Silver colloid nanoparticles: synthesis, characterization, and their antibacterial activity

A one-step simple synthesis of silver colloid nanoparticles with controllable sizes is presented. In this synthesis, reduction of [Ag(NH(3))(2)](+) complex cation by four saccharides was performed. Four saccharides were used: two monosaccharides (glucose and galactose) and two disaccharides (maltose and lactose). The syntheses performed at various ammonia concentrations (0.005-0.20 mol L(-1)) and pH conditions (11.5-13.0) produced a wide range of particle sizes (25-450 nm) with narrow size distributions, especially at the lowest ammonia concentrations. The average size, size distribution, morphology, and structure of particles were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), and UV/Visible absorption spectrophotometry. The influence of the saccharide structure (monosacharides versus disaccharides) on the size of silver particles is briefly discussed. The reduction of [Ag(NH(3))(2)](+) by maltose produced silver particles with a narrow size distribution with an average size of 25 nm, which showed high antimicrobial and bactericidal activity against Gram-positive and Gram-negative bacteria, including highly multiresistant strains such as methicillin-resistant Staphylococcus aureus. Antibacterial activity of silver nanoparticles was found to be dependent on the size of silver particles. A very low concentration of silver (as low as 1.69 mug/mL Ag) gave antibacterial performance.     

Construction of Glycosylated Surfaces for Poly(propylene) Beads with a Photoinduced Grafting/Chemical Reaction Sequence

Surface modification of commercial PPBs with different saccharides is described. Surface‐glycosylated PPBs were prepared through reaction between the hydroxyl groups of poly(HEMA) and acetylated saccharides such as α‐glucose pentaacetate, β‐galactose pentaacetate, and lactose octaacetate. The modified PPBs were characterized by XPS and water contact angle measurement. It was found that the grafting degree of poly(HEMA) increases with UV irradiation time, monomer concentration, and water content in solvent. The binding degree of monosaccharides is higher than that of disaccharides. The glycosylated PPBs can selectively recognize lectins, indicating potential for protein isolation.

     

Dendritic galactosides based on a beta-cyclodextrin core for the construction of site-specific molecular delivery systems: synthesis and molecular recognition studies

In order to evaluate the ability of multivalent glycosides based on a beta-cyclodextrin core as site-specific molecular carriers, a study on both the inclusion complexation behaviour and lectin binding affinity of branched and hyperbranched beta-cyclodextrins is presented. A series of cluster galactosides constructed on beta-cyclodextrin scaffolds containing seven 1-thio-beta-lactose or beta-lactosylamine bound to the macrocyclic core through different spacer arms were synthesised. In addition, the first synthesis of three first-order dendrimers based on a beta-cyclodextrin core containing fourteen 1-thio-beta-D-galactose, 1-thio-beta-lactose and 1-thio-beta-melibiose residues was performed. Calorimetric titrations performed at 25 degrees C in buffered aqueous solution (pH 7.4) gave the affinity constants and the thermodynamic parameters for the complex formation of these beta-cyclodextrin derivatives with guests sodium 8-anilino-1-naphthalenesulfonate (ANS) and 2-naphthalenesulfonate, and lectin from peanut (Arachis hypogaea) (PNA). The persubstitution of the primary face of the beta-cyclodextrin with saccharides led to a slight increase of the binding constant values for the inclusion complexation with ANS relative to the native beta-cyclodextrin. However, the increase of the steric congestion due to the presence of the saccharide residues on the narrow rim of the beta-cyclodextrin may cause a decrease of the binding ability as shown for sodium 2-naphthalenesulfonate. The spacer arms are not passive elements and influence the host binding ability according to their chemical nature. PNA forms soluble cross-linked complexes with cluster galactosides and lactosides scaffolded on beta-cyclodextrin but not with cluster galactopyranosylamines or melibiose. Both, perbranched and hyperbranched beta-cyclodextrins, form stronger complexes with PNA than the monomeric analogues. However, the use of hyperbranched CDs does not contribute to the improvement of the complex stability relative to heptakis-glycocyclodextrin derivatives. Finally, a titration experiment with PNA and a complex formed by a heptakis lactose beta-cyclodextrin derivative with sodium 2-naphthalenesulfonate showed the formation of a soluble cross-linked complex with stronger affinity constant and higher stoichiometry than those observed for the complex formation of PNA with the same heptakis-lactose beta-cyclodextrin derivative, suggesting the formation of a three component complex.     

