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Currently, tissue engineering technologies are promising for the restoration of damaged organs and tissues. For regeneration of electrically conductive tissues or neural interfaces, it is necessary to provide electrical conductivity for the transmission of electrophysiological signals. The developed biocomposite structures presented in this article possess such properties. Their composition includes bovine serum albumin (BSA), gelatin, eosin-Y and single-walled carbon nanotubes (SWCNTs). For the first time, a biocomposite structure was formed from the proposed hydrogel using a nanosecond laser, and a two-photon absorption cross section value of 580 GM was achieved. Increased viscosity over 3 mPa∙s and self-focusing with a nonlinear refractive index of 42 × 10−12 cm2/W make it possible to create a biocomposite structure over the entire specified area. The obtained electrical conductivity value was 19 mS∙cm−1, due to the formation of effective electrically conductive networks. For a biocomposite with a concentration of gelatin 3 wt. %, formed by low-energy near-IR pulses, the survival of Neuro 2A nerve tissue cells was confirmed. The obtained results are important for the creation of new tissue engineering structures and neural interfaces from a biopolymer hydrogel based on the organic dye eosin-Y and carbon nanotubes by two-photon polymerization. [ABSTRACT FROM AUTHOR]

Purpose. The aim of the work is to study nanocomposites created by laser evaporation of waterprotein dispersion of carbon nanotubes. The studies are aimed to determine the features of the interaction between the composite components, as well as to the analysis of the internal and surface structures of nanocomposites, depending on the type and concentration of the used nanotubes. Methods and methodology. For the manufacture of nanocomposites single-walled carbon nanotubes of two types were used. Nanotubes of the fi rst type (SWCNTs I) were synthesized by the electric arc method on a Ni/Y catalyst. The average diameter of nanotubes was 1.4–1.8 nm, length ~ 0.3–0.8 microns. Nanotubes of the second type (SWCNTII) were obtained by the method of gas-phase synthesis. The average diameter was ~ 2–3.5 nm, their length was more than 5 microns. To create nanocomposites, a laser method was used to evaporate the waterprotein dispersion of nanotubes. However, the water dispertion of bovine albumin (25 %) and collagen (2 %) was used as a protein matrix. The binding of protein molecules to carbon component was described by Raman spectroscopy. To carry out a comprehensive analysis of the structure and microporosity of nanocomposites, the X-ray microtomography method was used. The study of the specifi c surface and pore volume of the samples was carried out with the use of the method of low-temperature nitrogen porosimetry. Results. There was a local boiling up of the dispersion of single-walled carbon nanotubes, which was accompanied by the appearance of inhomogeneities in the form of an evolved gas and subsequently produced the production of solid nanocomposites by laser evaporation of the aqueous dispersion of carbon nanotubes with the protein matrix. At the same time, the protein component in nanocomposites undergoes irreversible denaturation. It can be as a biocompatible binding material, which is a source of amino acids for biological tissues during the implantation of nanocomposites in the body. While manufacturing of nanocomposites, carbon nanotubes actively absorb radiation, creating an additional thermal heating of the organic components of tissue-engineering structures. As the temperature rises, the number of damages of the weak bonds in the tertiary structure of the protein, what allows the molecule to modify its position in space, increases. It is assumed that the heating from laser radiation and the additional heating from nanotubes accelerate these processes and contribute to the adhesion of the organic part of the composite to the carbon matrix. The internal structure of the SWCNTI nanocomposites was the most homogeneous. With an increase in concentration from 0.01 to 0.1 %, the average size of micropores increased from 45 to 85 μm and the sample porosity in general from 46 to 58 %. The share of open pores for two types of SWCNTI concentrations was 2 % of the total volume of the composite. SWCNTII-based nanocomposites with both concentrations had a wide range of micropore sizes from 33 to 314 μm. These samples with a concentration of 0.1 % nanotubes had a porosity of up to 73 % with an open pore fraction of 8 %. The presence of mesopores with an average size of up to 46 and 49 nm was found in SWCNTI-based composites, respectively, for concentrations of nanotubes of 0.01 and 0.1 %. An increase in the concentration of nanotubes led to a decrease in the specifi c values of the surface and pore volume of the sample. Conclusions. In this work, nanocomposites were created by laser evaporation of the water-protein dispersion of carbon nanotubes. The features of the interaction between the components of the composite were identifi ed. The analysis of the internal and surface structures of nanocomposites was carried out depending on the type and concentration of the used nanotubes. The structural characteristics of nanoscale composites should positively infl uence on the adhesive characteristics of the lateral processes of cells in various biotissues. The porosity of nanocomposites for biomedical applications is important for triggering the processes of neovascularization and neoinnervation in the repair of defects of biotissues. Thus, the nanocomposites studied in this work can be used as tissue-engineering matrixes to repair bulk defects of biological tissues.

