G. V. Lisichkin

A versatile synthesis of highly bactericidal Myramistin® stabilized silver nanoparticles

Silver nanoparticles stabilized by a well-known antibacterial surfactant benzyldimethyl[3-(myristoylamino)propyl]ammonium chloride (Myramistin(®)) were produced for the first time by borohydride reduction of silver chloride sol in water. Stable aqueous dispersions of silver nanoparticles without evident precipitation for several months could be obtained. In vitro bactericidal tests showed that Myramistin(®) capped silver NPs exhibited notable activity against six different microorganisms-gram-positive and gram-negative bacteria, yeasts and fungi. The activity was up to 20 times higher (against E. coli) compared to Myramistin(®) at the same concentrations and on average 2 times higher if compared with citrate-stabilized NPs.

Formation of surface layers on silver nanoparticles in aqueous and water-organic media

Synthetic aspects of silver nanoparticle preparation in one-and two-phase aqueous and water-organic media and the influence of experimental factors on particle size and surface hydrophilicity/hydrophobicity are studied. It is shown that silver nanoparticles with controlled mean size and surface hydrophilic-hydrophobic properties can be obtained through direct synthesis or successive transformations.

Effect of detonation nanodiamonds on phagocyte activity.

Detonation ND (nanodiamond) holds much promise for biological studies and medical applications. Properties like size of particles, inclination for modification of their surface and unambiguous biocompatibility are crucial. Of prime importance is interaction between ND and immune cells, which supervise foreign intrusion into an organism and eliminate it. Neutrophils are more reactive in inflammatory response implementing cytotoxical arsenal including ROS (reactive oxygen species). The aim of the work was to estimate the ability of two ND samples (produced by Diamond Center and PlasmaChem) to keep the vitality of neutrophils from the inflammatory site. The ability of cells to generate ROS in the presence of ND particles is considered as indicating their biocompatibility. IR spectra and size of particles in the samples were characterized. Acid modification of ND was carried out to get the luminescent form. In the biological aspect, ND demonstrated up or down action, depending on the concentration, time and conditions of activation of cells. Weak action of ND in whole blood was obtained possibly owing to the ND adsorbed plasma proteins, which mask active functional groups to interact with the cell membrane. ND did not influence the viability of isolated inflammatory neutrophils in low and moderate concentrations and suppressed it in high concentrations (≥1 g/l). Addition of ND to the cell suspension initiated concentration‐dependent reaction to produce ROS similar to respiratory burst. ND up‐regulated response to bacterial formylpeptide, but up‐ and down‐modified (low or high concentrations, accordingly) response to such bacterial agents as OZ (opsonized zymosan), which neutrophils swallow up by oxygen‐dependent phagocytosis. Localization of the particles on the cell surface as into the cells was identified by monitoring the intrinsic fluorescence of oxidized ND. The various mechanisms that could account for penetration of ND particles into the cell are discussed. Common conclusion concerns compatibility of ND with living neutrophils from inflammatory site and their normal functioning for infection safeguard.

The structure of chemically modified detonation-synthesized nanodiamond particles

The results of studies of the structure of chemically modified detonation-synthesized nanodiamond (ND) particles by a set of physical and chemical methods are reported. It is shown that the crystal structure, size, and the paramagnetic properties of the particles persist during chemical modification processes. No nondiamond sp2 carbon is observed in the composition of the particles. The first experimental evidence for the uniform distribution of nitrogen impurities in the detonation-synthesized nanodiamond particles is presented.

Aggregative stability and polydispersity of silver nanoparticles prepared using two-phase aqueous organic systems

Synthetic aspects of obtaining silver organosols in two-phase aqueous organic systems and the influence of process conditions on the polydispersity and aggregative stability of obtained silver nanoparticles are considered.

Sensitized Fluorescence of Silver Nanoparticles in the Presence of Pyrene

The fluorescence of pyrene adsorbed onto the surface of the cetyltrimethylammonium-coated silver nanoparticles was studied. Pyrene molecules adsorbed on freshly prepared silver particles were found to be in close proximity to silver surface thus providing the possibility of energy transfer from excited pyrene to silver cores of the particles. In that case along with the expected fluorescence of pyrene we observed the fluorescence of the silver nanoparticles induced by the excited pyrene molecules. In due course the restructuring of the cetyltrimethylammonium layer resulted in moving of pyrene molecules away from silver surface and simultaneous disappearance of the silver nanoparticles fluorescence band. These data strongly support the recent hypothesis of fluorophore-plasmon coupled emission.

Synthesis and adsorption and luminescence properties of hydrophobic silver nanoparticles in the presence of pyrene

A procedure was developed for the synthesis of hydrophobic silver nanoparticles with an average size of 4 nm in two-phase water-organic emulsions. The physical properties of the obtained silver organosol were studied by molecular spectroscopy and electron microscopy. It was found that the synthesized silver nanoparticles had a specific surface of 60–110 m2/g. It was shown that chemically modified silver nanoparticles can be used as an adsorbent for preconcentrating polycyclic aromatic hydrocarbons (using pyrene as an example) from dilute n-hexane solutions followed by luminescence determination at room temperature.

Chemical modification of alumina and silica with alkylphosphonic acids and their esters

Alumina and silica were modified with alkylphosphonic acids and diethyl butylphosphonate. The boundaries of hydrolytic stability of the obtained surface-modified materials were determined.

Energy resources of the 21st century: problems and forecasts. Can renewable energy sources replace fossil fuels?

The state of the art and the major trends of development of world energy engineering are analyzed. It is concluded that throughout the 21st century the role of alternative sources will remain rather modest. Fossil fuel will still be the major source of energy until the end of the century. Because of depletion of accessible oil resources, the proportion of crude oil in the world energy balance will constantly decline, while the proportion of natural gas will grow. It is shown that energy production from any source, including alternative sources, cannot be environmentally benign if the scale of production is large. In the long term, humanity has no sources other than fusion energy, but transition to this source would not solve the problem of the planets heat balance.The bibliography includes 70 references.

Reactivity of a phosphonate layer grafted onto a surface of dispersed hydroxyapatite

The reactivity of a grafted layer contained on the surface of hydroxyapatite modified with diethyl butylphosphonate is studied. Modified hydroxyapatite is shown to interact with nucleophilic agents. The composition of reaction products depends on the nature of the latter.