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 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Various stimuli-responsive composite particles with a high control of their internal structure and their corresponding hollow capsules are synthesized and characterized by photon correlation spectroscopy, TEM, and AFM. Core-shell particles with a silica core and a thermoresponsive shell are obtained by polymerization of N-isopropylacrylamide (NIPAM) in the presence of silica seeds grafted with a high density of gamma-methacryloxypropyltrimethoxysilane (MPS). The influence of the synthesis conditions is studied. The shell thickness increases when the monomer concentration increases in a limited range where uniform composite particles with a single core are obtained. At constant monomer concentration, the shell thickness does not depend on the size of the silica seeds, but the presence of free unbound microgels is observed when the silica surface area decreases. A range of particle diameters and shell thicknesses is thus obtained, which can lead to the corresponding hollow capsules by exposure to hydrofluoric acid solution. The volume phase transition temperature of these materials can be easily tuned by replacing the NIPAM monomer by another N-alkylacrylamide derivative. However, the incorporation of comonomers such as acrylic acid (AA) and a phenylboronic acid (PBA) derivative inhibits the formation of core-shell structures. In order to get pH or glucose responsiveness, these functional groups can be incorporated in the outer shell of a core-double shell structure, with pNIPAM as intermediate shell. pH-responsive and glucose-responsive composite particles are obtained by this method with a high control of their internal structure.
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PMID:Multiresponsive hybrid microgels and hollow capsules with a layered structure. 1928 Nov 53

N-acetylglucosamine, galactose, N-acetylgalactosamine and mannose and (or) glucose were present on specimens of two populations of Globodera rostochiensis and two of G. pallida representing four different pathotypes. Individuals within the pathotypes varied in the amounts of some of the saccharides present. The Pa population differed from the other populations in the presence on all individuals of N-acetylgalactosamine and the absence of extensive residues of mannose/glucose. TEM studies showed that N-acetylglucosamine and mannose/glucose were present on the exudate from the amphids of juveniles from the Ro population.
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PMID:Characterization and Localization of Saccharides on the Head Region of Four Populations of the Potato Cyst Nematode Globodera rostochiensis and G. pallida. 1929 33

This paper describes a new type of surface imprinting technique that combines the advantages of both the semi-covalent approach and one-stage miniemulsion polymerization. This process has been successfully applied for the preparation of glucose surface-imprinted nanoparticles. The selective artificial receptors for glucopyranoside were fully characterized by IR, TEM and BET analyses, and their molecular recognition abilities by binding experiments carried out in batch processes. The molecular affinity and selectivity of the glucose molecularly imprinted polymers were accurately quantified. These characteristics are essential for verification of the efficiency of the developed surface imprinting process. The imprinting effect was clearly demonstrated using the batch rebinding method. We have found that the glucose imprinted polymers produced using the optimized one-stage mini-emulsion exhibited quite fast kinetics of binding and equilibration with glucopyranoside templates, compared to polymers prepared by bulk polymerization technique, as well as extremely low levels of unspecific bindings. We also demonstrated that glucose molecular imprinted polymer (MIP) exhibited very good selectivity for its original template compared to other glycopyranoside derivatives, such as galactose. Finally, the extraction of the binding properties from isotherms of binding by fitting to the bi-Langmuir and Freundlich models allowed the determination of the affinity constant distribution of the binding sites. This imprinting protocol allowed the determination of an affinity constant (K(D)), involving exclusively H-bonding interactions, for the glucose MIP (P2C) with the best template 1, in CH3CN as the solvent system.
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PMID:Semi-covalent surface molecular imprinting of polymers by one-stage mini-emulsion polymerization: glucopyranoside as a model analyte. 1943 76

