Elena K. Volkova

Synthesis of magnetite hydrosols and assessment of their impact on living systems at the cellular and tissue levels using MRI and morphological investigation

MRI and morphological investigations into internal organ tissues and tumors in rats with liver cancer PC-1 under the intraperitoneal administration of magnetite hydrosols have been performed. The absence of any toxic effect of magnetite nanoparticles at low concentrations (0.325 mg/mL) has been determined using neutrophil granulocytes. A technique for the synthesis of citrate-stabilized magnetite hydrosols by the coprecipitation of Fe2+ and Fe3+ salts is described. Their electrokinetic potential is −32 ± 2 mV at pH 6.5 ± 0.1. The size distribution of magnetite nanoparticles is obtained by dynamic light scattering. The average size of magnetite nanoparticles is 23 ± 6 nm. The absorption spectra of magnetite hydrosols have been measured. The dependence of the optical density on the concentration has also been obtained. Molar absorption coefficients of magnetite nanoparticles have been calculated at the following wavelengths: 532, 633, 660, and 785 nm.

Synthesis, surface morphology, and optical and structural properties of CdS and ZnS nanoparticles

Synthesis of CdS and ZnS nanoparticles in reverse micelles and organic solvents has been carried out. Particles with a hexagonal structure 2–5 nm in size are formed during synthesis. Maintaining the reaction mixture at room temperature leads to the formation of nanoparticles with a cubic structure 100–150 nm in size. The changes in the optical properties of CdS and ZnS nanoparticles, depending on the synthesis method and conditions and on the precursors used, have been investigated. The luminescence characteristics of local surface defects of nanoparticles depend weakly on nanoparticle sizes. The dependence of the fluorescence and phosphorescence intensity of nanoparticle surface defects on the polarity of surrounding solution is demonstrated; thus, these particles can be used as polarity indicators.

Fluorescent ZnCdS nanoparticles for glucose sensing

Abstract. The effect of glucose on fluorescence of synthesized ZnCdS nanoparticles in the presence of glucose oxidase or in a mixture of glucose oxidase and peroxidase has been investigated. Behavior of fluorescence characteristics of ZnCdS nanoparticles with nonstabilized surface and coated with polymer shell is compared. It has been shown that, for uncoated ZnCdS nanoparticles, hydrogen peroxide formed by glucose oxidation with glucose oxidase causes static quenching of the nanoparticle fluorescence. A quenching mechanism is proposed in which surface centers of fluorescence, which include cationic vacancies, trap oxygen ions supplied by hydrogen peroxide. It has been shown that the linear Stern–Volmer plot has no threshold within the investigated concentrations of glucose. The sensitivity of ZnCdS nanoparticles to glucose, determined from the slope of linear Stern–Volmer plot, is maximum for polymer-coated nanoparticles and is 12.2  ml/mg. With peroxidase, there is a threshold concentration of glucose (160 μM) below which the nanoparticles become insensitive to glucose.

ZnCdS nanoparticles as nanobiosensors to determine denaturation of tissue

The temperature dependence of the fluorescent spectra of ZnCdS nanoparticles placed into a biological tissue has been investigated. It is shown that the fluorescence peak of the nanoparticles is shifted towards longer wavelengths, and fluorescence quenching is observed during heating the biological tissue until its denaturation. ZnCdS nanoparticles are suitable for measuring the temperature of biological nanoobjects under photothermolysis.

Temperature dependence of the fluorescence spectrum of ZnCdS nanoparticles

The temperature sensitivity of the spectral characteristics of ZnCdS nanoparticles both stabilized and coated with polyacrylic acid is compared. It is shown that the luminescence of the nanoparticles has two temperature-dependent parameters, namely, the intensity and the peak position. Variations in these parameters are due to the distortion of the energy states of luminescent surface defects. Aggregation of the nanoparticles does not distort obtained dependencies. Temperature sensitivity is higher for the nanoparticles coated with a layer of polyacrylic acid.

Glucose and temperature sensitive luminescence ZnCdS nanoparticles

The effect of glucose on fluorescence characteristics of synthesized ZnCdS nanoparticles in glucose oxidase solution has been investigated. It has been shown that, on addition of glucose, the nanoparticle fluorescence is quenched. Dynamics of fluorescence quenching with increasing glucose concentration was observed. Threshold sensitivity of recording of glucose concentration has been 0,25 mg/ml. So the presented effect opens the facilities for application of synthesized ZnCdS nanoparticles for the glucose control in bodyfluids.

Optical characteristics of cadmium sulfide nanoparticles synthesized in polyethylene matrix and ortho -xylene solution

The properties of CdS nanoparticles synthesized in a polyethylene matrix and an ortho-xylene solution are compared. It is shown that these nanoparticles have different shapes, structures, and degrees of imperfection. Due to these differences, unaggregated nanoparticles in solution exhibit luminescence in contrast to nanoparticles in polyethylene. The stabilization of nanoparticles in polyethylene most probably occurs via OH groups, while nanoparticles in solution are stabilized due to partial interaction with dissolved sulfur. The absorption and luminescence spectra of samples with polyethylene are strongly distorted by reabsorption and scattering, while this effect in solution is absent due to a small concentration of nanoparticles.

Ecophotonics: assessment of temperature gradient in aquatic organisms using up-conversion luminescent particles

In the frameworks of developing ecophotonics, we consider the possibility of applying luminescence spectroscopy for monitoring conditions of aquatic organisms, aimed at the study and prognosis of the effect of human activity and climate changes on the environment. The method of luminescence spectroscopy in combination with anti-Stokes luminophores (up-conversion particles) used as optical sensors is used for the noninvasive assessment of the temperature gradient in the internal tissues of aquatic organisms. It is shown that the temperature dependence of the intensity ratio observed in the maxima of the luminescence spectrum bands of the particles Y2O3 : Yb, Er, administered in a biological object, is linear. This fact offers a possibility of using the up-conversion particles for assessing the metabolic activity of different tissues, including those in the framework of ecological monitoring.

Fluorescent ZnCdS nanoparticles for nanothermometry of biological tissues

Internal temperature of biological tissues was measured in real-time mode under close-to-in-vivo conditions. Research technique is based on the comparison of the temperature inside the biological object and changes in the fluorescence spectra of temperature-sensitive fluorescent semiconductor ZnCdS nanoparticles introduced into muscle tissue. The temperature dependence of the ratio of maximum fluorescence intensities of the nanoparticles and the biological tissue was approximately linear.

Comparison of temperature sensing of the luminescent upconversion and ZnCdS nanoparticles

The luminescence spectra of upconversion nanoparticles (UCNPs) and ZnCdS nanoparticles (ZnCdSNPs) were measured and analyzed in a wide temperature range: from room to human body and further to a hyperthermic temperature resulting in tissue morphology change. The results show that the luminescence signal of UCNPs and ZnCdSNPs placed within the tissue is reasonably good sensitive to temperature change and accompanied by phase transitions of lipid structures of adipose tissue. The most likely that the multiple phase transitions are associated with the different components of fat cells, such as phospholipids of cell membrane and lipids of fat droplets. In the course of fat cell heating, lipids of fat droplet first transit from a crystalline form to a liquid crystal form and then to a liquid form, which is characterized by much less scattering. The results of phase transitions of lipids were observed as the changes in the slope of the temperature dependence of the intensity of luminescence of the film with nanoparticles embedded into tissue. The obtained results confirm a high sensitivity of the luminescent UCNPs and ZnCdSNPs to the temperature variations within thin tissue samples and show a strong potential for the controllable tissue thermolysis.