Vol 63, No 9 (2018)

The molecular-conformal, morphological, and kinetic characteristics of selenium-containing nanosystems (NSs) based of biocompatible polymer matrices of different origins modified Se⁰ nanoparticles for the Se⁰ : polymer mass ratio ν = 0.1 have been analyzed using static and dynamic light scattering methods, UV spectroscopy, flow birefringence, and atomic force and transmission electron microscopies. We have determined the rate constants for the formation of selenium-containing NSs, the size characteristics of the corresponding nanostructures, as well as their shape, molecular mass, and density. It is found that isolated dense spherical polymolecular selenium-containing nanostructures are formed in the aqueous solution. Our results can be used as the physicochemical foundation for the modification of polymer materials with clearly manifested physiological activity by biogenic elements in the zero-valent form.

A mean-field model of intermittent transport of particles, molecules or organelles is proposed. A particle may be in one of two phases: the first is a ballistic (active) phase, when the particle runs with constant velocity in some direction, and the second is a Brownian (passive) phase, when the particle diffuses freely. The particle can instantly change the phase of motion. The distribution of the duration of the passive phase (the free path distribution) is exponential, while that of the active phase is arbitrary. In the case that transitions between the phases are very frequent an approximation to the model is derived. An example is given which shows that the use of the exponential distribution of free paths, when it is actually non-exponential, may lead to significant errors in solutions.

The main ideas of an electron-conformational (EC) model of ligand-activated ryanodine channels (RyR) that reduces many degrees of freedom of this gigantic nanoscopic molecular complex to two so-called electron and conformational degrees of freedom are presented. In the toy model, the conformational potential or energy profile of the RyR channel represents two branches that describe the dependence of energy on the conformational coordinate (reaction coordinate) in the initial and ligand-activated states, respectively. A model extension that takes into account both the tetrameric structure of the RyR channel and additional (orthogonal) rotational conformational mode has been considered. The EC model has been demonstrated to give a biophysical basis to the traditional phenomenological model of Markov chains. To demonstrate the possibilities of the EC model, we refer to examples of model description of the dynamics of isolated RyR channels and clusters of RyR channels in release units of the heart cell.

We have analyzed the decay of fluorescence intensity in indole dissolved in propylene glycol under two-photon excitation by linearly and circularly polarized femtosecond laser pulses in the wavelength range 475–510 nm. The dependences of fluorescence intensity I₀, anisotropy r, and parameter Ω on the excitation energy have been determined and analyzed. In particular, a nonmonotonic behavior of I₀ indicating the increase of indole excited state density in the excitation energy range above 5.1 eV and the anisotropy sign reversal due to the variation of the symmetry of indole vibronic states have been observed and interpreted theoretically.

The effect of the electric field of a medical electret on the basis of tantalum pentoxide (Ta₂O₅) on the viability of human fibroblasts, multipotent mesenchymal stromal bone marrow cells, osteocytes, and chondrocytes cultivated on the surface of tantalum orthopedic implants with an electret coating was studied in vitro. Using the methods of photocolorimetic analysis and scanning electron microscopy, difference in the metabolic activity and cell morphology, in the character of the cell attachment to the implants and distribution by their surface, associated with the value and character of the electric charge distribution on the surface of these implants and the type of cellular test systems, were detected. Unclear mechanisms of the effect of the electric field of medical electrets on the functional activity of different types of the organism cell and tissues dictate the need for further experimental developments and fundamental studies in this field.

Сomposite particles based on monodisperse spherical mesoporous silica particles (MSMSPs) are synthesized by noncovalent binding of organic active components (propidium iodide fluorescent dye and Radakchlorin photosensitizer) from aqueous solutions. Hybrid particles with a core–shell structure are synthesized, which are MSMSPs filled with Fe₃O₄ and coated with mesoporous silica, the internal surface of which is modified by Fluorescein isothiocyanate (FITC) fluorescence dye by means of chemisorption. The toxicity and penetration of the obtained particles into the cells of the HeLa and K-562 cell lines were studied. The effective photodynamic action of MSMSPs containing Radachlorin in mesopores is demonstrated, which indicates the promise of using the synthesized composite particles for medical purposes.

Monodisperse polymeric particles have great potential in biomedical and physical applications. Modern high-throughput droplet microfluidic technologies make it possible to produce monodisperse water-in-oil macroemulsions with desired properties. Polymerization in a macroemulsion transforms it to a suspension of microparticles. These particles may be viewed as containers for targeted delivery of drugs and also as bioink for 3D printing of tissues and organs. Conditions for formation of PEGDA and polyacrylamide particles using a microfluidic flow-focusing emulsion generator have been studied. Manufactured microparticles have been characterized by their geometrical sizes and mechanical properties. In addition, the diffusion escape of small molecules from microparticles has been studied using Rhodamine B fluorescent dye.