The development of suitable protection against laser radiation has proven challenging due to the lack of predictive models. The purpose of this article is to exclude the existing drawback by creating a universal strategy based on correlations between experimental and theoretical data characterizing the nonlinear optical properties of absorbers, for which a series of low-symmetry penta(chloro)cyclotriphosphazenesubstituted monophthalocyanines was chosen. To search for correlations on a small series of dyes, we used the advanced algorithm CORRELATO, which has been proven to construct even the most unusual relationships demonstrated in our previous works. Due to the reducing symmetry of molecules, large values of the nonlinear absorption coefficient (more than 3000 cm GW-1) and, as a result, wide dynamic ranges (up to 630) with a high degree of attenuation of nanosecond laser radiation (10-20 times) were achieved. The use of the finite-field DFT method has allowed the calculation of dipole moments, polarizabilities and hyperpolarizabilities. The numerical data obtained during the calculations were used in correlations of theory vs. experiment to derive mathematical expressions (inequalities) to assess the effectiveness of absorbers in limiting the power of laser radiation. [ABSTRACT FROM AUTHOR]

The article presents the results of the creation of composite materials. Laser irradiation in the near infrared region (970 nm) of water-albumin dispersion of single-layer carbon nanotubes (SLCNT) is characterised by an intensive absorption of radiation, which is accompanied by nanotube heating. Signifi cant warming occurs at the ends of nanotubes and in the areas of localised defects where the thermal conductivity is signifi cantly reduced. In terms of chemical reaction, the open ends of nanotubes and areas with defects appear to be most active, thus, the idea of splicing SLCNT in the defective areas was taken as the basis. Numerical simulation showed that the process of nanotube matching in the frame starts when the laser heats to a temperature of 80–100 oC. This process occurs within a few nanoseconds. The graphs of enthalpy allow us to conclude that the process of SLCNT frame forming with four defects in the form 1V (single carbon atom vacancies) present it the region of the tube junctions results in the greatest energetic advantage. In composite materials, the bonding of SLCNT with albumin molecules occurs though the Glu and Asp amino acid residues. The interaction energy between the nanotube frame and the albumin matrixis up to 580 kJ/mol. Molecular dynamic simulations show that an increase in the number of oxygen atoms leads to a decrease in the interaction energy between SLCNT and albumin. The attachment of the oxygen atoms to the SLCNT leads to the distortion of nanotubes, which increases with the increase in the number of oxygen atoms. The change of the attachment points of the oxygen atom to the nanotube oxygen atoms allows confi guring the desired shape of the nanotube frame in the albumin matrix. Composite materials based on SLCNT water-albumin dispersion have a developed surface with periodic peaks and troughs. This can be seen from the atomic force microscopy images and is associated with the carbon nanotube framework which is formed under laser radiation. The pore size ranges between 30-120 nm. Composite materials can provide superior adhesion of cells planted on their surface. It can be used as a tissue-engineered matrix to restore three-dimensional structure of bone and connective tissue.

Objectives: This study describes the effects of interval hypoxic training and electrical muscle stimulation (EMS) technology on human productivity with the following metrics: biochemical indices, cognitive abilities, changes in oxygenated (HbO) and deoxygenated (Hb) hemoglobin concentrations over the prefrontal cortex, and functional connectivity via electroencephalography (EEG). Methods: All measurements according to the described technology were made before the start of training and one month later, right after it ended. The study involved middle-aged Indo-European men. Specifically, there were 14, 15, and 18 participants in the control, hypoxic, and EMS groups, respectively. Results: EMS training improved reactions and nonverbal memory but decreased attention scores. Functional connectivity decreased in the EMS group while it increased in the hypoxic group. A result of the interval normobaric hypoxic training (IHT) was significantly improved contextual memory, with a p-value = 0.08. Conclusions: It was found that EMS training is more likely to cause stress on the body than positively affect cognitive functions. At the same time, interval hypoxic training can be considered a promising direction for increasing human productivity. The data obtained during the study can also help in the timely diagnosis of insufficient or overestimated indicators of biochemistry. [ABSTRACT FROM AUTHOR]