M. V. Lesnichaya

Formation kinetics of gold nanoparticles in the galactomannan polysaccharide matrix

282 Gold nanoparticles and nanocomposites based on them are finding more and more extensive use as highly effective catalysts of various chemical processes [1], optical sensors of biospecific interactions [2], agents for the targeted drug delivery [2] and photo thermolysis of cancer cells [3], inhibitors of autoim mune diseases [4], etc. However, the problem of ther modynamic instability of nanoparticles caused by excess of their surface energy has not still been ulti mately solved [5, 6]. This problem is addressed using stabilizing polymeric matrices of synthetic and natural origin, in particular, polysaccharides, which impart a specific set of additional physicochemical and biolog ical properties to nanoparticles [7, 8]. Galactomannan is a natural water soluble polysac charide widely used in food and pharmaceutical industries [9]. Previously, it was used to prepare bio logically active nanocomposites containing silver metal nanoparticles [10]. Here we report on the results of synthesis of bio compatible aggregation stable nanocomposites con sisting of zerovalent gold nanoparticles stabilized by galactomannan macromolecules. The macromolecule of this polysaccharide (MM 1300 kDa) consists of 1,4 β polymannopyranoside chain with single α galactopyranose side branches. The Man : Gal ratio determined by quantitative 13C NMR spectroscopy is 1.6 [10].

Synthesis of silver-containing nanocomposites based on humic substances of brown coal and their antioxidant activity

72 Silver nanoparticles and nanomaterials based on them exhibit a broad spectrum of biological properties and are multipurpose means for biomedicine [1, 2]. Indeed, the antimicrobial activity of silver nanoparti cles with respect to living cells may be determined by their size, shape, ligand environment, and particular preparation method [3, 4]. One of the most conve nient and environmentally safe methods for the syn thesis of metallic nanoparticles is reduction of a metal containing precursor in water in the presence of a sta bilizer for the formed nanoparticles (these may be polyhydric alcohols [5, 6], polysaccharides [7, 8], polyphenols [9, 10], and the like).

Molecular-weight characteristics of galactomannan and carrageenan

It was established that the action of [H+] at concentration 1.96∙10–2 M at 90°C for 5–20 min decreased sharply the molecular weight of galactomannan and carrageenan and increased their overall reductive capability. The action of [OH–] at concentrations 2.6∙10–2 and 26∙10–2 under the same conditions was characterized by a slow decrease of the molecular weight and retention of the functionality of the polysaccharides. It was shown that modified galactomannan and κ-carrageenan exhibited increased watersolubility while retaining the structure and gel-forming and stabilizing capabilities and degree of sulfation (for carrageenan).

New nanobiocomposites of ammonium magnesium phosphate and carrageenan as efficient prebiotics

144 It is known that normal functioning of a human or animal body requires a balanced qualitative and quan titative composition of intestinal microbiocenosis [1, 2]. The intestinal microflora forms the systemic and tissue immunity, and participates in the fat and pigment metabolism, digestive enzyme production, and endogenous synthesis of vitamins and substances hav ing bactericidal action on pathogenic organisms [3, 4]. A considerable stimulating effect on the generation, growth, and functional activity of the microflora is exerted by food biopolymers (prebiotics), which are not digested or uptaken in the upper gastrointestinal tract of the host organism but are efficiently bioutilized by the colonic microflora.

Effect of silver nanoparticles on the thermal characteristics of nanocomposites of galactose-containing polysaccharides

187 Considerable recent attention has focused on design of nanostructured drugs [1–3]. Enhanced interest in them stems from their improved pharmaco logical properties as compared with known materials [3–6]. We have designed silver containing nanocom posites based on natural biopolymers arabinogalactan, galactomannan, and carrageenan [7–9]. The nano composites synergistically combine the properties of the polysaccharide matrix—solubility in water, non toxicity, and biocompartibility—with the antimicro bial and optical properties of silver nanoparticles [7, 9–11]. For biomedical and technical application of the synthesized silver containing nanobiocomposites, of crucial importance is the extent of their stability to heating in the course of sterilization in medicine or on exposure to laser light in plasmon technologies. Inas much as polysaccharides are thermoactive substances, it is necessary to study the behavior of composite materials based on them at elevated temperatures.

