Sergey Makaev

Three groups of touch-spun 3D scaffolds with uniform fiber diameters and varying interfiber spacing were studied to identify optimal conditions for NIH/3T3-GFP fibroblast growth. All scaffold groups exhibited higher cell viability relative to control levels after 14 days of culture, with the highest viability observed for scaffolds with a 50.61 ± 15.35 μm interfiber spacing. Although cell counts indicated comparable cell growth across groups, scaffolds with medium and large interfiber spacing demonstrated an improved capacity to sustain viable cells without necrotic core formation. These findings provide insight into the optimal structural design of touch-spun 3D scaffolds for tissue engineering applications.

3D touch-spun scaffolds support dense fibroblast cell cultures for 21 days, enabling healthy growth of up to 6.5 million cells.

Label-free cell sorting methods and materials are developed in this work. The microstructured thermoresponsive surfaces made of poly(glycidyl methacrylate) (PGMA) and poly(N-isopropylacrylamide-co-glycidyl methacrylate) (PNIPAM-co-GMA) are prepared by phase separation on the submicron scale in thin films and then cross-linked and covalently grafted to the substrate. PGMA domains are used for cell adhesion, while the PNIPAM-co-GMA matrix pushes cells off the surface at a temperature below the lower critical solution temperature (LCST). The microstructure formation and swelling-shrinking caused by changes in temperature are studied experimentally and by using dissipative particle dynamics computer simulations. Experiments with RAW 264.7 murine macrophage-like cells, NIH3T3/GFP murine fibroblasts, and HaCaT human skin keratinocytes (unlabeled and GFP-positive strains) demonstrate successful cell sorting based on weak and nonspecific interactions with reconfigurable thermoresponsive microstructured surfaces. Efficient sorting with a separation factor of >50 is achieved if the push-off force is adjusted to a level between the adhesive forces of the separating cells. This experimental finding is supported by Monte Carlo simulations of cell adsorption and detachment on the microstructured surfaces. The experiments and simulations show that efficient cell sorting is possible for weak to moderate cell adhesion to the surfaces. However, the method is not successful for very weak or very strong adhesion. We demonstrate that cell adhesion to the microstructured surfaces can be adjusted by changes in the conditions of the phase separation at the stage of film formation and by varying the incubation time of the cells on the microstructured surfaces.

The movement of small particles and molecules through nanopore membranes is widespread and has far-reaching implications. Consequently, the development of mathematical models is essential for understanding these processes on a micro level, leading to deeper insights. In this endeavor, we suggested a model based on a set of empirical equations to predict the transport of substances through a solid-state nanopore and the associated signals generated during their translocation. This model establishes analytical relationships between the ionic current and electrical double-layer potential observed during analyte translocation and their size, charge, and mobility in an electrolyte solution. This framework allows for rapid interpretation and prediction of the nanopore system's behavior and provides a means for quantitatively determining the physical properties of molecular analytes. To illustrate the analytical capability of this model, ceria nanoparticles were investigated while undergoing oxidation or reduction within an original nanopore device. The results obtained were found to be in good agreement with predictions from physicochemical methods. This developed approach and model possess transferable utility to various porous materials, thereby expediting research efforts in membrane characterization and the advancement of nano- and ultrafiltration or electrodialysis technologies.

The polymer brush architecture of the end-tethered polymer molecules is one of the most widely used efficient methods to regulate interfacial interactions in colloidal systems found in live matter and manufactured materials. Emerging applications of polymer brush structures require solutions to new tasks in the control of interfacial interactions. The rapid development of live cell manufacturing relies on scalable and efficient cell harvesting methods. Stimuli-responsive surfaces made of surface-grafted poly(N-isopropylacrylamide) (PNIPAM) can bind and detach the adherent cell upon changes in temperature and have been used for cell growth and harvesting. The applications are limited by the requirement to satisfy a range of PNIPAM coating characteristics that depend on the dimensions of the integrin complex in the cell membrane and the basal surface. The analysis of the microstructured surfaces, when adhesive and disjoining functions of the microdomains are decoupled, shows that many limitations of PNIPAM one-component coatings can be avoided by using a much broader range of structural characteristics of the microstructured interfaces composed of alternating disjoining PNIPAM domains and adhesive polymeric domains with cell-affinity functional groups. Temperature-controlled reversible adhesion to such microstructured interfaces is studied here experimentally with model systems of solid spherical particles and by employing simulations for solid and soft membranes interacting with the microstructured surfaces to mimic interactions with soft and solid disk-like particles.

