No abstract

A novel procedure for the synthesis of polyethylenimine (PEI)−silica nanocomposite particles with high adsorption capacities has been developed based on an emulsion templating concept. The exceptional chelating properties of PEI as the parent polymer for the particle core promote the binding abilities of the resulting composite for charged species. Further, the subsequent introduction of silica via the self-catalyzed hydrolysis of tetraethoxysilane facilitates production of robust composite particles with smooth surfaces, enabling potential use in multiphase environments. To enable tailored application in solid/liquid porous environments, the production of particles with reduced sizes was attempted by modulating the shear rates and surfactant concentrations during emulsification. The use of high-speed homogenization resulted in a substantial decrease in average particle size, while increasing surfactant loading only had a limited effect. All types of nanocomposites produced demonstrated excellent binding capacities for copper ions as a test solute. The maximum binding capacities of the PEI−silica nanocomposites of 210−250 mg/g are comparable to or exceed those of other copper binding materials, opening up great application potential in resources, chemical processing, and remediation industries.

The lipid peroxidation process in hemocytes, activities of phenoloxidase and key enzymatic antioxidants (superoxide dismutase, glutathione-S-transferase, catalase) and nonenzymatic antioxidants (thiols, ascorbate) in hemolymph of the greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) were studied during the encapsulation process of nylon implants. It has been established that as soon as 15 min after piercing a cuticle with the implant, a capsule is formed on its surface. Active melanization of the capsule has been shown to last for 4 h. During the first hours after incorporating the implant, an increase in phenoloxidase activity and lipid peroxidation in the insect hemocytes has been revealed. Adhesion and degranulation on the surface of foreign object lead to the depletion of total hemocytes count (THC). Our results indicated that thiols and ascorbate molecules take part in the immediate antioxidant response, during later stages of encapsulation process hemolymph glutathione-S-transferase detoxifies and protects insect organism thereby restoring the internal redox balance. We suggest that nonenzymatic and enzymatic antioxidants of hemolymph plasma play a key role in the maintenance of redox balance during encapsulation of foreign targets.

Increasing demand for copper resources, accompanied by increasing pollution, has resulted in an urgent need for effective materials for copper binding and extraction. Polyethylenimine (PEI) is one of the strongest copper-chelating agents but is not suitable directly (as is) for most applications due to its high solubility in water. PEI-based composite materials show potential as efficient and practical alternatives. In the present work, the interaction of copper ions with PEI−silica nanocomposite particles and precursor PEI microgels (as a reference) is investigated. It is hypothesized that the main driving force of the reaction is chelation of copper ions by amino groups in the PEI network. The presence of silica in the PEI−silica composites was shown to increase the copperbinding capacity in comparison with the parent microgel. The copper-binding behavior of etched (PEI-free "ghost") composite particles in comparison with the original composites and microgel particles shows that silica nanoparticles in the composite structure increase the number of copper-binding sites in the PEI network rather than adsorbing copper themselves. PEI−silica composites can be easily recycled after copper adsorption by simply washing in 1 M nitric acid, which results in complete copper extraction. Employing this recovery method, PEI−silica composite particles can be used for multiple, efficient cycles of copper removal and extraction.

Ectoparasitoids inject venom into hemolymph during oviposition. We determined the influence of envenomation by the parasitoid, Habrobracon hebetor, on the hemocytes of its larval host, Galleria mellonella. An increase in both intracellular Са(2+) content and phospholipase C activity of the host hemocytes was recorded during 2 days following envenomation by the parasitoid. The decreased hemocyte viability was detected 1, 2, and 24 h after the envenomation. Injecting of the crude venom (final protein concentration 3 μg/ml) into the G. mellonella larvae led to the reduced hemocyte adhesion. The larval envenomation caused a decrease in transmembrane potential of the hemocytes. These findings document the suppression of hemocytic immune effectors in the parasitized host larvae.

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The method for measurement of trans-membrane potential of cell membrane was evaluated for the case of low potential value using fluorescence probe 4-(4-dimethylaminostyryl)-1-methylpyridinium, DSM. The method is based on comparative titration of cells with probe in buffers containing Na(+) or K(+). The apparent trans-membrane potential obtained with this way is a result of K(+)-Na(+) pump activity. The presented approach allowed measuring the low value of potential with 1-2 mV of accuracy without additional calibration procedures. The method was applied for investigation of potential of cell membrane of haemocytes of Galleria mellonella larvae. The value of potential of intact insect's haemocytes was found in the range from -10 to -20 mV. The change of potential value of haemocytes was investigated under model immune response and natural envenomation and parasitizing. The obtained deviations of cell membrane potential were in good correlation with changes of activity of main immune reactions, described in literature and obtained by us earlier.

Design of micro/nanoadsorbents developed for effective copper extraction should consider methods of their retrieval from relevant copper-rich environments, which are commonly complex multiphase mixtures, such as slurries of polluted soils and sediments, copper minerals including lowgrade ores, and industrial and mining wastes. This work reports integration of copper-chelating polyethylenimine (PEI) with a robust silica network and highly magnetic magnetite nanoparticles, resulting in magnetic PEI−silica nanocomposite microparticles that enable efficient binding of copper ions in both aqueous solutions and complex, multiphase mixtures with subsequent retrieval using magnetic force. Produced via simple emulsion templating, these nanocomposite particles can withstand highly acidic conditions and multiple copper extraction cycles, without loss of efficiency after five consecutive cycles of copper extraction. PEI−silica−magnetic nanoparticles composites effectively bind all copper ions leached into an aqueous phase and allow their rapid magnetically induced separation from aqueous solutions and mixtures of both coarse and fine solid particles, demonstrating promising results for progress toward more sustainable copper extraction techniques.