Aside from their superparamagnetic properties exploited in clinical magnetic resonance imaging (MRI), it was recently discovered that magnetic, iron oxide nanoparticles could function as an artificial, inorganic peroxidase. In this paper, we studied the impact of coating on the peroxidase activity of these nanoparticles. Nanoparticles with six different coating structures were synthesized and characterized by FTIR, TGA, TEM, size, zeta potential, and SQUID; and evaluated for peroxidase activity. Catalysis was found to follow Michaelis-Menten kinetics and peroxidase activity varied with respect to electrostatic affinity between nanoparticles and substrates, evidenced by differences in determined kinetic parameters. Glucose detection was selected as a model system because glucose could be indirectly measured from the release of hydrogen peroxide after its oxidation. Nanoparticles with high peroxidase activity exhibited higher sensitivity toward glucose, showing a larger linear slope when compared with those of low activity. A significantly improved linear correlation and detection limit of measured glucose could be readily obtained by manipulating the nanoparticle coating. Our findings suggest that iron oxide nanoparticles can be tailor-made to possess improved peroxidase-like activity. Such enhancements could further widen nanoparticle scope in glucose detection and extend its peroxidase functionality to other biomedical applications.
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PMID:The artificial peroxidase activity of magnetic iron oxide nanoparticles and its application to glucose detection. 1951 18

We intended to combine the liposomal preparation and the layer-by-layer deposition to prepare a nanosized capsule. Chitosan (CHI) was deposited to form the cationic polymeric layer onto a negatively charged liposomal surface and further deposition was carried out using anionic polymers dextran sulfate (DXS) or deoxyribonucleic acid (DNA). zeta-Potentials of nanocapsules changed between positive and negative charges at each deposition. FE-TEM revealed that the liposome remained a spherical shape even after the layer-by-layer (LbL) deposition. The capsule wall showed a dramatic increase in stability against the surfactant Triton X-100 compared to a bare liposome, and the stability was controllable by the adsorption amount of the polymer. These suggest that the polymer multilayer was generated on the liposome surface by the layer-by-layer depositions of polysaccharides. The three kinds of chemical substances with different charges, 1-hydroxy pyrene-3,6,8-trisulfonic acid (HPTS), alendronate, and glucose, were encapsulated into nanocapsules and the release was suppressed by the polymeric capsule wall irrespective of charges. The release from DNA-deposited nanocapsules (liponano-CHI-DNA) was clearly increased by raising temperature from 25 to 60 degrees C. This indicates that the temperature-dependent release was achieved by applying DNA denaturation as a temperature-dependent "switch", which influenced the permeability of the capsule wall.
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PMID:The preparation of sugar polymer-coated nanocapsules by the layer-by-layer deposition on the liposome. 1970 96

Nanostructure materials are attracting a great deal of attention because of their potential for achieving specific processes and selectivity, especially in biological and pharmaceutical applications. The generation of silver nanoparticles using optimized nitrate reductase for the reduction of Ag(+) with the retention of enzymatic activity in the complex is being reported. This report involves the optimization of enzyme activity to bring about enhanced nanoparticle synthesis. Response surface methodology and central composite rotary design (CCRD) were employed to optimize a fermentation medium for the production of nitrate reductase by Bacillus licheniformis at pH 8. The four variables involved in the study of nitrate reductase were Glucose, Peptone, Yeast extract and KNO(3). Glucose had a significant effect on nitrate reductase production. The optimized medium containing (%) Glucose: 1.5, Peptone: 1, Yeast extract: 0.35 and KNO(3): 0.35 resulted in a nitrate reductase activity of 452.206 U/ml which is same as that of the central level. The medium A (showing least nitrate reductase activity) and the medium B (showing maximum nitrate reductase activity) were compared for the synthesis. Spectrophotometric analysis revealed that the particles exhibited a peak at 431 nm and the A(431) for the medium B was 2-fold greater than that of the medium A. The particles were also characterized using TEM. The particles synthesized using the optimized enzyme activity ranged from 10 to 80 nm and therefore can be extended to various medicinal applications.
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PMID:Enhanced silver nanoparticle synthesis by optimization of nitrate reductase activity. 1979 22