For the first time, membranes based on poly(1-trimethylsilyl-1-propyne) (PTMSP) with 5–50 wt% loading of hyper-crosslinked polystyrene sorbent particles (HCPS) were obtained; the membranes were investigated for the problem of effective removal of volatile organic compounds from aqueous solutions using vacuum pervaporation. The industrial HCPS sorbent Purolite Macronet™ MN200 was chosen due to its high sorption capacity for organic solvents. It has been found that the membranes are asymmetric when HCPS content is higher than 30 wt%; scanning electron microscopy of the cross-sections the membranes demonstrate that they have a clearly defined thin layer, consisting mainly of PTMSP, and a thick porous layer, consisting mainly of HCPS. The transport and separation characteristics of PTMSP membranes with different HCPS loading were studied during the pervaporation separation of binary and multicomponent mixtures of water with benzene, toluene and xylene. It was shown that the addition of HCPS up to 30 wt% not only increases the permeate fluxes by 4–7 times, but at the same time leads to 1.5–2 fold increase in the separation factor. It was possible to obtain separation factors exceeding 1000 for all studied mixtures at high permeate fluxes (0.5–1 kg/m²∙h) in pervaporation separation of binary solutions.

В процессе вскрытия фосфатных пород и извлечения основного компонента методом кислотной экстракции необходима стадия выделения нерастворимого остатка из полученных суспензий с помощью фильтрации. Это обеспечит повышение концентрации питательных элементов в продуктах переработки природных фосфоритов, используемых в качестве модельных минералов. Нерастворимый остаток на фильтровальной перегородке является фильтрующим слоем, плотная структура которого препятствует эффективному процессу разделения системы жидкость-твердое. С целью интенсификации процесса фильтрации азотнокислотной суспензии на основе низкокачественного высококремнистого фосфорита Полпинского месторождения исследовано влияние сульфатных добавок: серной кислоты, сульфата аммония и сульфата калия на структуру осадка и, соответственно, время фильтрации суспензии и промывки осадка. Содержание вводимых добавок варьировали в интервале 10 - 30 масс. %. Результаты исследования микроструктуры осадков – вертикального сечения и их поверхности, полученных с помощью метода сканирующей электронной микроскопии, позволили установить, что введение исследуемых добавок приводит к увеличению порозности слоя за счет образования крупных друз из монокристаллов дигидрата сульфата кальция – гипса. Это улучшает фильтрационные свойства слоя осадка, сокращая время фильтрования и промывки. Следует отметить, что при прочих равных условиях, эффективность добавки сульфата калия выше в сравнении с добавками серной кислоты и сульфата аммония. Ее преимущество заключается не только в улучшении реологических свойств суспензий, но и наличии калия в системе в качестве питательного компонента при переработке азотнокислотной вытяжки на комплексные удобрения. Экспериментально установлена эффективная концентрация сульфата калия в системе 20 масс. %. При этом обеспечивается максимальное значение скорости фильтрования суспензии 0,537 м³/(м²·ч), что в 1,08 и 1,03 раз выше в сравнении с фильтрованием суспензий, содержащих сульфат аммония и серную кислоту, соответственно. Выявленная тенденция распространяется на скорость промывки осадков - максимальное значение соответствует 0,750 м³/(м²·ч), что превосходит соответствующие образцы сравнения в 1,1 и 1,15 раз. Для цитирования: Почиталкина И.А., Кондаков Д.Ф., Макаев С.В., Сибирякова И.Б., Костанов И.М. Сульфатные добавки для интенсификации фильтрации низкосортной фосфоритно-азотнокислой суспензии. Изв. вузов. Химия и хим. технология. 2022. Т. 65. Вып. 12. С. 30-36. DOI: 10.6060/ivkkt.20226512.6672.

