Larisa Yu. Matora

Analytical and Theranostic Applications of Gold Nanoparticles and Multifunctional Nanocomposites

Gold nanoparticles (GNPs) and GNP-based multifunctional nanocomposites are the subject of intensive studies and biomedical applications. This minireview summarizes our recent efforts in analytical and theranostic applications of engineered GNPs and nanocomposites by using plasmonic properties of GNPs and various optical techniques. Specifically, we consider analytical biosensing; visualization and bioimaging of bacterial, mammalian, and plant cells; photodynamic treatment of pathogenic bacteria; and photothermal therapy of xenografted tumors. In addition to recently published reports, we discuss new data on dot immunoassay diagnostics of mycobacteria, multiplexed immunoelectron microscopy analysis of Azospirillum brasilense, materno-embryonic transfer of GNPs in pregnant rats, and combined photodynamic and photothermal treatment of rat xenografted tumors with gold nanorods covered by a mesoporous silica shell doped with hematoporphyrin.

Multiplexed dot immunoassay using Ag nanocubes, Au/Ag alloy nanoparticles, and Au/Ag nanocages

AbstractWe report the first application of Ag nanocubes, Au/Ag alloy nanoparticles, and Au/Ag nanocages in a multiplexed dot immunoassay. The assay principle is based on the staining of analyte drops on a nitrocellulose membrane strip by using multicolor nanoparticles conjugated with biospecific probing molecules. Nanoparticles were prepared by a galvanic replacement reaction between the Ag atoms of silver nanocubes and Au ions of tetrachloroauric acid. Depending on the Ag/Au conversion ratio, the particle plasmon resonance was tuned from 450 to 700 nm and the suspension color changed from yellow to blue. The particles of yellow, red, and blue suspensions were functionalized with chicken, rat, and mouse immuno gamma globulin (IgG) molecular probes, respectively. The multiplex capability of the assay was illustrated by a proof-of-concept experiment involving simultaneous one-step determination of target molecules (rabbit anti-chicken, anti-rat, and anti-mouse antibodies) with a mixture of fabricated conjugates. Under naked eye examination, no cross-colored spots or nonspecific bioconjugate adsorption were observed, and the low detection limit was about 20 fmol.

Identification of an O-linked repetitive glycan chain of the polar flagellum flagellin of Azospirillum brasilense Sp7.

This is the first report to have identified an O-linked repetitive glycan in bacterial flagellin, a structural protein of the flagellum. Studies by sugar analysis, Smith degradation, (1)H and (13)C NMR spectroscopy, and mass spectrometry showed that the glycan chains of the polar flagellum flagellin of the plant-growth-promoting rhizobacterium Azospirillum brasilense Sp7 are represented by a polysaccharide with a molecular mass of 7.7 kDa, which has a branched tetrasaccharide repeating unit of the following structure:

Biofilm Formation by Paenibacillus polymyxa Strains Differing in the Production and Rheological Properties of Their Exopolysaccharides

We evaluated the ability of several strains of the rhizobacterium Paenibacillus polymyxa, differing in the yield and rheological properties of their exopolysaccharides, to form biofilms on abiotic surfaces. Of these strains, P. polymyxa 1465, giving the highest yield of extracellular polysaccharides and the highest kinematic viscosity of the culture liquid and of aqueous polysaccharide solutions, proved to be the most active in forming biofilms on hydrophobic and hydrophilic surfaces. Enzyme-linked immunosorbent assay with rabbit polyclonal antibodies developed to isolated exopolysaccharides of P. polymyxa 1465 and 92 was used to detect P. polymyxa’s polysaccharidic determinants in the composition of the biofilm materials.

Rhizosphere indole-3-acetic acid as a mediator in the Sorghum bicolor-phenanthrene-Sinorhizobium meliloti interactions.

We studied a model system consisting of Sorghum bicolor, phenanthrene, and an auxin-producing polycyclic aromatic hydrocarbon-degrading Sinorhizobium meliloti strain to clarify whether rhizosphere indole-3-acetic acid (IAA) takes part in the plant-pollutant-bacteria interactions. Phenanthrene and S. meliloti treatments of sorghum contributed to a decrease in the rhizosphere IAA concentration and to phytohormone accumulation, respectively. Regression analysis showed significant correlations between alteration in root-zone IAA content and alterations in the root-surface area, exudation, and rhizosphere effects for culturable heterotrophic bacteria, the S. meliloti strain, and other phenanthrene degraders. According to the data obtained, phenanthrene degraders get an advantage over nondegradative rhizobacteria from IAA for rhizosphere colonization. An IAA-dependent increase in the root-surface area leads to improved sorghum growth under pollutant stress. The carbon flux from the roots is corrected by the auxin because of its influence on the exuding-surface area and on the intensity of secretion by the root cells. On the other hand, the rhizosphere IAA pool may be plant-regulated by means of alteration in carboxylate exudation and its influence on bacterial auxin production. A scenario for the IAA-mediated S. bicolor-phenanthrene-S. meliloti interactions is proposed.

