Copper-Containing Bionanocomposites Based on Natural Raw Arabinogalactan as Effective Vegetation Stimulators and Agents against Phytopathogens.

Novel copper-containing bionanocomposites based on the natural raw arabinogalactan have been obtained as universal effective agents against phytopathogen Clavibacter sepedonicus and development stimulants of agricultural plants. Thus, the use of such nanosystems offers a solution to the tasks set in biotechnology while maintaining high environmental standards using non-toxic, biocompatible, and biodegradable natural biopolymers. The physicochemical characteristics of nanocomposites were determined using a number of analytical methods (elemental analysis, transmission electron microscopy and spectroscopic parameters of electron paramagnetic resonance, UV-visible, etc.). The results of the study under the influence of the nanocomposites on the germination of soybean seeds (Glycine max L.) and the vegetation of potatoes (Solanum tuberosum L.) showed the best results in terms of biometric indicators. It is especially worth noting the pronounced influence of the nanocomposite on the development of the root system, and the increase in the mass of the potato root system reached 19%. It is also worth noting that the nanocomposites showed a stimulating effect on the antioxidant system and did not have a negative effect on the content of pigments in potato tissues. Moreover, the resulting bionanocomposite showed a pronounced antibacterial effect against the phytopathogenic bacterium. During the co-incubation of phytopathogen Clavibacter sepedonicus in the presence of the nanocomposite, the number of cells in the bacterial suspension decreased by up to 40% compared to that in the control, and a 10% decrease in the dehydrogenase activity of cells was also detected.

Spontaneous Transformation of Biomedical Polymeric Silver Salt into a Nanocomposite: Physical-Chemical and Antimicrobial Properties Dramatically Depend on the Initial Preparation State.

An antimicrobial polyacrylic silver salt (freshly prepared, stored for one year and model-aged) was studied by physical-chemical techniques for nanoparticle detection. In all cases, this salt represents a composite of radical-enriched macromolecules and silver(0) nanoparticles. As time passed, the initial small spherical nanoparticles were converted into larger non-spherical silver nanoparticles. The initial highly water-soluble antimicrobial solid nanocomposite almost loses its solubility in water and cannot be used as an antimicrobial agent. Unlike insoluble solid silver polyacrylate, its freshly prepared aqueous solution retains a liquid-phase consistency after one year as well as pronounced antimicrobial properties. The mechanism of these spontaneous and model-simulated processes was proposed. These results have attracted attention for officinal biomedicinal silver salts as complex radical-enriched nanocomposite substances; they also indicate contrasting effects of silver polymeric salt storing in solid and solution forms that dramatically influence antimicrobial activity.

Effect of Natural Polysaccharide Matrix-Based Selenium Nanocomposites on Phytophthora cactorum and Rhizospheric Microorganisms.

We studied the effects of new chemically synthesized selenium (Se) nanocomposites (NCs) based on natural polysaccharide matrices arabinogalactan (AG), starch (ST), and kappa-carrageenan (CAR) on the viability of phytopathogen Phytophthora cactorum, rhizospheric bacteria, and potato productivity in the field experiment. Using transmission electron microscopy (TEM), it was shown that the nanocomposites contained nanoparticles varying from 20 to 180 nm in size depending on the type of NC. All three investigated NCs had a fungicidal effect even at the lowest tested concentrations of 50 µg/mL for Se/AG NC (3 µg/mL Se), 35 µg/mL for Se/ST NC (0.5 µg/mL Se), and 39 µg/mL for Se/CAR NC (1.4 µg/mL Se), including concentration of 0.000625% Se (6.25 µg/mL) in the final suspension, which was used to study Se NC effects on bacterial growth of the three common rhizospheric bacteria Acinetobacter guillouiae, Rhodococcus erythropolis and Pseudomonas oryzihabitans isolated from the rhizosphere of plants growing in the Irkutsk Region, Russia. The AG-based Se NC (Se/AG NC) and CAR-based Se NC (Se/CAR NC) exhibited the greatest inhibition of fungal growth up to 60% (at 300 µg/mL) and 49% (at 234 µg/mL), respectively. The safe use of Se NCs against phytopathogens requires them to be environmentally friendly without negative effects on rhizospheric microorganisms. The same concentration of 0.000625% Se (6.25 µg/mL) in the final suspension of all three Se NCs (which corresponds to 105.57 µg/mL for Se/AG NC, 428.08 µg/mL for Se/ST NC and 170.30 µg/mL for Se/CAR NC) was used to study their effect on bacterial growth (bactericidal, bacteriostatic, and biofilm formation effects) of the three rhizospheric bacteria. Based on our earlier studies this concentration had an antibacterial effect against the phytopathogenic bacterium Clavibacter sepedonicus that causes diseases of potato ring rot, but did not negatively affect the viability of potato plants at this concentration. In this study, using this concentration no bacteriostatic and bactericidal activity of all three Se NCs were found against Rhodococcus erythropolis based on the optical density of a bacterial suspension, agar diffusion, and intensity of biofilm formation, but Se/CAR and Se/AG NCs inhibited the growth of Pseudomonas oryzihabitans. The cell growth was decrease by 15-30% during the entire observation period, but the stimulation of biofilm formation by this bacterium was observed for Se/CAR NC. Se/AG NC also had bacteriostatic and antibiofilm effects on the rhizospheric bacterium Acinetobacter guillouiae. There was a 2.5-fold decrease in bacterial growth and a 30% decrease in biofilm formation, but Se/CAR NC stimulated the growth of A. guillouiae. According to the results of the preliminary field test, an increase in potato productivity by an average of 30% was revealed after the pre-planting treatment of tubers by spraying them with Se/AG and Se/CAR NCs with the same concentration of Se of 0.000625% (6.25 µg/mL) in a final suspension. The obtained and previously published results on the positive effect of natural matrix-based Se NCs on plants open up prospects for further investigation of their effects on rhizosphere bacteria and resistance of cultivated plants to stress factors.