This work is aimed at investigating a new process of film distillation with a membrane condenser (FDMC) for obtaining fresh water from a reverse osmosis concentrate. The behavior of a number of structural materials during their exposure for 4.5 months in the open air and in sea water has been investigated. In the Simulink/MATLAB program, a model of the FDMC unit with the possibility of using solar radiation as a renewable energy source has been built. The operation of the unit for one month was simulated and it was shown that the area of solar collectors has the greatest influence on the volume of water received during a month of operation. The area of the evaporator has little effect on the overall process performance, but it can reduce the initial costs while maintaining the same payback period. Modeling showed that the recovery of distilled water decreases by 2–3% (from ~71–72 to ~69%) with a decrease in the NaCl concentration of the output stream from 26 to 24 wt %. The mode with a lower concentration of the output solution was found to be optimal due to the absence of both the risk of pipeline clogging and the need for frequent flushing of the evaporating surface. The use of data on solar radiation for the most and least sunny months (April and November, respectively) shows a nonlinear drop (by 46–47%) in productivity for water, which is explained by both nonlinearity of the temperature dependence of water vapor pressure and a nonlinear relationship between the solar collector efficiency and radiation intensity and ambient temperature. Varying the temperature of the cold circuit shows that using a lower temperature increases the water productivity by 5–15%, while keeping the water recovery rate constant.

The influence of hyper-crosslinked polystyrene (HCPS) Macronet^TM MN200 on the gas transport properties and aging of the highly permeable glassy polymer poly(1-trimethylsilyl-1-propyne) (PTMSP) was studied and analyzed in detail. The gas transport characteristics of dense PTMSP membranes containing 0–10.0 wt % HCPS were studied. It was shown that the introduction of a small amount of HCPS into the PTMSP matrix led to a 50–60% increase of the permeability coefficients of the material for light gases (N₂, O₂, CO₂) and slowed down the deterioration of polymer transport properties over time. The lowest reduction in gas permeability coefficients (50–57%) was found for PTMSP containing HCPS 5.0 wt % after annealing at 100 °C for 300 h. It was found that HCPS sorbed residues of tantalum-based polymerization catalyst from PTMSP. In order to investigate the influence of catalysts on transport and physical properties of PTMSP, we purified the latter from the polymerization catalyst by addition of 5 wt % HCPS into polymer/chloroform solution. It was shown that sorption on HCPS allowed for almost complete removal of tantalum compounds from PTMSP. The membrane made of PTMSP purified by HCPS demonstrated more stable transport characteristics compared to the membrane made of the initial polymer. HCPS has a complex effect on the aging process of PTMSP. The introduction of HCPS into the polymer matrix not only slowed down the physical aging of PTMSP, but also reduced chemical aging due to removal of active reagents.

This article describes a new technique for the preparation of hollow fiber (HF) membrane samples using an automatic manipulator unit. The manipulator uses a syringe needle to form a HF of a given geometry. The needle in automatic mode is sequentially immersed, first into the polymer solution and then into the coagulation bath. The possibility of using a manipulator to obtain HF samples was studied on the known polysulfone (PSf)/N-methylpyrrolidone (NMP)/pore-forming additive system. A series of HF membrane samples were made within 29 h from twelve 1 mL PSf casting solutions. This was 15 times faster than obtaining samples of HF membranes at the multifunctional research laboratory facility. From the point of view of the consumption of the components of the casting solution, the use of the manipulator was 30 times more economical, and the consumption of water for precipitation and washing was 8000 times less. The developed method made it possible to study samples of HF by scanning electron microscopy (SEM), ultrafiltration, and evaluate its mechanical properties without spinning the membranes. Using the new technique, the optimal composition of the casting solution for the wet spinning of HF PSf membranes was selected during two weeks. Thus, the manipulator makes it possible to significantly reduce the time of the new membrane preparation, reduce the volume of used polymer, and thus makes it promising to study expensive or new membrane materials.