Centrifugal Concentrators Research Articles

The avidity of virus-specific antibodies obtained from <i>in vitro</i> stimulated memory b cells does not change one month after booster with Sputnik V or Comirnaty

The protective properties of long-term immunological memory after vaccination against COVID-19 are characterized by the neutralizing activity of serum antibodies and antibodies secreted by memory B cells upon repeated encounter with the antigen. Somatic hypermutations occurring in the immunoglobulin genes of memory B cells are one of the mechanisms for increasing the affinity of antibodies. At the moment, the effect of booster vaccination against COVID-19 with vector vaccines, on the maturation of memory B cells remains poorly understood. The purpose of this work was to determine how COVID-19 booster affects the affinity of RBD-specific IgG antibodies secreted by memory B cells. B lymphocytes were isolated from peripheral mononuclear blood cells of volunteers who had been revaccinated against COVID-19 with Sputnik V or Comirnaty. B cells were stimulated in vitro with CD40L expressed on the surface of A549 feeder cells and IL-21. Supernatants were concentrated 8-fold using centrifugal concentrators. In the obtained supernatants from stimulated memory B cells, the level of IgG antibodies specific to wild-type RBD was determined by enzyme-linked immunosorbent assay (ELISA). To determine the avidity index, ELISA with 7M urea was provided. It was shown that despite a general increase in the amount of antigen-specific IgG antibodies obtained from stimulated memory B cells, there was no change in the avidity of these antibodies one month after booster in both groups of donors. The obtained results contribute to the understanding of the mechanisms of memory B cell maturation after booster vaccinations against COVID-19 and may be useful for deciding on the strategy of booster vaccination.

Diagnostics of preeclampsia based on Congo red binding to urinary components: Rationales and limitations.

Preeclampsia is a disorder that can occur during pregnancy and is one of the leading causes of death among pregnant women. This disorder occurs after the 20th week of pregnancy and is characterized by arterial hypertension, proteinuria, fetoplacental, and multiple organ dysfunctions. Despite the long history of studying preeclampsia, its etiology and pathogenesis remain poorly understood, and therapy is symptomatic. One of the factors of the disorder is believed to be misfolded proteins that are prone to form amyloid aggregates. The CRD tests, utilizing the binding of the amyloid-specific dye Congo red to urine components, demonstrate high efficiency in diagnosing preeclampsia. However, these tests have also been found to be positive in other disorders with proteinuria, presumably associated with concomitant amyloidosis. To assess the limitations of the CRD tests, we examined urine congophilia and protein components mediating Congo red positivity in patients with proteinuria, including preeclampsia, amyloid and non-amyloid nephropathies. We stained the urine samples and calculated congophilia levels. We also assessed the contribution of large protein aggregates to congophilia values using ultracentrifugation and determined the molecular weights of congophilic urinary proteins using centrifugal concentrators. All proteinuric groups demonstrate positive results in the CRD tests and congophilia levels were more than two times higher compared with the control non-proteinuric groups (p <0.01). There was a strong correlation between urine protein excretion and congophilia in amyloid nephropathy (rs = 0.76), non-amyloid nephropathies (rs = 0.90), and preeclampsia (rs = 0.90). Removal of large aggregates from urine did not affect the congophilia levels. Separation of urine protein fractions revealed congophilic components in the range of 30-100 kDa, including monomeric serum albumin. Our results indicate limitations of CRD tests in preeclampsia diagnostics in women with renal disorders and underscore the need for further research on the mechanisms of Congo red binding with urine components.

Parameter Optimization of the Separation Process for Hematite and Quartz Mixture Minerals Based on a Cyclone Centrifugal Separator

The current centrifugal concentrators do not continuously concentrate heavy minerals of large mass weight—for example, in the processing of iron oxides. A cyclone centrifugal separator is a new type of beneficiation equipment that has been developed on the basis of the principles of centrifugal separation and hydrocyclones. In this study, a cyclone centrifugal separator was used for the beneficiation of a hematite–quartz mixture, and the separation effect under different operating conditions was analyzed. The results showed that various factors, such as the feeding concentration, the feeding pressure, and the number of fluidization holes in the separation cone, had a significant influence on the separation performance of the cyclone centrifugal separator. The single-factor separation test results showed that the appropriate operating conditions were a feeding concentration of 10%, a feeding pressure of 120 kPa, a 40-hole separation cone, a settling port pressure of 70 kPa, and an overflow port pressure of 50 kPa. The results of the open circuit separation test that was designed on the basis of the single-factor experiment showed that the concentrate grade of Fe in the hematite–quartz mixture, with 44.12% Fe, was 54.42% after beneficiation, indicating better beneficiation separation effects. This study provides a new approach for the beneficiation of a large number of difficult-to-select hematite ores in China, and can provide a reference for the further expansion and application of the cyclone centrifugal separator in the field of mineral processing.

