The molecular weight distribution of modified amino-formaldehyde resins synthesized at various melamine- and carbamide-to-formaldehyde molar ratios and catalyst modifier and diethylene glycol amounts was studied. Chromatograms of the obtained amino-formaldehyde resins are presented.

Branched polystyrenes are synthesized by the radical copolymerization of styrene and divinylbenzene with reversible inhibition (in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl) under deteriorating thermodynamic quality of the solvent. The resulting polymers are studied by size-exclusion chromatography combined with static light scattering, ozonolysis, NMR spectroscopy, and differential scanning calorimetry. The branched polymers synthesized by living radical polymerization are characterized by lower intrinsic viscosity values than their linear analogs. Kuhn–Mark–Houwink parameters for these polymers in a tetrahydrofuran solution ( а = 0.29) confirm the nonlinear architecture of macromolecules and a high content of pendant double bonds comparable in the order of magnitude with their theoretical content in the absence of the cyclization reaction indicate their branched structure. The glass transition temperature of the branched polystyrenes is 20–35°С lower than the glass transition temperature of the linear polystyrene.

Currently, there is a significant increase in the incidence of cancer of the central nervous system. Determination of the boundaries of intracerebral and intramedullary tumors is especially difficult. The urgency of the problem of determining the boundaries of astrocytic tumors is due to the peculiarities of their growth along myelinated nerve fibers and vessels, leading to the infiltration of healthy white matter by tumor cells, which affects the high frequency of postoperative relapses. The complexity of surgery for intramedullary tumors of the spinal cord is that the tumor does not always have a clear border and the risk of injury is high due to the smaller size of the operated area compared to the brain. Reliable information regarding the volume of the resected tumor should be obtained by intraoperative imaging. The solution to this problem is implemented mainly in three directions: the use of intraoperative computed tomography, magnetic resonance imaging and ultrasound scanning, and various combinations of these methods. Unfortunately, all these methods of intraoperative diagnostics do not allow real-time examination of tissues in an operating wound and/or do not provide a simultaneous analysis of both structural and metabolic changes. The limitations of intraoperative navigation methods in neurosurgery have led to the relevance of the development of an accurate spectroscopic method for in vivo determination of the content of specific metabolic markers and structural changes accompanying the development of the tumor process in the nervous tissue. Various approaches to intraoperative navigation based on optical spectroscopy are called optical biopsy. In this article, we present the methods and tools developed in recent years for spectroscopic guidance in neurooncology. First of all, this, of course, concerns the analysis of spectral dependences recorded before, during and after tumor removal. We have used such modalities of optical spectroscopy as fluorescence, diffuse reflectance spectroscopy and spontaneous Raman scattering. An equally important issue on the way to increasing the efficiency of tumor resection is the development of new instrumentation; therefore, we have developed a number of new devices, which are a combination of well-known neurosurgical instruments and laser and fiber-optic technologies. Last but not least is the issue of rapid classification of the studied tissues based on the recorded signals, which was solved by us using machine learning methods.

Radical polymerization of unsaturated alkoxy-NNO-azoxy compounds was explored. Polymethoxy-NNO-azoxyethene, the first energetic polymer based on alkoxy-NNO-azoxy compounds, was obtained, and its major characteristics were studied. Thermodynamic calculations show that poly(methoxy-NNO-azoxyethene) may be of interest as a polymer component of active binders for solid composite rocket propellants.

The studies show the dynamics of photosensitizers accumulation in various grain areas during germination and their photodynamic activity against pathogenic microflora (Fusarium, Bipolaris, Alternaria). Four photosensitizers (methylene blue, Chlorin E6, aluminum phthalocyanine in molecular- and nanoform) were used in the work. The accumulation level of methylene blue and aluminum phthalocyanine in molecular form in infected by Alternaria and Fusarium fungi grains was 4-5 times higher than in control on the 4th day. The possibility of pathogenic microflora inactivation using aluminum phthalocyanine was shown.

The use of shortwave-infrared radiation (1-2 μm spectral range) opened an opportunity for deep biotissue imaging due to low absorption and scattering in this range. The shortwave-infrared emitters based on Yb-Er-Tm and Yb-Er-Ho tridoped core-shell NaGdF4 nanoparticles were studied in this work. The ability to tune the luminescence intensity in 1000-1600 nm range by changing the rare-earth ions concentration ratio was shown. The energy transfer processes between rare-earth ions and their influence on each luminescence band and integral intensities were studied. Optimal rare-earth ions concentrations to obtain shortwave-infrared emitters with several intense luminescence bands were chosen. It was shown that coating of nanoparticles with passive shell effectively prevents the quenching of their luminescence in biological media.