Boronic acid based peptidic receptors for pattern-based saccharide sensing in neutral aqueous media, an application in real-life samples

The advent of the alternative sweeteners market has signaled a demand for chemosensors which target multiple saccharides and saccharide derivatives, in aqueous media at physiological pH. This demand has largely been unmet as existing molecular receptors for saccharides have generally not shown sufficient degrees of affinity and selectivity in aqueous media. A chemosensor array for saccharides and saccharide derivatives, fully operational in aqueous media at physiological pH, has been developed and is reported herein. Boronic acid based peptidic receptors, derived from a combinatorial library, served as the cross-reactive sensor elements in this array. The binding of saccharides to these receptors was assessed colorimetrically using an indicator uptake protocol in the taste-chip platform. The differential indicator uptake rates of these receptors in the presence of saccharides were exploited in order to identify patterns within the data set using linear discriminant analysis. This chemosensor array is capable of classifying disaccharides and monosaccharides as well as discriminating compounds within each saccharide group. Disaccharides have also been distinguished from closely related reduced-calorie counterparts. This linear discriminant analysis set was then employed as a training set for identifying a specific saccharide in a real-world beverage sample. The methodology developed here augurs well for use in other real-world samples involving saccharides as well as for sensing other desired analytes.     

Protection of protein secondary structure by saccharides of different molecular weights during freeze-drying

The protective effects of saccharides with various molecular weights (glucose, maltose, maltotriose, maltotetraose, maltopentaose, maltoheptaose, dextran 1060, dextran 4900, and dextran 10200) against lyophilization-induced structural perturbation of model proteins (BSA, ovalbumin) were studied. Fourier transform infrared (FT-IR) analysis of the proteins in initial solutions and freeze-dried solids indicated that maltose conferred the greatest protection against secondary structure change. The structure-stabilizing effect of maltooligosaccharides decreased in increasing the number of saccharide units. Larger molecules of dextran also showed a smaller structure-stabilizing effect. Increasing the effective saccharide molecular size by a borate-saccharide complexation reduced the protein structure-stabilizing effect of all of the saccharides except glucose. The results indicate that the larger saccharide molecules, and/or the complex formation with borate ion, reduce the free and accessible hydroxyl groups to interact with and stabilize the protein structure by a water-substitution mechanism.     

Depolarization thermocurrents in frozen aqueous solutions of mono- and di-saccharides

The dielectric behaviour of frozen aqueous solutions of the monosaccharides glucose, galactose, mannose, ribose and arabinose and the disaccharides cellobiose, lactose and maltose was studied by the depolarization thermocurrent (DTC) method in the temperature range 80–270 K and over a wide range of concentrations (0.0003–1.5 mol/l), to obtain information on the state of water in the solutions. The results show that the saccharides studied can be subdivided into two classes regarding their hydration behaviour. The solutions of glucose, galactose and mannose are characterized by a continuous transition from hydration (i.e. affected by the solute molecule) to free (i.e. non-affected) H₂O molecules. The solutions of ribose, arabinose, cellobiose, lactose and maltose are characterized by the presence of two dicrete kinds of H₂O molecules, namely free and hydration molecules. These results are discussed in terms of a hydration model.     