Use of colloidal gold to obtain antibiotin antibodies

A method has been developed for obtaining antibiotin antibodies by the use of colloidal gold particles as carrier. The antibodies possessed sensitivity exceeding that of streptavidin as demonstrated by dot-blot analysis in a model system.

Use of ELISA with Antiexopolysaccharide Antibodies to Evaluate Wheat-Root Colonization by the Rhizobacterium Paenibacillus polymyxa

Enzyme-linked immunosorbent assay with rabbit polyclonal antibodies developed to isolated exopolysaccharide of Paenibacillus polymyxa 1465 was used to evaluate the colonization of wheat-seedling roots by this bacterium. The assay conditions were optimized for detection of the P. polymyxa exopolysaccharide determinants forming part of the samples used (homogenates of inoculated roots). The dynamics of the immunoenzymatic revealing of specific polysaccharidic antigenic determinants in the samples’ composition correlated with an increase in P. polymyxa numbers on the roots found by estimation of colony-forming units.

Signal effects of the lectin from the associative nitrogen-fixing bacterium Azospirillum brasilense Sp7 in bacterial–plant root interactions

Background and aimsAzospirillum brasilense, which has the potential to stimulate plant growth, belongs to the group of plant growth-promoting bacteria. The lectin found on the surface of A. brasilense strain Sp7 has the ability to bind specific carbohydrates and ensures adhesion of the bacteria to the root surface. The aim of this work was to investigate possible inductive effects of the Sp7 lectin on the plant cell signal systems.MethodsEnzyme-linked immunosorbent assay, spectrophotometry, and thin-layer and gas–liquid chromatography were used to determine the content of signal intermediates in the cells of wheat root seedlings. Laser scanning confocal microscopy was used to examine the localization of fluorescently labeled lectin on the plant cell.ResultsThe Sp7 lectin acted on the signal system components in wheat seedling roots by regulating the contents of cAMP, nitric oxide, diacylglycerol, and salicylic acid, as well as by modifying the activities of superoxide dismutase and lipoxygenase. The revealed cell membrane localization of the lectin is of deciding importance for its signal function.ConclusionsThe results of the study suggest that the A. brasilense Sp7 lectin acts as a signal molecule involved in the interaction of growth-promoting rhizobacteria with plant roots.

Immunological Properties of Azospirillum Cell Surface: the Structure of Carbohydrate Antigens and Evaluation of their Involvement in Bacteria-Plant Contact Interactions

Immunization of rabbits with glutar aldehyde-treated intact Azospirillum cells results in the production of antibodies specific mainly with regard to the cell O-antigens. EPS, CPS, and O-specific polysaccharides of A. brasilense Sp 7 are antigenically identical. Pre-treatment of the wheat seedling roots and a carrot cell suspension with LPS of strain Sp 245 promotes significantly bacterial adhesion to wheat roots and Azospirillum-induced agglutination of carrot cells. It also leads to an increased synthesis of the major proteins in the wheat root apoplast, which is comparable with the plant response to inoculation with whole cells. This may be explained by an active effect of Azospirillum LPS on the receptor systems of plant cells.

Electro-optical study of the exposure of Azospirillum brasilense carbohydrate epitopes.

The exposure of Azospirillum brasilense carbohydrate epitopes was investigated by electro-optical analysis of bacterial cell suspensions. To study changes in the electro-optical (EO) properties of the suspensions, we used antibodies generated to the complete lipopolysaccharide of A. brasilense type strain Sp7 and also antibodies to the smooth and rough O polysaccharides of Sp7. After 18 hr of culture growth, the EO signal of the suspension treated with antibodies to smooth O polysaccharide was approximately 20% lower than that of the suspension treated with antibodies to complete lipopolysaccharide (control). After 72 hr of culture growth, the strongest EO signal was observed for the cells treated with antibodies to rough O polysaccharide (approximately 46% greater than the control), whereas for the cells treated with antibodies to smooth O polysaccharide, it was much lower (approximately 23% of the control). These data were confirmed by electron microscopy. The results of the study may have importance for the rapid evaluation of changes in lipopolysaccharide form in microbial biotechnology, when the antigenic composition of the bacterial surface requires close control.