Inorganic nanoparticles containing rare-earth ions are of particular interest as luminescent contrasting agents for obtaining optical images from the depth of biological tissues. Stable aqueous colloidal solutions of Nd3+: LaF3 nanoparticles with strong luminescence in the NIR and visible spectral ranges under NIR laser excitation were synthesized by hydrothermal microwave treatment. The results of their luminescence visualization under system-wide administration to laboratory animals with transplanted tumors are presented. The histological distribution of the nanoparticles is verified by laser upconversion microscopy.

Abstract The kinetic and molecular weight characteristics of the copolymers of n-butyl acrylate and styrene (95: 5 wt.%) obtained by the method of radical polymerization with reversible chain transfer were studied. The dependence of the refractive index on the molecular weight of the copolymers of n-butyl acrylate and styrene is shown.

In neurosurgery exists a need to treat deep-seated brain tumors by stereotactic photodynamic therapy. Since access to tumor is limited and carried out through a small diameter hole, the choice a suitable equipment is difficult. To improve the treatment method, we have developed a single-fiber system for delivery laser radiation and determining the photosensitizer concentration in a biological object.

A description of the development stages of a polymer composition designed to ensure the restoration of the operational characteristics of large-diameter pipelines (d = 1100–1400 mm) using metal split sleeves, as well as for filling and sealing mixtures in the repair and construction industry, is presented. It is shown that the developed epoxy–urethane composition of a low-temperature curing adhesive paste provides a stable and safe pipeline restoration without interrupting the product transportation cycle.

The thermal and thermomechanical properties of polyurethanes based on isophorone diisocyanate and polyfurit crosslinked using various curing agents are studied by differential scanning calorimetry and dynamic mechanical analysis. Two transitions are observed on thermograms in the temperature range from –100 to +150°С. The first transition detected at a temperature below –60°С corresponds to the glass transition temperature of soft ester segments. A broad endothermic region (near 100°С) is related to the melting of crystal-like ordered structures formed by strong hydrogen bonding between hard segments. The relationship between the spectral-kinetic behavior of the photochromic compound introduced into the polymer matrix and the properties of the polyurethanes is investigated. The rate of photochemical transformations of the photochromic compound covalently bonded to the matrix may depend on the stage of the polymerization process at which it is introduced into the polymer.

To improve methods of laser hyperthermia for the treatment of bulk malignant neoplasms, an urgent task is the development of techniques and devices that automatically control heating at a given tissue depth and ensure its uniformity. The article proposes the concept of a system for performing hyperthermia with real-time spectroscopic temperature control and surface cooling, which allows to record spectra of diffusely scattered radiation and fluorescent signal from various depths of biological tissues by the means of the variation of the angle and distance between the fiber source of laser radiation and the receiving fiber. Theoretical and experimental modeling of the spatial distribution of diffusely scattered radiation and temperature inside the tissue with a fiber optic device providing surface cooling of the irradiated tissue, and recording spectral information from a given depth in real time, is presented. Simulation of radiation propagation in biological tissues, depending on the distance between the source and the receiver and the angle of their tilt, was carried out using the Monte Carlo method. Modeling of the temperature distribution inside the tissues was carried out by means of a numerical solution of the heat conduction equation. Experimental modeling was carried out on phantoms of biological tissues simulating their scattering properties as well as accumulation of the investigated nanoparticles doped with Nd3+ ions. It was shown that inorganic nanoparticles doped with rare-earth Nd3+ ions can be used as temperature labels for feedback to the therapeutic laser. According to the results of the theoretical simulation, optimal configurations of the relative arrangement of the fibers were chosen, as well as the optimum surface cooling temperatures for the given power densities. The heating of the phantom of the neoplasm containing the investigated nanoparticles doped with Nd3+ ions by laser radiation with an 805-nm wavelength and power density of 1 W/cm2 up to 42 °C at a depth of 1 cm while maintaining the surface temperature within the limits of the norm was demonstrated.

Recent developments in the field of biophotonics facilitate the raise of interest to inorganic nanoparticles (NPs) doped with Nd 3+ ions, because of their near-infrared (NIR) absorption. These NPs are interesting bioimaging probes for deep tissue visualization, while they can also act as local thermometers in biological tissues. Despite the good possibilities for visualization of NPs with Nd 3+ ions in NIR spectral range, difficulties arise when studying the cellular uptake of these NPs using commercially available fluorescence microscopy systems, since the selection of suitable luminescence detectors is limited. However, Nd 3+ ions are able to convert NIR radiation into visible light, showing upconversion properties. In this paper we found optimal parameters to excite upconversion luminescence of Nd 3+ :LaF 3 NPs in living cells and to compare the distribution of the NPs inside the cell culture of human macrophages THP-1 obtained by two methods. Firstly, by detecting the upconversion luminescence of the NPs in VIS under NIR multiphoton excitation using laser scanning confocal microscopy and secondly, using transmission electron microscopy.