Synthesis and biological application of glycopolymers

Saccharides on the cell surfaces participate in a number of biochemical phenomena via the protein–saccharide interaction. Synthetic glycopolymers mimic the function of the cell‐surface saccharides and efficiently interact with proteins, cells, and pathogens based on the multivalent effect. Since the biological functions of saccharides are paid much attention, the glycopolymers are being increasingly explored as biomaterials for medicinal application and tissue engineering. This review presents a practical approach of glycopolymers. The glycopolymers were prepared by the facile syntheses of poly(vinyl saccharide)s and the physical and biological properties were introduced. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5031–5036, 2007     

Rapid differentiation of simple saccharides based on cluster ions by paper spray tandem mass spectrometry

Simple saccharides have a variety of biological functions, but their structural diversity and inherent structural features pose a major challenge for rapid analysis. In this work, we developed a derivative-free and ion mobility-free method for the rapid analysis of monosaccharides and disaccharides using paper spray tandem mass spectrometry. Trimeric cluster ions consisting of saccharide analytes, ligands and transition metal ions are used as precursor ions. We defined the R-value as the ratio of the intensity of the product ion that loses one molecule of ligand over the intensity of the product ion that loses one molecule of saccharide via collision induced dissociation (CID). The species and conformation of simple saccharides can be easily differentiated by calculating this R-value. With the capability of directly analyzing clinical samples using paper spray ionization, our method can be used to rapidly quantify the molar ratio of galactose to glucose in dried plasma samples to aid in the diagnosis of galactosemia. The analytical strategy provided herein has good potential to be applied to a wide range of saccharide analysis applications in the future.     

Noncovalent fluorous interactions for the synthesis of carbohydrate microarrays

A surface patterning method based on noncovalent immobilization of fluorous-tagged sugars on fluorous-derivatized glass slides allows the facile fabrication of carbohydrate microarrays. To expand the scope of these arrays, the first syntheses are reported of arabinose, rhamnose, lactose, maltose, and glucosamine tagged with a single C₈F₁₇-tail for ease of purification as well as array formation. Screening of these carbohydrate microarrays against lectins from Triticum vulgaris (WGA) and Arachis hypogaea (PNA) demonstrate that the noncovalent fluorous–fluorous interaction is sufficient to retain not only mono- but also disaccharides under the biological assay conditions.     

Far infrared study of some mono- and disaccharides

Some mono- and disaccharides were studied using the far infrared (FIR) spectroscopic method. Results show that every saccharide has a characteristic spectrum pattern. It is useful to distinguish between different saccharides based on the sequence of their relative intensities. Therefore, an encoding method was suggested to label each substance. In this investigation, the FIR spectra of the saccharides were demonstrated using the encoding method and prove the feasibility of the method.     

Non-covalently lactose imprinted polymers and recognition of saccharides in aqueous solutions

The aim of this work was to prepare lactose imprinted polymer and study of its selectivity for the recognition of different mono- and disaccharides. A series of molecularly imprinted polymers (MIPs) against lactose were synthesized and their binding properties were compared with a Blank non-imprinted polymer. Methacrylamide (MAAM) and ethylene glycol dimethacrylate were used as functional monomer and cross-linker, respectively. Dimethylsulfoxide was also applied as polymerization solvent. Different lactose:MAAM ratios were applied and optimized MIP was selected in a conventional batch adsorption study. The dissociation constant and maximum binding sites of polymer were determined using the Scatchard analysis. The selectivity of MIP for different mono- and disaccharides was also evaluated. The results indicated that the shape of cavity and orientation of functional monomers in binding sites and the spatial arrangement of hydroxyl groups in saccharide structure were responsible for the selectivity of lactose imprinted polymer.     

Determination of saccharides in sake by high-performance liquid chromatography with polarized photometric detection

A high-performance liquid chromatographic method has been developed for the determination of saccharides in sake, an alcoholic beverage brewed from rice. Saccharides in sake were separated on a normal phase (carbamoyl bonded silica) column using a linear gradient elution of water in acetonitrile. Seven saccharides, glucose, maltose, isomaltose, maltotriose, panose, isomaltotriose and ethyl alpha-D-glucoside, were determined by a polarized photometric detector. Unidentified peaks suggesting saccharides with polymerization degrees over 4 were also observed. The proposed method did not require any sample clean-up treatment. As an application, saccharide compositions in various kinds of sake were compared.     

