Doxorubicin aqueous systems at low concentrations: Interconnection between self-organization, fluorescent and physicochemical properties, and action on hydrobionts.

Doxorubicin (Dox) is a highly effective cytostatic antibiotic that exhibits activity against a wide range of malignant neoplasms and is often used as the basis of various anti-tumor compositions. However, the use of Dox in therapeutic doses is associated with high systemic toxicity, which makes it urgent to find ways to reduce therapeutic concentrations, which is necessary primarily to minimize the side effects on the patient's body, as well as to reduce the harmful effects on aquatic ecosystems, commonly polluted by toxic pharmaceuticals. Studying the self-organization, physicochemical and spectral patterns, and their relation to bioeffects of Dox solutions in the range of low concentrations can reveal useful insights into the unknown effects of Dox as a cytostatic and potential pollutant of ecosystems. The self-organization in solutions and on substrates, physicochemical and spectral properties, and action of Dox solutions on hydrobionts were studied in the range of calculated concentrations from 1·10-20 to 1·10-4 M by methods of dynamic and electrophoretic light scattering (DLS and ELS), scanning electron microscopy (SEM), scanning probe microscopy (SPM), fluorescence spectroscopy, UV absorption spectroscopy, conductometry, tensiometry, pH-metry. Certified techniques for monitoring the toxicity of natural water and wastewater were used to establish the interconnection between these phenomena. It was shown that aqueous solutions of Dox are dispersed systems which rearrange their dispersed phase measuring hundreds of nm in size (nanoassociates) at dilution, followed by concerted changes in nanoassociates' parameters (size and ζ-potential) and properties of systems, as well as their bioassay results. SPM and SEM results confirm and complement the DLS and ELS data indicating the existence of nanoassociates in dilute Dox solutions.

L-Tryptophan Aqueous Systems at Low Concentrations: Interconnection between Self-Organization, Fluorescent and Physicochemical Properties, and Action on Hydrobionts.

As shown by fluorescence monitoring of dissolved organic matter, amino acid L-Trp can be present in natural water. The consequences of the presence of L-Trp at low concentrations in surface water systems are not yet established for hydrobionts. Studying the physicochemical patterns, as well as their relationships to the bioeffects of L-Trp solutions in the low concentration range, can provide new and important information regarding the unknown effects of L-Trp. The self-organization, physicochemical properties, fluorescence, UV absorption, and action of L-Trp solutions on Paramecium caudatum infusoria, Chlorella vulgaris algae were studied in the calculated concentrations range of 1 × 10-20-1 × 10-2 mol/L. The relationship between these phenomena was established using the certified procedures for monitoring the toxicity of natural water and wastewater. It was shown for the first time that aqueous solutions of L-Trp are dispersed systems in which the dispersed phase (nanoassociates) undergoes a rearrangement with dilution, accompanied by coherent changes in the nanoassociates' parameters and the properties of systems. The non-monotonic concentration dependence of fluorescence intensity (λex at 225 nm, λem at 340 nm) is in good agreement with the data on the nanoassociates' parameters, as well as with both the physicochemical properties of the systems and their bioassay results.

Diluted Aqueous Dispersed Systems of 4-Aminopyridine: The Relationship of Self-Organization, Physicochemical Properties, and Influence on the Electrical Characteristics of Neurons.

A variety of physicochemical methods were used to examine the self-organization, physicochemical, UV absorption, and fluorescent properties of diluted aqueous solutions (calculated concentrations from 1·10-20 to 1·10-2 M) of the membrane voltage-dependent potassium channels blocker 4-aminopyridine (4-AP). Using the dynamic light scattering method, it was shown that 4-AP solutions at concentrations in the range of 1·10-20-1·10-6 M are dispersed systems in which domains and nanoassociates of hundreds of nm in size are formed upon dilution. An interrelation between the non-monotonic concentration dependencies of the size of the dispersed phase, the fluorescence intensity (λ ex 225 nm, λ em 340 nm), specific electrical conductivity, and pH has been established. This allows us to predict the bioeffects of the 4-AP systems at low concentrations. The impact of these diluted aqueous systems on the electrical characteristics of identified neurons of Helix lucorum snails was studied. Incubation of neurons in the 4-AP systems for which the formation of domains and nanoassociates had been established lead to a nonmonotonic decrease of the resting potential by 7-13%. An analysis of the obtained results and published data allows for a conclusion that a consistent change in the nature and parameters of the dispersed phase, as well as the pH of the medium, apparently determines the nonmonotonic nature of the effect of the 4-AP systems in a 1·10-20-1·10-6 M concentration range on the resting membrane potential of neurons. It was found that the pre-incubation of neurons in the 4-AP system with a concentration of 1·10-12 M led to a 17.0% synergistic decrease in the membrane potential after a subsequent treatment with 1·10-2 M 4-AP solution. This finding demonstrates a significant modifying effect of self-organized dispersed systems of 4-AP in low concentrations on the neurons' sensitivity to 4-AP.

Diclofenac sodium aqueous systems at low concentrations: Interconnection between physicochemical properties and action on hydrobionts.