Mathematical model of using CVD technology

ABSTRACT The relevance of the research is due to the acquisition of new knowledge about the optimization of the technological parameters of the operation of centrifugal concentrators using Knelson CVD technology, namely: setting the valve opening frequency and the time during which the valves remain open. The purpose of the research: statistical analysis of the results of pilot studies of the applicability of the Knelson CVD technology on various products of the plant, using the method of group consideration of arguments, to obtain the dependencies between the output of the concentrator and the adjustable parameters, allowing to carry out preliminary calculations on the effectiveness of the implementation of this technology at enrichment enterprises. In this work, we used regression analysis methods aimed at building statistically significant models, as well as the method of group consideration of arguments, which allows you to build many similar models and tune them. The novelty of the work lies in the application of the method of group consideration of arguments in order to generate families of mathematical models and choose the optimal one.

Evaluation of the effectiveness of modified CRD tests in the diagnosis of preeclampsia

BACKGROUND: Preeclampsia is a multisystem complication of pregnancy associated with an increased risk of maternal / perinatal morbidity and mortality. In this regard, the development and following improvement of low-cost and convenient methods for diagnosis of preeclampsia is essential for accurate prediction, quick confirmation of the diagnosis and convenient monitoring of the pathology.&#x0D; AIM: The aim of this study was to optimize a preeclampsia diagnosis test system based on the binding of proteins to the Congo red dye (CRD test).&#x0D; MATERIALS AND METHODS: The study used 70 urine samples obtained from patients diagnosed with preeclampsia (n = 25) and from non-preeclampsia pregnant women (n = 45). The samples were stained with Congo red and the dye retention in the sample on the membrane after washing was calculated. Before staining, protein concentrations in the urine samples were equalized using centrifugal concentrators or the samples were used with the original protein concentrations. To wash the samples from the unbound dye, either methanol or ethanol was used. To compare the effectiveness of four CRD test variants differing in sample preparation, staining, and washing, ROC analysis was performed (IBM SPSS Statistics 20 software).&#x0D; RESULTS: The express CRD test was designed as an optimization of the conventional CRD test. The effectiveness of the express test (the area under the ROC curve being 0.9) was higher than that of the other three test options (the area under the ROC curve ranges from 0.67 to 0.82). The developed express CRD test can provide 95% specificity and 73% sensitivity, which indicates the promise of using this method in clinical diagnostics for the specific detection of preeclampsia patients.&#x0D; CONCLUSIONS: Optimization of the CRD test has provided more effective protocols for diagnosis of preeclampsia from urine samples using Congo red (express CRD test) and has simplified the routine application of this test in clinical practice.

Methodology for applying control theory in modeling the processes of centrifugal enrichment of mineral raw materials

ABSTRACT The article discusses an approach aimed at the formation of a methodology for applying the principles and models used in the automatic control theory in relation to the processes of enrichment of mineral raw materials. The problem solved in the article is posed as follows, try to represent the process of gravitational enrichment, namely centrifugal concentration, in the form of a transfer function and try to find its parameters. The paper proposes an approach to modeling centrifugal concentrators based on transfer functions, using averaged values of output characteristics. Proposal of a mechanism for determining the parameters of transfer functions and their calculation based on experimental data. To check the presented calculations, the MatLAB software tool with the Simulink package was used. As a result, the transfer function of the KC-CVD6 apparatus used in the gold deposit was found and satisfactory results were obtained. The work uses methods of identification of automatic systems, methods of system analysis, as well as methods of mathematical modeling, namely the numerical solution of differential equations, implemented in the MatLAB environment with the Simulink package. A comparison with the classical regression model was made; as a result, the modeling error was reduced by two times. The simulation error for the concentrate yield was less than 1%.