Features of gold nanoparticle formation in matrices of humic substances of different origin

One of environmentally friendly methods of prep aration of biocompatible metal nanoparticles consists in the reduction of their precursors in aqueous medium in the presence of a reagent that simulta neously behaves as both a reducing agent and a stabi lizer for resultant nanoparticles [3–6]. Such promising materials for the synthesis of metal nanoparticles are humic substances (HSs), which are a set of com pounds of polyaromatic, polysaccharide, and other biopolymer nature [7].

Estimation of the antioxidant activity of humic substances from various natural sources of Mongolia

Humic substances are a set of polyaromatic and carbohydrate organic compounds. They are formed in soils and bottom sediments upon microbiological decomposition of plant and animal organisms. The functional composition of humic substances com� prises characteristic polar functional groups COOH, OH, CO, and NH2 , and long alkyl side chains of fatty acids [1, 2]. This polyfunctional character of humic macromolecules, apart from the highly conjugated structure of the polyaromatic moieties, gives rise to valuable biological properties of these macromole� cules, in particular, antioxidant activity. The elemental and functional composition, the structure, and prop� erties of humic substances vary depending on their source. This paper reports on the first results of a compar� ative study of the antioxidant activities of humic sub� stances isolated from various natural sources of Mon� golia. The humic substances isolated from the therapeu� tic mud of the Mongolian lake Gurvan Nuur, brown coal from the Baga Nuur deposit, and shales from the Shine Hudag deposit are black crystalline powders with the total ash content of 20–22 wt %. The degree of oxidation (O/C) varies from 0.65 to 0.86, the high� est value being typical of humic substances from the lake. The H/C ratio varies in the range from 0.067 to

Metal-polymer nanobiocomposites with galactose-containing stabilizing matrices: Dimensional effect in changes of molar mass parameters

Molar mass parameters of galactose-containing polysaccharides constituting composites with noble metal nanoparticles have been determined by means of Size-exclusion chromatography (SEC). The composites are self-assembled via specific interaction of the biopolymers with the surface of the metal nanoparticles. The metal content significantly influences the molar mass parameters of the stabilizing polysaccharides. The change of the polymer of polydispersity is due to their redox interaction with the metal ions as well as due to the alkaline-induced degradation. Increasing the nanoparticles number results in the enhanced macromolecules aggregation.

Silver-containing nanocomposites with antioxidant activity based on humic substances of different origin

Humic substances isolated from curative mud, brown coal, and shale of the Mongolian deposits were used for the synthesis of water-soluble silver-containing nanocomposites. The humic substances from curative mud have the highest reducing and stabilizing ability among the studied objects. The compositions and structures of the obtained nanocomposites were characterized in detail by a complex of modern physicochemical methods. The humic substances and related nanocomposites were found to exhibit high antioxidant activity comparable with that of the known antioxidants.

Chiroplasmonic magnetic gold nanocomposites produced by one-step aqueous method using κ-carrageenan

Novel water-soluble chiroplasmonic nanobiocomposites with directly varied gold content were synthesized by a one-step redox method in water using a biocompatible polysaccharide κ-carrageenan (industrial product from algae) as both reducing and stabilizing matrix. The influence of the reactants ratio, temperature, and pH on the reaction was studied and the optimal reaction parameters were found. The structure and the properties of composite nanomaterials were examined in solid state and aqueous solutions by using complementary physical-chemical methods X-ray diffraction analysis, transmission electron microscopy, spectroscopy of electron paramagnetic resonance, atomic absorption and optical spectroscopy, polarimetry including optical rotatory dispersion with registration of interphase-crossbred Cotton effect of a chiral polysaccharide matrix on plasmonic chromophore of gold nanoparticles, dynamic and static light scattering. The new perspective multi-purpose nanocomposites demonstrate a complex of chiroplasmonic and magnetic properties, imparted by both nanoparticles and radicals enriched chiral polysaccharide matrix.