The identification and characterization of Bacillus polyfermenticus KJS-2 (B. polyfermenticus KJS-2) was conducted using TEM, an API 50CHB kit, 16S rDNA sequencing, a phylogenetic tree, and catalase and oxidase testing. The conversion rate of glucose to lactic acid by B. polyfermenticus KJS-2 was found to be 60.71+/-4.9%. In addition, treatment of B. polyfermenticus KJS-2 with artificial gastric juice (pH 2.0) and bile acid (pH 6.5) for 4 h resulted in a final viability of 140+/-7.9% and 108+/-3.5%, respectively. Finally, the results of adhesion experiments using Caco-2 cells revealed that the adherence of B. polyfermenticus KJS-2 to Caco-2 cells was approximately 65+/-0.6%.
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PMID:Characterization of Bacillus polyfermenticus KJS-2 as a probiotic. 1980 60

Synthesis of cellulose in vitro is expected to afford tailor-made cellulosic materials with highly homogeneous structure compared to natural cellulosic materials. Here we report the enzymatic synthesis of cellulose II with high crystallinity from glucose and alpha-glucose 1-phosphate (alphaG1P) by cellodextrin phosphorylase (CDP). Although glucose had been believed not to act as a glucosyl acceptor of CDP, a significant amount of insoluble cellulose was precipitated without accumulation of soluble cello oligosaccharides when glucose was mixed with alphaG1P and CDP. This phenomenon can be explained in terms of the large difference in acceptor reactivity between glucose and cello oligosaccharides. (1)H NMR spectrometric analysis revealed that this insoluble cellulose had an average degree of polymerization (DP) of nine. TEM observation, together with electron and X-ray diffraction studies, indicated that the insoluble cellulose formed platelet-shaped single lamellar crystals of cellulose II, several mum in length and several hundred nm in width; this is large compared to reported cellulose crystals. The thickness of the lamellar crystal is 4.5nm, which is equivalent to a chain length of a cello oligosaccharide with DP nine and is consistent with the (1)H NMR spectroscopic results. These results suggest that cello oligosaccharides having an average DP of nine are synthesized in vitro by CDP when glucose is used as an acceptor, and the product forms highly crystalline cellulose II when it precipitates.
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PMID:Synthesis of highly ordered cellulose II in vitro using cellodextrin phosphorylase. 1987 58

Au(0)/POSS (Octa(aminophenyl) Silsesquioxane) composite was synthesized by chemical reduction of auric acid using glycerol as reducing agent. The morphology and physicochemical properties of Au/POSS nanocomposite were characterized by NMR, FT-IR and TEM spectroscopy. The Au/POSS nanocomposite electrode was used for the oxidation of glucose. The results indicate that the Au/POSS nanocomposite film was highly sensitive and suitable for glucose in 0.5 M NaOH. The presence of ascorbic acid in analyte gave no error in detection of glucose for measuring 5 mM glucose, which is the normal physiological level in blood. Further, Au/POSS nanocomposite showed an enhanced antibacterial activity even higher than standard ciprofloxacin. Hence, Au/POSS nanocomposite acts as a strong antibiocides as well as selective electrodes towards glucose oxidations.
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PMID:Synthesis and characterization of Au/POSS composite powder for bio-fuel cells and antibiotic applications. 1990 86

We demonstrate a one-pot hydrothermal cohydrolysis-carbonization process using glucose and iron nitrate as starting materials for the fabrication of carbonaceous spheres embedded with iron oxide nanoparticles. It is verified by TEM, (57)Fe Mossbauer, and Fe K-edge XAS that iron oxide nanoparticles are highly dispersed in the carbonaceous spheres, leading to a unique microstructure. A formation mechanism is also proposed. This route is also applicable to a range of other naturally occurring saccharides and metal nitrates. A catalytic study revealed the remarkable stability and selectivity of the reduced Fe(x)O(y)@C spheres in the Fischer-Tropsch synthesis, which clearly exemplifies the promising application of such materials.
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PMID:Fe(x)O(y)@C spheres as an excellent catalyst for Fischer-Tropsch synthesis. 2002 26


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