O. D. Hendrickson

Toxicity of nanosilver in intragastric studies: Biodistribution and metabolic effects

The unique physicochemical properties of silver nanoparticles explain their extensive application in consumer goods, food, and medicinal products. However, the biological effects of nanosilver after peroral exposure of mammals are still debatable. This study describes the biodistribution and biological action of 12nm non-coated silver nanoparticles intragastrically administered to male rats after acute (single exposure) and sub-acute (multiple exposures over 30 days) toxicity experiments. The daily doses were 2000 and 250mg/kg of body weight for single and multiple administrations, respectively. Silver tissue detection was conducted by elemental analysis with the help of atomic absorption spectroscopy. An estimation of the state of exposed animals was made and the dynamics of hematological and biochemical parameters of rats was studied. It was demonstrated that single and multiple administrations resulted in silver accumulation in the liver, kidneys, spleen, stomach, and small intestine. After both one- and repeated-dose exposures, the highest Ag contents were detected in the liver (0.87±0.37μg/g of organ) and kidneys (0.24±0.02μg/g of organ). The concentrations of silver detected in tissues were far smaller than the administered doses (<99%), indicating its efficient excretion from the organism. Acute and sub-acute exposures caused no animal mortality or signs of toxicity, manifested as changes in outward appearance or notable deviations in behavior or locomotor activity. Postmortem study revealed no visible pathomorphological abnormalities of internal organs. Hematological indices and biochemical parameters of the treated rats did not differ from those of the vehicle control animals. Overall, it can be concluded that nanosilver is able to be absorbed from the gastrointestinal tract into the bloodstream and accumulate in the secondary organs of rats. It showed no distinct toxicity under the experimental conditions of this study.

Methods of detection and identification of manufactured nanoparticles

The actual methods of detection and identification of manufactured nanoparticles in both simple and complex multi-component matrix for assessing biological effects and safety of nanotechnology products have been reviewed. The detection of priority species of biologically active nanoparticles, which include fullerenes, singleand multi-walled carbon nanotubes, nanoparticles of silver, gold, titanium oxide, aluminum, cerium, zinc and silicon, has been given a special attention. The requirements for sample preparation have been discussed. The results of the successful application for the detection of manufactured nanoparticles in biosamples with methods of scanning and transmission electron microscopy, confocal laser scanning microscopy, atomic force microscopy, scanning tunneling microscopy, size exclusion chromatography, field-flow fractionation, electrophoretic, light scattering, spectrophotometry, fluorescent spectroscopy, X-ray and other spectrometry, mass spectrometry, “particle counters”, immunochemistry have been reviewed. The possibilities and limitations of different techniques, and their complementarity have been analyzed.

Study of Distribution and Biological Effects of Fullerene C60 after Single and Multiple Intragastrical Administrations to Rats

In this study, male rats were intragastrically exposed to fullerene C60 for 1-day and 30-day periods at daily doses of 2000 and 250 mg/kg of body weight, respectively. Fullerene was detected in organs and tissues by HPLC after the extraction from biosamples with toluene. No statistically significant differences in hematological and biochemical parameters of control and treated rats were found after single and multiple administrations. Throughout the observation periods no lethality was observed. At necropsy, no pathomorphological changes in internal organs were recorded. Fullerene was found in stomach, small intestine, liver, lungs, spleen, kidneys, and blood. The amounts of the detected fullerene in comparison to the administered doses are far smaller which is the evidence of its efficient excretion. Hence, it can be assumed that fullerene nanoparticles penetrate from the gastrointestinal tract of rats into the bloodstream and translocate into secondary organs with no pronounced toxic effect in experimental conditions studied.

Development of Liposome Immune Lysis Assay for the Herbicide Atrazine

Abstract A homogeneous complement‐mediated liposome immune lysis assay (LILA) was developed for determination of the herbicide atrazine. To dispose the antigen on the surface of lipid bilayer the atrazine was conjugated to a dimirystoylphosphatidylethanolamine (DMPE) carrier. Calcein was compared with sulforhodamine 101 as a fluorophore label for entrapping into the antigen‐sensitized liposomes. The liposomes were incubated with rabbit anti‐atrazine antibodies in the presence of guinea pig complement. Formation of the antigen–antibody complexes on the liposomal surface initiated the lytic action of the complement. As free competing atrazine inhibited the lytic reaction, the amount of calcein released was inversely proportional to the atrazine content in the probe. Concentration and kinetic dependences of the immunoassay were characterized to reach its maximal sensitivity. The developed assay allows detecting atrazine in concentrations up to 0.13 ng mL−1 in the sample (0.04 ng mL−1 in the final reaction mixture). The named sensitivity is two orders higher than those for the microplate enzyme‐linked immunosorbent assay (ELISA) with the same antibodies which allows us to recommend LILA for environmental monitoring.