Noncovalently galactose imprinted polymer for the recognition of different saccharides

Molecularly imprinted polymers (MIPs) represent a new class of materials possessing high selectivity and affinity for the target molecule. The main goal of this study was to prepare a galactose imprinted polymer and its potential application for the recognition of different saccharides. The selectivity of galactose imprinted polymer for several saccharides; glucose, mannose, fructose, maltose, lactose, sucrose and raffinose was investigated. Macroporous polymer was prepared utilizing ethyleneglycoldimethacrylate as a crosslinking agent, in the presence of galactose as a template molecule with acrylamide as a functional monomer. After the synthesis of polymer, galactose was removed by methanol:acetic acid washing. The selectivity of galactose imprinted polymer for other saccharides was utilized by batch rebinding assay. The arrangement of functional groups within cavities versus shape selectivity is discussed. The results showed that, the orientation of the functional groups was the dominating factor for the selectivity of galactose imprinted polymer. The dissociation constants of polymer were determined by Scatchard analysis.     

Propargyl glycosides as stable glycosyl donors: anomeric activation and glycoside syntheses

The advantages of stable glycosyl donors for saccharide coupling are many, and we describe herein the utility of propargyl glycosides for anomeric activation and glycoside synthesis exploiting the alkynophilicity of AuCl3. Various aglycones were reacted with propargyl glycosides, resulting in the formation of an alpha,beta-mixture of glycosides and disaccharides in good yields.     

Development of a gas diffusion probe for the rapid measurement of pCO2 in aquatic samples

A capillary electrophoresis (CE) procedure with contactless conductivity detection (C(4)D) has been developed for monitoring of neutral mono- and disaccharides in drinks and foodstuffs. The separation of a mixture of seven neutral saccharides (glucose, fructose, galactose, mannose, ribose, sucrose and lactose) employed a quartz capillary, 5 μm i.d., with an effective length of 18.3 cm, and 75 mM NaOH (pH 12.8) as the background electrolyte (BGE). The limit of detection (LOD) values obtained lied within a range from 0.4 μmol L(-1) for lactose to 0.9 μmol L(-1) for ribose, with a separation time shorter than 140 s. The procedure was successfully applied to determinations of saccharides in fruit juices, Coca-Cola, milk, red and white wines, yoghurts, honey and a foodstuff additive.     

Quantification of Saccharides in Honey Samples Through Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Using HgTe Nanostructures

Quantification of monosaccharides and disaccharides in five honey samples through surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using HgTe nanostructures as the matrix and sucralose as an internal standard has been demonstrated. Under optimal conditions (1× HgTe nanostructure, 0.2 mM ammonium citrate at pH 9.0), the SALDI-MS approach allows detection of fructose and maltose at the concentrations down to 15 and 10 μM, respectively. Without conducting tedious sample pretreatment and separation, the SALDI-MS approach allows determination of the contents of monosaccharides and disaccharides in honey samples within 30 min, with reproducibility (relative standard deviation <15%). Unlike only sodium adducts of standard saccharides detected, sodium adducts and potassium adducts with differential amounts have been found among various samples, showing different amounts of sodium and potassium ions in the honey samples. The SALDI-MS data reveal that the contents of monosaccharides and disaccharides in various honey samples are dependent on their nectar sources. In addition to the abundant amounts of monosaccharides and disaccharides, oligosaccharides in m/z range of 650???2700 are only detected in pomelo honey. Having advantages of simplicity, rapidity, and reproducibility, this SALDI-MS holds great potential for the analysis of honey samples.

Boronate affinity saccharide electrophoresis: a novel carbohydrate analysis tool

The incorporation of specialised carbohydrate affinity ligand methacrylamido phenylboronic acid in polyacrylamide gels for fluorophore-assisted carbohydrate electrophoresis greatly improved the effective separation of saccharides that show similar mobilities in standard electrophoresis. Polyacrylamide gel electrophoresis using methacrylamido phenylboronic acid in low loading (typically 0.5-1% dry weight) was unequivocally shown to alter retention of labelled saccharides depending on their boronate affinity. While conventional fluorophore-assisted carbohydrate electrophoresis of 2-aminoacridone labelled glucose oligomers showed an inverted parabolic migration, an undesired trait of small oligosaccharides labelled with this neutral fluorophore, boron affinity saccharide electrophoresis separation of these carbohydrates completely restored their predicted running order, based on their charge/mass ratio, and resulted in improved separation of the analyte saccharides. These results exemplify boron affinity saccharide electrophoresis as an important new technique for analysing carbohydrates and sugar-containing molecules.     