Diclofenac sodium (DS) is a widely used nonsteroidal anti-inflammatory drug (NSAIDs). NSAIDs are poorly removed during standard wastewater treatment. The consequences of the presence of NSAIDs in rivers and lakes at 10-11-10-8 mol/L are not yet established; therefore, ecotoxicologists have focused their efforts on studying the effect of low-concentration NSAIDs on fish and hydrobionts, and also on predicting the potential risks to humans. Literature provides some information about the bioeffects of some NSAID solutions in low concentrations but there is no physicochemical explanation for these phenomena. Studying the physicochemical patterns of DS solutions in the low range of concentrations and establishing an interconnection between the solutions' physicochemical properties and bioeffects can provide a conceptually new and important source of information regarding the unknown effects of DS. The physicochemical properties and action of DS solutions on Ceriodaphnia affinis cladocerans, Paramecium caudatum infusoria, Chlorella vulgaris unicellular green algae, as well as on the growth of the roots of Triticum vulgare wheat seeds, were studied in the calculated concentration range of 1 × 10-3-1 × 10-18 mol/L. The relationship between these phenomena was established using the certified procedures for monitoring the toxicity of natural water and wastewater. It was shown for the first time that water solutions of DS are dispersed systems in which the dispersed phase undergoes a rearrangement with dilution, accompanied by changes in its size and properties, which affects the nonmonotonic dependences of the system's physicochemical properties and could cause nonmonotonic changes in action on hydrobionts in the low concentration range.

Nanoassociate formation in highly diluted water solutions of potassium phenosan with and without permalloy shielding.

Diluted water solutions of anti-oxidant potassium phenosan, kept before explorations in "usual" conditions and in conditions of "permalloy container", i.e. shielding of solution from the influence of external low-frequency electromagnetic and/or geomagnetic fields, were studied. It is shown that in solutions kept in shielded conditions in the area of high dilution with a concentration of solutions lower than "threshold", nanoobjects called "nanoassociates", are not formed, and anomalous physicochemical and biological properties observed in solutions kept in "usual" conditions, are not found. We conclude that anomalous physicochemical and biological properties of highly diluted water solutions of potassium phenosan made under "usual" conditions are determined by "nanoassociates", in which an external low-frequency electromagnetic and/or geomagnetic field is a necessary condition of the formation.

Sterol binding by methyl-ß-cyclodextrin and nystatin--comparative analysis of biochemical and physiological consequences for plants.

The dependence of membrane function on its sterol component has been intensively studied with model lipids and isolated animal membranes, but to a much lesser extent with plant membranes. Depleting membrane sterols could be predicted to have a strong effect on membrane activity and have harmful physiological consequences. In this study, we characterized membrane lipid composition, membrane permeability for ions, some physiological parameters, such as H2O2 accumulation, formation of autophagosomal vacuoles, and expression of peroxidase and autophagic genes, and cell viability in the roots of wheat (Triticum aestivum L.) seedlings in the presence of two agents that specifically bind to endogenous sterols. The polyene antibiotic nystatin binds to endogenous sterols, forming so-called 'nystatin pores' or 'channels' in the membrane, and methyl-ß-cyclodextrin has the capacity to sequester sterols in its hydrophobic core. Unexpectedly, although application of both methyl-ß-cyclodextrin and nystatin reduced the sterol content, their effects on membrane permeability, oxidative status and autophagosome formation in roots differed dramatically. For comparison, we also tested the effects of the antibiotic gramicidin S, which does not bind to sterols but forms nonspecific channels in the membrane. Gramicidin S considerably increased membrane permeability, caused oxidative stress, and reduced cell viability. Our results suggest that a decrease in the sterol content is, in itself, not sufficient to have deleterious effects on a cell. The disturbance of membrane integrity, rather than the decrease in the sterol content, is responsible for the toxicity of sterol-binding compounds.

Effects of sterol-binding agent nystatin on wheat roots: the changes in membrane permeability, sterols and glycoceramides.

Plant sterols are important multifunctional lipids, which are involved in determining membrane properties. Biophysical characteristics of model lipid and isolated animal membranes with altered sterol component have been intensively studied. In plants however, the precise mechanisms of involvement of sterols in membrane functioning remain unclear. In present work the possible interactions between sterols and other membrane lipids in plant cells were studied. A useful experimental approach for elucidating the roles of sterols in membrane activity is to use agents that specifically bind with endogenous sterols, for example the antibiotic nystatin. Membrane characteristics and the composition of membrane lipids in the roots of wheat (Triticum aestivum L.) seedlings treated with nystatin were analyzed. The application of nystatin greatly increased the permeability of the plasma membrane for ions and SH-containing molecules and decreased the total sterol level mainly as a consequence of a reduction in the amount of ß-sitosterol and campesterol. Dynamic light-scattering was used to confirm the in vitro formation of stable complexes between nystatin and ß-sitosterol or cholesterol. Sterol depletion was accompanied by a significant rise in total glycoceramide (GlCer) content after 2h treatment with nystatin. Analysis of the GlCer composition using mass spectrometry with electrospray ionization demonstrated that nystatin induced changes in the ratio of molecular species of GlCer. Our results suggest that changes in the sphingolipid composition can contribute to the changes in plasma membrane functioning induced by sterol depletion.