onto like charged negative surface sites due to dispersion or hydrophobic interactions, the magnitude of the negative zeta potential increases slightly. At pH 9 this increase is enough to promote stability with an average zeta potential of more than -55 mV, whereas at pH 7 the zeta potential is lower at about -45 mV. The stability of suspensions at pH 7 is additionally due to steric repulsion caused by the adsorption of thick layers of neutrally charged Ca(DBS)2 complexes created when the surfactant interacts with dissolved calcium ions from the calcium carbonate component.     

Preparation and characterization of microwave-treated carboxymethyl chitin and carboxymethyl chitosan films for potential use in wound care application

CM-chitin and CM-chitosan films were successfully crosslinked by microwave treatment. Crosslinking of the microwave-treated CM-chitin films involved mainly the carboxylate and the secondary alcohol groups, while crosslinking of microwave-treated CM-chitosan films involved the carboxylate and the amino groups. In addition, the crystallinity of CM-chitin increased with increasing microwave treatment time, whereas an increase in the crystallinity of the microwave-treated CM-chitosan films was not observed. At a similar percentage of weight loss, the crosslinking of either CM-chitin or CM-chitosan films by microwave treatment required much less stringent condition when compared with the crosslinking by autoclave treatment. Based on both direct and indirect cytotoxicity assays, the cytotoxicity of the microwave-treated CM-chitin films was negative, while that of the microwave-treated CM-chitosan films was positive. Human fibroblasts adhered on the surface of microwave-treated CM-chitosan films much better than on the surface of microwave-treated CM-chitin films.     

Preparation and characterization of chitin whisker-reinforced silk fibroin nanocomposite sponges

For highly porous form such as sponges or scaffolds, the induction of the β-sheet formation of silk fibroin to make the water-stable materials usually results in their high shrinkage leading to a difficulty in controlling shape and size of materials. Thus, the objective of this study was to improve dimensional stability of silk fibroin sponge by incorporating chitin whiskers as nanofiller. Chitin whiskers exhibited the average length and width of 427 and 43 nm, respectively. Nanocomposite sponges at chitin whiskers to silk fibroin weight ratio (C/S ratio) of 0, 1/8, 2/8, or 4/8 were prepared by using a freeze-drying technique. The dispersion of chitin whiskers embedded in the silk fibroin matrix was found to be homogeneous. The presence of chitin whiskers embedded into silk fibroin sponge not only improved its dimensional stability but also enhanced its compression strength. Regardless of the chitin whisker content, SEM micrographs showed that all samples possessed an interconnected pore network with an average pore size of 150 μm. To investigate the feasibility of the nanocomposites for tissue engineering applications, L929 cells were seeded onto their surfaces, the results indicated that silk fibroin sponges both with and without chitin whiskers were cytocompatible. Moreover, when compared to the neat silk fibroin sponge, the incorporation of chitin whiskers into the silk fibroin matrix was found to promote cell spreading.     

Selective conversion of fructose into 5-ethoxymethylfurfural over green catalyst

Research on Chemical Intermediates - In this study, selective formation of 5-ethoxymethylfurfural (EMF) from one-pot conversion of fructose in a co-solvent of ethanol with tetrahydrofuran over...     

Cordycepin Sensitizes Cholangiocarcinoma Cells to Be Killed by Natural Killer-92 (NK-92) Cells

Immunotherapy harnessing immune functions is a promising strategy for cancer treatment. Tumor sensitization is one approach to enhance tumor cell susceptibility to immune cell cytotoxicity that can be used in combination with immunotherapy to achieve therapeutic efficiency. Cordycepin, a bioactive compound that can be extracted from some Cordyceps spp. has been reported to effectively inhibit tumor growth, however, the mechanism of its tumor sensitization activity that enhances immune cell cytotoxicity is unknown. In the present study, we investigated the potency of cordycepin to sensitize a lethal cancer, cholangiocarcinoma (CCA), to natural killer (NK) cells. Treatment with cordycepin prior to and during co-culturing with NK-92 cells significantly increased cell death of KKU-213A as compared to solitary cordycepin or NK treatment. Moreover, sensitization activity was also observed in the combination of NK-92 cells and Cordyceps militaris extract that contained cordycepin as a major component. The cordycepin treatment remarkably caused an increase in TRAIL receptor (DR4 and DR5) expression in KKU-213A, suggesting the possible involvement of TRAIL signaling in KKU-213A sensitization to NK-92 cells. In conclusion, this is the first report on the sensitization activity of cordycepin on CCA cells to NK cytotoxicity, which supports that cordycepin can be further developed as an alternate immunomodulating agent.     

The essential role of Fe(III) ion removal over efficient/low-cost activated carbon: surface chemistry and adsorption behavior

Research on Chemical Intermediates - The efficient/low-cost activated carbons were prepared from inedible fruits such as Cerbera odollam Gaertn, Terminalia catappa, Ficus lyrata, Couroupita...     

Adsorption behavior of As(V) from aqueous solution by using Fe3+–MnO4−-modified activated carbon (Leucaena leucocephala (Lam) de Wit)

Research on Chemical Intermediates - The objective of this work was to prepare a highly efficient adsorbent from Leucaena leucocephala (Lam) de Wit via pyrolysis and chemical activation (H3PO4)...     

Miscibility and biodegradability of silk fibroin/carboxymethyl chitin blend films

Blend films of silk fibroin and carboxymethyl chitin were prepared by solution casting using water as a cosolvent. The blend films were subjected to post-treatment with an aqueous methanol solution to induce beta-sheet formation of silk fibroin. The miscibility of the blend films both before and after methanol treatments was investigated in terms of chemical interactions, morphologies, thermal properties, and crystal structures by using FTIR spectroscopy, SEM, DSC, and XRD. The results indicate that the blend between silk fibroin and CM-chitin was semi-miscible because only the amorphous parts of the polymers were compatible with each other. The enzymatic degradation showed that the incorporation of CM-chitin enhanced biodegradability and swelling ability of silk fibroin.     

Preparation of PMMA/acid-modified chitosan core-shell nanoparticles and their potential as gene carriers

The core-shell nanoparticles consisting of poly(methyl methacrylate) (PMMA) cores surrounded by various acid-modified chitosan shells were synthesized using a surfactant-free emulsion copolymerization, induced by a tert-butylhydroperoxide (TBHP) solution. Methyl methacrylate (MMA) was grafted onto four acid-modified chitosans (hydrochloric, lactic, aspartic, and glutamic acids) with MMA conversions up to 64%. The prepared nanoparticles had diameter ranging from 100 to 300 nm characterized by atomic force microscopy and displayed highly positive surface charges up to +77 mV. Transmission electron microscopic images clearly revealed well-defined core-shell morphology of the nanoparticles where PMMA cores were coated with acid-modified chitosan shells. The effect of acid-modified chitosans on particle size, intensity of surface charge, morphology, and thermal stability were determined systematically. The plasmid DNA/nanoparticles complexes were investigated with ζ-potential measurement. The results suggested that these nanoparticles can effectively complex with plasmid DNAs via electrostatic interaction and could be used as gene carriers.