Experimental study and mathematical modeling of the interaction between antibodies and antigens on the surface of liposomes

Unilamellar liposomes with incorporated hapten-phospholipid conjugates were proposed as models of polyvalent antigens with migrating determinants for quantitative analysis of their interaction with antibodies. The monovalent pesticide atrazine was used as a model antigen. For its incorporation into the lipid bilayer, the atrazine carboxylated derivative was conjugated with dimyristoylphosphatidylethanolamine (DMPE). Unilamellar liposomes were prepared with dimyristoylphosphatidylcholine/atrazine-DMPE at molar ratios of 90:10, 95:5, 98:2, 99:1 and 99.5:0.5. Their interaction with the peroxidase-labeled anti-atrazine antibodies was studied by enzyme immunoassay and polarization fluoroimmunoassay techniques. It was shown that the increase in hapten content in the liposomes from 0.5 to 10 mol% led to an increase in the equilibrium constants of the interaction with antibodies from 0.093 x 10(8) to 0.303 x 10(8)M-1. The association rate constants varied from 1.45 x 10(5) to 15.5 x 10(5)M-1 s-1 depending on the antigen content in liposomes and experimental conditions. The measured constants were applied for a mathematical model describing multi-step interaction between antibodies and polyvalent liposomal antigens. The model adequately describes the quantitative regularities of the influence of antigen content and the affinity of immunochemical interaction on the quantity and the dynamics of the immune complexes forming.

Fullerenes: In vivo studies of biodistribution, toxicity, and biological action

The analysis of toxic effects of fullerenes and their derivatives towards mammals is presented in this review. The relationship between the biological activity of fullerenes and their physicochemical properties is characterized, as is the relationship between the outcomes of biosafety assessment of fullerenes and the exposure routes. To better enable evaluation of the toxic effect of nanomaterials in vivo standardized procedures both for experiments and for evaluation are recommended. Data on adsorption, distribution, metabolism, and excretion (ADME) of fullerenes for different routes of exposure is summarized. It is shown that fullerene absorption and translocation to tissues and organs distant from the deposition site depend on the exposure route and the dose administered. A detailed analysis is carried out of fullerene in vivo toxic effects following exposure via the respiratory system (inhalation and intratracheal administration), gastrointestinal tract (peroral and intraperitoneal administration), after dermal and parenteral (intraperitoneal, intravenous) administration. Fullerene inhalation causes local minor and short-term effects, and lung inflammation and pathological lesions are induced by high doses of nanoparticles. The literature data indicate also absence of skin and eye irritation, penetration into the derma and negligible sensitization for fullerene. No significant toxicity effects following the peroral exposure are observed and this is due to the low absorption of fullerene from the gastrointestinal tract and its effective excretion. The necessity to continue studying fullerene’s metabolic pathways and toxicity in acute and chronic experiments is reasoned.

Comparative Analysis of Models Describing Interactions between Antibodies and Liposomal Antigens

Mathematical models of three levels of complexity are proposed that describe the interactions between antibodies and polyvalent liposomal antigens. The models take into account the contribution of high-affinity bivalent complexes and clusters of several antigenic groups to the immunochemical reaction. The models were analyzed numerically at different values of thermodynamic and kinetic parameters of the antigen–antibody reaction. The conditions under which models of different levels of complexity provide a satisfactory description of the antigen–antibody interaction were determined. The adequacy of the results of modeling was confirmed experimentally in liposomal preparations differing from each other by the surface density of a monovalent hapten (atrazine) conjugated with a lipid.

Enzyme-linked lectinosorbent assay of Escherichia coli and Staphylococcus aureus

In this study, we developed a microplate sandwich analysis of Escherichia coli and Staphylococcus aureus bacterial pathogens based on the interaction of their cell wall carbohydrates with natural receptors called lectins. An immobilized lectin-cell-biotinylated lectin complex was formed in this assay. Here, we studied the binding specificity of several plant lectins to E. coli and S. aureus cells, and pairs characterized by high-affinity interactions were selected for the assay. Wheat germ agglutinin and Ricinus communis agglutinin were used to develop enzyme-linked lectinosorbent assays for E. coli and S. aureus cells with the detection limits of 4 × 106 and 5 × 105 cells/mL, respectively. Comparison of the enzyme-linked immonosorbent assay and the enzyme-linked lectinosorbent assay demonstrated no significant differences in detection limit values for E. coli. Due to the accessibility and universality of lectin reagents, the proposed approach is a promising tool for the control of a wide range of bacterial pathogens.

Development of microformat imaging microplate and membrane immunoenzyme assays of the herbicide atrazine

A microformat imaging technique in combination with registration of chemiluminescence by a charge-coupled device, CCD camera, were applied for the detection of the herbicide atrazine by two immunoenzyme assay formats – microplate and membrane assays. For the microplate (ELISA) case the detection limit was 95 pg mL−1, giving a 9.5-fold enhancement in comparison with a traditional colorimetric assay. The membrane dot blot assay allowed detection of up to 40 pg mL−1 of atrazine (4.5-fold enhancement). Due to the application of polyelectrolyte carriers for rapid reactants separation the membrane assay may be realized in 15 min. CCD-based registration of signals assures a high reproducibility of measurements; the variation coefficient is in the range 1–7%. The effectiveness of the assays developed for controlling triazine herbicides in mineral and tap water has been demonstrated.