The alpha,alpha-(1-->1) linkage of trehalose is key to anhydrobiotic preservation

This study compares the efficacy of six disaccharides and glucose for the preservation of solid supported lipid bilayers (SLBs) upon exposure to air. Disaccharide molecules containing an alpha,alpha-(1-->1) linkage, such as alpha,alpha-trehalose and alpha,alpha-galacto-trehalose, were found to be effective at retaining bilayer structure in the absence of water. These sugars are known to crystallize in a clam shell conformation. Other saccharides, which are found to crystallize in more open structures, did not preserve the SLB structure during the drying process. These included the nonreducing sugar, sucrose, as well as maltose, lactose, and the monosaccharide, glucose. In fact, even close analogs to alpha,alpha-trehalose, such as alpha,beta-trehalose, which connects its glucopyranose rings via a (1-->1) linkage in an axial, equatorial fashion, permitted nearly complete delamination and destruction of supported bilayers upon exposure to air. Lipids with covalently attached sugar molecules such as ganglioside GM1, lactosyl phosphatidylethanolamine, and glucosylcerebroside were also ineffective at preserving bilayer structure. The liquid crystalline-to-gel phase transition temperature of supported phospholipid bilayers was tested in the presence of sugars in a final set of experiments. Only alpha,alpha-trehalose and alpha,alpha-galacto-trehalose depressed the phase transition temperature, whereas the introduction of other sugar molecules into the bulk solution caused the phase transition temperature of the bilayer to increase. These results point to the importance of the axial-axial linkage of disaccharides for preserving SLB structure.     

Thermodynamic evidence for Ca2+-mediated self-aggregation of Lewis X gold glyconanoparticles. A model for cell adhesion via carbohydrate-carbohydrate interaction

Thermodynamic evidence for the selective Ca(2+)-mediated self-aggregation via carbohydrate-carbohydrate interactions of gold glyconanoparticles functionalized with the disaccharides lactose (lacto-Au) and maltose (malto-Au), or the biologically relevant trisaccharide Lewis X (Le(X)-Au), was obtained by isothermal titration calorimetry. The aggregation process was also directly visualized by atomic force microscopy. It was shown in the case of the trisaccharide Lewis X that the Ca(2+)-mediated aggregation is a slow process that takes place with a decrease in enthalpy of 160 +/- 30 kcal mol(-)(1), while the heat evolved in the case of lactose and maltose glyconanoparticles was very low and thermal equilibrium was quickly achieved. Measurements in the presence of Mg(2+) and Na(+) cations confirm the selectivity for Ca(2+) of Le(X)-Au glyconanoparticles. The relevance of this result to cell-cell adhesion process mediated by carbohydrate-carbohydrate interactions is discussed.     

Synthesis of silver/poly(2-hydroxyethyl methacrylate) particles via a combination of inverse miniemulsion and silver ion reduction in a "nanoreactor"

Silver salt/poly(2-hydroxyethyl methacrylate) (poly(HEMA)) hybrid particles were first prepared by inverse miniemulsion polymerization of 2-hydroxyethyl methacrylate (HEMA) with silver tetrafluoroborate (AgBF(4)) as a lipophobe. High silver salt loads of up to 13% with respect to the disperse phase were achieved. The silver/poly(HEMA) hybrid particles were subsequently formed via a gas-phase in situ reduction of AgBF(4) by hydrazine on the surfaces of silver salt/poly(HEMA) particles. The formation of silver nanoparticles was confirmed by UV-vis spectroscopy and X-ray diffraction. The morphology of the hybrid particles of silver salt/poly(HEMA) and silver/poly(HEMA) was fully characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and dynamic light scattering (DLS). The influence of the reaction parameters including the type and amount of cosolvent, salt content, and type of surfactant on the particle properties and colloidal stability during the reduction process was thoroughly investigated.