Selenium Nanocomposites in Natural Matrices as Potato Recovery Agent.

The paper presents a study of the effect of chemically synthesized selenium nanocomposites (Se NCs) in natural polymer matrices arabinogalactan (AG) and starch (ST) on the viability of the potato ring rot pathogen Clavibacter sepedonicus (Cms), potato plants in vitro, and the soil bacterium Rhodococcus erythropolis. It was found that the studied Se NCs have an antibacterial effect against the phytopathogenic Cms, reducing its growth rate and ability to form biofilms. It was revealed that Se NC based on AG (Se/AG NC) stimulated the growth and development of potato plants in vitro as well as their root formation. At the same time, Se did not accumulate in potato tissues after the treatment of plants with Se NCs. The safety of the Se NCs was also confirmed by the absence of a negative effect on the growth and biofilm formation of the soil bacterium R. erythropolis. The obtained results indicate that Se NCs are promising environmentally safe agents for the protection and recovery of cultivated plants from phytopathogenic bacteria.

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.

Colloidal aggregates of Pd nanoparticles supported by larch arabinogalactan.

Palladium nanoparticles (PdNPs) are used in catalysis, hydrogen storage, biomedicine, and so on. Arranging the self-assembly of PdNPs within colloidal aggregates is desirable for improving their consumer properties. Stable widely dispersed colloidal aggregates of larch arabinogalactan (LARB) containing nanosized (5-nm) PdNPs were obtained by reducing Pd ions in alkaline solutions of LARB. Centrifugation resulted in a set of LARB-PdNP colloids ranging from 60 to 240 nm. The colloids were studied by static light scattering (SLS) and dynamic light scattering (DLS). The SLS data presented as Kratki plots correspond to a particle scattering factor of linear rather than branched chains. The fractal dimension of the LARB-PdNP colloids was found by SLS to be d = 1.96, which is between the values for diffusion- and reaction-limited aggregation. This result is ascribed to the aggregate's internal motion, which is evident from the power-law exponent of the dependence of the DLS relaxation rate on the scattering vector, <Γ> ~ q(α) with α = 2.24. The structure-sensitive ratio of the radius of gyration to the hydrodynamic radius was found to vary within the interval of 0.8 ≤ R(g)/R(h) ≤ 1.2 corresponding, to the spherical form of LARB-PdNP colloids. A spiderweblike PdNP distribution pattern was observed by transmission electron microscopy. Insertion of PdNPs did not affect the fractal dimension, the power-law exponent α, or the architecture of the pristine LARB aggregates in water. The red shift of the surface plasmon extinction observed with increasing LARB-PdNP colloidal size indicates the collective optical response of the PdNP ensemble in the colloid.

Bactericidal action of Ag(0)-antithrombotic sulfated arabinogalactan nanocomposite: coevolution of initial nanocomposite and living microbial cell to a novel nonliving nanocomposite.

The first step of the interaction between Ag(0) nanocomposite with antiatherogenic anticoagulant sulfated arabinogalactan involves the transportation and concentration of antimicrobial nanosilver in the bacteria target (E. coli). Further, the silver ions in dynamic equilibrium with metal backbone of the nanoparticles (NPs) reach the membrane surface and bond with this surface. Simultaneously, the redox interaction of silver cations with main reducing components of the membrane surface is triggered to afford the zero-valence silver atoms that are stabilized to form metal clusters, or new NPs of silver. Size and morphology of these NPs are defined by specific conditions of their synthesis involving the microorganism membrane: The Ag(0) NPs formed on membranes and fragments of the destroyed bacteria have other morphology (including triangular) and smaller sizes in comparison with the initial nanocomposite that additionally enhances antimicrobial activity of such NPs. FROM THE CLINICAL EDITOR: This study investigates silver nanocompistes (Ag(0) NPs) and their interaction with antiatherogenic anticoagulant sulfated arabinogalactan. A complex set of interactions are described, leading to Ag(0)NPs formed on membranes and fragments of destroyed bacteria demonstrating altered morphology and smaller sizes in comparison with the initial nanocomposite that additionally enhances antimicrobial activity of such NPs.