In this work, the conditions of spectrophotometric evaluation of the ninhydrin assay for L-lysine in a water dimethyl sulfoxide solution were investigated. The absorption spectrum of the L-lysine–ninhydrin reaction product exhibited two maxima at 420 and 500 nm. It was shown that pH of the reaction medium affected the intensity of the product color. The stability of the ninhydrin reaction products was the highest at pH 8–9. The phase proportion of the water–organic solution had little effect on the optical density of the product. The absorption spectra of the ninhydrin reaction products of L-lysine derivatives: N^α-boc-lysine and N^ε-z-lysine, indicated that it was the α amino group of lysine that participated in the reaction.

The samples of porous silicon (por-Si) particles in three size ranges (60–80, 250–300, and 500–600 nm) are obtained by electrochemical anodic etching of single-crystal silicon in an electrolyte based on an HF solution, followed by a change in the modes of ultrasonic treatment and homogenization. A complex characterization of particles was carried out by scanning electron microscopy, photon cross-correlation spectroscopy, and X-ray photoelectron spectroscopy. In vitro biocompatibility models using unicellular organisms of infusoria Paramecium caudatum Keln are applied to demonstrate the low toxicity of the samples at concentrations used for intravenous administration. The systemic in vivo biodistribution was studied for the por-Si 60–80 nm sample using adult Wistar rats. Introduced nanoobjects are found in the liver and heart tissues without significant changes in shape or size and predominantly in the oxidized state. Possibilities of using por-Si samples as matrices for transporting pharmaceuticals with intravenous administration are studied by assessing the intensity of the ototropic effect of gentamicin. An objective audiologic method for studying the amplitude of otoacoustic emission revealed the largest otodepressive effect of gentamicin when submicrometer-sized por-Si particles (500–600 nm) was used as a disperse system for drug delivery. Thus, modifications of the conditions for the synthesis of por-Si nanoparticles are promising directions in obtaining physicochemical parameters of transport particles that are optimal for specific tasks of targeted drug delivery.

Fragment analysis of DNA by the capillary gel-electrophoresis method is an effective tool for studying the DNA structure, which has a large number of applications (in particular, for genetic expertise of breeds and breed samples of a number of important crops). Fragment analysis of DNA is carried out in several stages. The stage of processing of the results of investigations includes the procedure of detection of peaks for standard DNA fragments. We list the features of the spectrum of the DNA fragment distribution, which necessitate the development of a new method for detecting peaks of a standard. We propose a method for their search based on comparison of the aggregate of standard lengths of DNA fragments and spectral peaks and describe the algorithm for implementing this method. We also consider in detail the critical stage of the algorithm, i.e., the choice of the threshold for the procedure of detection of peaks in the spectrum. The advantages and disadvantages of the method are enumerated and the results of testing are considered.

Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are modern methods for visualization in diagnostic nuclear medicine. SPECT is known as a workhorse in cardiology, and PET is the gold standard in oncology. The development of nuclear medicine is provided by cooperation of physicists, mathematicians, biologists, medical doctors, and radio-chemists. In spite of extensive clinical applications, several problems may lead to false diagnoses. In particular, the correction of attenuation of gamma radiation in human organs must be taken into account. For interpretation and evaluation of such an effect on the clinical results, we perform physico-mathematical simulation of the SPECT diagnostics in cardiology in the absence and presence of the correction of attenuation. A brief review of the state-of-the art is presented. The simulation employs the first Russian anthropomorphic mathematical phantom that describes the distribution of radio-pharmacological agent (^99m Tc-methoxyisobutylisonitrile) in chest organs of a typical male patient. A model for calculation of raw images is developed with allowance for attenuation of radiation in biological tissues and the effect of collimator and detector. The results of the proposed models and calculated images are compared with clinical images obtained at the Meshalkin Institute of Circulation Pathology (Novosibirsk) and Myasnikov Institute of Clinical Cardiology (Moscow). Statistical algorithms are developed for the solution of the inverse problem of image reconstruction based on the entropy principle. The clinical and physico-mathematical approaches are compared in the evaluation of the effect of correction on the quality of reconstructed images of the left ventricle of myocardium.

Efficiencies of optical pairs consisting of fast low-noise uncooled immersion LEDs and photodiodes based on InAsSb solid solution are studied. The proposed optical pairs are promising for applications in compact low-voltage sensors of carbon dioxide. The threshold sensitivity of such a sensor is several hundreds of ppm, and the measurement error is no worse than 5% in a wide range of concentrations (up to 10 v/v%) at a relatively high time resolution (50 ms) and a sample volume of no greater than 50 mL. Relatively high working rate and low volume of the sample improve diagnostics in capnography and allow applications in pediatrics and side-stream capnography including measurements of instantaneous CO₂ concentration in the course of breathing.