Моделирование процесса центробежной сепарации минеральных частиц в гравитационном поле с применением метода конечных элементов

The article discusses gravity concentration using centrifugal separators. It describes the design and operating principle of centrifugal separators. A method to loosen the mineral bed by a water jet is considered and the concentration process in the centrifugal concentrator rotor is analyzed. The paper presents a way to optimize the gravity enrichment processes through modeling of the centrifugal separation based on the finite element method. The subject matter of the finite element analysis is described. The main advantages in application of centrifugal concentrators and prospective ways to improve their performance are described. A description of economic efficiency for the companies in using these concentrators is provided.

Modelling of continuous centrifugal gravity concentrators using a hybrid optimization approach based on gold metallurgical data

Conventional optimization procedures for Continuous Centrifugal Gravity Concentrators (CCGCs) impose a priori weighting on objectives and results in a single optimum point, thereby failing to exploit the competing grade/recovery relationship. To generate an optimum operating line rather than a conventional optimization approach, a non-dominated recovery/grade line has been developed using a novel multivariate optimization technique code. The goal is to simultaneously maximize both grade and recovery objectives. This optimization has been developed and tested using a Knelson Continuous Variable Discharge concentrator, CVD on flotation tailings of a metallic sulphide ore (0.7 g/t Au), without a priori weighting of the competing objectives. This paper outlines the developed technique, which is an iterative hybrid performance improvement approach that exploits Pareto’s non-dominated approach to multi-objective optimization, for determining the operating curve for CCGCs. This work is entirely and directly based on gold metallurgical data (i.e. Au recovery and grades) rather than an indirect proxy to generate the optimum operating line for the Knelson CVD. As a part of the suggested approach, the Artificial Neural Network (ANN) simulation has been effective in predicting the CVD performance: for the experimental and ANN simulated results, correlation coefficients are 0.92 and 0.81 for the Au upgrade ratio and Au recovery, respectively. The prediction level of the Regression Model was acceptable for the Au recovery (R2 = 0.78) and good for the Au upgrade ratio (R2 = 0.88). Based on these, the developed Pareto solution and the hybrid optimization model also enabled significant prediction of CCGC performance: at different operational conditions Au recoveries predicted by the Pareto optimum solution (11–32%) correlated well with experimental results (9–26%). Further, the method enables assessment of the level of influence of operational parameters on the metallurgical outcomes, hence identification of an optimum grade vs. recovery operating line. Overall, the results demonstrate the robustness of the approach in optimization of CCGCs operation despite trace occurrence of Au. Suggested approach is highly reliable for tuning multi operation variables of CCGCs to enable operation of these unique machines to yield successful concentration performance in plant scale.

A study of the thickening process for fine tailings of gold-bearing ores

Refractory low-grade gold-bearing ores require deep processing with finer preliminary grinding. As a result, finely dispersed products are formed, including fine tailings, which raise particular environmental concerns. The article presents the results of experimental thickening studies for the concentration tailings of gold-bearing ores from the Yuzhno-Nevyanskoe and Panovskoe deposits. The material studied is distinguished by the presence of fine clay inclusions, which reduce the sedimentation rate of slurry solids. The main processing methods are gravity separation in centrifugal concentrators and flotation. Electrokinetic properties of the particle surface, in particular, the x-potential, in the tailings slurries entering the thickening process may be used to predict thickening performance with sufficient accuracy and significantly reduce the number of laboratory experiments. Measured values of the x-potential, electric double layer thickness, and other dielectric properties of the particle surface were used to establish that the most effective sedimentation of the tailings was achieved at a mass fraction of solids in the slurry of up to 25 % and a pH value of at least 10.5. The optimal flocculant feed amount required to increase the slurry sedimentation rate was also established. It is therefore recommended to use the following flocculants for the ore processing tailings of the Yuzhno-Nevyanskoe deposit: Praestol 2510 at more than 10 g/t and Magnaflok 10 at over 20 g/t. Flocculants are not required for thickening the ore processing tailings of the Panovskoe deposit.