Recent developments in the field of biophotonics facilitate the raise of interest to inorganic nanoparticles (NPs) doped with Nd3+ ions, because of their near-infrared (NIR) absorption. These NPs are interesting bioimaging probes for deep tissue visualization, while they can also act as local thermometers in biological tissues. Despite the good possibilities for visualization of NPs with Nd3+ ions in NIR spectral range, difficulties arise when studying the cellular uptake of these NPs using commercially available fluorescence microscopy systems, since the selection of suitable luminescence detectors is limited. However, Nd3+ ions are able to convert NIR radiation into visible light, showing upconversion properties. In this paper we found optimal parameters to excite upconversion luminescence of Nd3++:LaF NPs in living cells and to compare the distribution of the NPs inside the cell culture of human macrophages THP-1 obtained by two methods. Firstly, by detecting the upconversion luminescence of the NPs inVIS under NIR multiphoton excitation using laser scanning confocal microscopy and secondly, using transmission electron microscopy.

Upconversion nanoparticles have many advantages for application in bioimaging, such as ability to use infrared excitation, no autofluorescence, no photobleaching, large anti-Stokes shift and sharp emission bands. In addition, heating of upconversion nanoparticles under laser irradiation and thermo sensitive luminescence bands enable to perform photothermal therapy with temperature control in the thickness of biological tissues. However, the 980 nm wavelength which is widely used to excite upconversion luminescence is well absorbed by water. In this regard, it was proposed to optimize the excitation wavelength in order to ensure the selectivity of heating on the one hand and an intense luminescent signal for effective spectroscopic thermometry on the other hand.

The results of the authors’ studies on development of a multilayer photochromic sun-protective energy-saving polymer film able of reversibly changing its light transmission depending on the intensity of the activating irradiation and of permanently reflecting thermal radiation were analyzed.

The study of bioimaging with controlled depth using upconversion nanoparticles under near-infrared excitation was performed in this work. Monte Carlo simulation was performed to determine optimal distance between the fiber - source of laser radiation, and the receiving fiber for obtaining the signal from maximal depth in biological tissue. Also theoretical modeling of the spatial distribution of diffusely scattered radiation inside the tissue depending on wavelength is presented. Penetration depth for wavelengths corresponding to the upconversion luminescence was calculated. Experimental modeling was carried out on phantoms of biological tissues simulating their scattering properties as well as accumulation of the investigated nanoparticles doped with rare earth ions. Measurements were performed using NaGdF4 nanoparticles doped with Yb3+, Er3+ and Tm3+ rare earth ions, which demonstrated several luminescence bands from the blue (475nm) to the near-infrared (800 nm) regions of the spectrum under 980 nm excitation. The different penetration depth of various wavelengths in biotissue allows us to estimate the depth from which the signal was obtained using luminescence intensity ratio (LIR). Due to non-linearity of upconversion process, pumping power dependences of luminescence intensity was taken into account. The number of involved photons for each spectral band was estimated and intensity ratio of emission bands was calculated. Based on calculations and experimental measurements, the theoretical and experimental luminescence intensity ratio for different depths was estimated. The experimental study was performed on biological tissue phantoms containing Lipofundin (R) with red blood cells and has shown good agreement with calculations. The use of theoretically calculated LIR allows us to solve the inverse problem and estimate the depth from which the signal was obtained.

Laser hyperthermia is one of the promising methods for treatment of oncological diseases. For routine clinical use of hyperthermia, it is necessary to control the uniformity and localization of heat within the tumor. Local heating can be achieved by using special thermal agents, such as nanoparticles doped with rare-earth ions. Measurement of the temperature of the thermal agents will allow timely regulation of the applied laser radiation excitation power and optimization of the hyperthermia process.The paper presents the results of a study on the non-invasive determination of the YPO4nanoparticles doped with Nd3+ temperature with sensitivity of 0.2% °С-1in 30-60°С temperature range. The temperature of the nanoparticles was calculated from the Nd3+ luminescence spectra in the 800-1000 nm range under excitation into4F5/2energy state by 805 nm laser. A calibration procedure for recalculating the ratio of the luminescence intensities from the Stark sublevels of the4F3/2Nd3+ state into the values of the real NP temperature in accordance with the Boltzmann distribution is given. An algorithm for calculating luminescence intensities for individual Stark components is proposed. After calculating the intensities corresponding to each individual Stark component, all the intensities related to the transition from the upper and lower Stark sublevels of the4F3/2state are summed, and then their ratio is calculated. The resulting ratio is normalized to the value of the ratio at room temperature and, in accordance with the calibration dependence, is recalculated into the NP heating temperature. It was demonstrated that the investigated 1%Nd3+:YPO4nanoparticles can be used as "primary” thermometers that do not require additional recalibration to evaluate the temperature in the range used for hyperthermia.