Recovery of Rare Earth Oxides from Flotation Concentrates of Bastnaesite Ore by Ultra-Fine Centrifugal Concentration

Historically, the ability to effectively separate carbonate gangue from bastnaesite via flotation has frequently proven to be challenging without sacrificing significant rare earth oxide (REO) grade or recovery. However, in light of the fact that the rare earth bearing minerals often exhibit higher specific gravities than the carbonate gangue, the possibility exists that the use of gravity separation could be used to achieve such a selective separation. This however is complicated by the fact that, in cases such as this study when the liberation size is finer than 50 microns, most traditional gravity separation methods become increasingly challenging. The aim of this study is to determine the applicability of centrifugal concentrators to beneficiate ultra-fine (UF) bastnaesite and calcite bearing flotation concentrates. By using a UF Falcon, it was possible to achieve initial gravity REO recoveries exceeding 90% while rejecting on the order of 25% to 35% of the total calcium from an assortment of rougher and cleaner flotation concentrates. Additionally, when additional stages of cleaner UF Falcon gravity separation were operated in an open circuit configuration, it was possible, from an original fine feed of 35 microns containing 50.5% REO and 5.5% Ca, to upgrade up to approximately 59% REO and 2.0% calcium. While not the goal of this study, these results also support previous limited data to suggest that UF Falcons are potentially capable of treating a wider range of materials than they were originally designed for, including feeds rich in heavy mineral content.

Model of baddeleyite recovery from dump products of an apatite-baddeleyite processing plant using a CVD6 concentrator

The paper is devoted to developing a model of baddeleyite recovery from dump products of an apatite-baddeleyite processing plant using centrifugal concentrators. The relevance of the work arises from the acquisition of new knowledge on the optimization of technological parameters of centrifugal concentrators using Knelson CVD (continuous variable discharge) technology – in particular, setting the frequency of valve opening and the duration of valves remaining open. The purpose of the research was to assess the applicability of CVD technology in the treatment of various dump products of the processing plant and to build a model of dependencies between the concentrate and tailings yields and the adjustable parameters, which will allow to perform preliminary calculations of the efficiency of implementing this technology at processing plants. The research objects are middling and main separation tailings of the coarse-grained stream and combined product of main and recleaner separation tailings of the fine-grained stream. The study uses general methods of mathematical statistics: methods of regression analysis, aimed at building statistically significant models, describing dependence of a particular variable on a set of regressors; group method of data handling, the main idea of which is to build a set of models of a given class and choose the optimal one among them. Authors proposed an algorithm for processing experiment results based on classical regression analysis and formulated an original criterion for model selection. Models of dependencies between the concentrate and tailings yields and the adjustable parameters were built, which allowed to establish a relationship between the concentrate yield and the valve opening time, as well as a relationship between the tailings yield and the G-force of the installation.

Динамическое моделирование подвижности минеральной постели в центробежных концентраторах

The article discusses a method for determining the effective parameters of centrifugal concentrators with fluidization of a mineral bed with water through holes in the walls of a rotating cone. The device and the principle of operation of a laboratory setup for studying the constrained movement of mineral particles in a centrifugal field are described. Also, the optimization of the degree of loosening of the mineral bed in the centrifugal concentrator is considered. It was established experimentally that with existing water flow rates the condition of the mineral bed was close to the pressed state. Using the developed method of optimizing the ratio of water pressure in the fluidization system and the separation factor, the optimum water pressure and its flow rate were calculated in laboratory conditions. As a result, it was possible to raise the extraction during the first stage of gravity concentration by 2%. Therefore, it was determined that the degree of loosening depends on the correlation of the separation factor and the water pressure in the fluidization system. Based on the proposed approach, it is possible to develop an automation system to adjust the parameters of the centrifugal concentrators. Based on the results of calculating the balance of the concentration process in the gold extraction plant at the Kedrovskoe deposit, it was established that the application of the proposed methodology helped to improve the efficiency of the centrifugal free-flow concentrator.

Predicting intra-articular residence time of hyaluronan-based viscosupplements. a comparison between human and artificial synovial fluid as degradation media

Purpose: Hyaluronan(HA)-based viscosupplements, although resorbable, present different in vivo residence times, which are mainly related to structural modifications of the native polymer. The residence time of unmodified HA generally does not exceed 5 days, while chemically crosslinked HA can be detected in the joint up to one month. Artificial synovial fluid (ASF) have been described in the literature to mimic rheology of or drug release in human SF (SF). These models suffer from a limitation from the biological point of view: the absence of hyaluronidases, HA degrading enzymes expressed by the chondrocytes in contact with SF, well described in literature. A novel in vitro preparation of ASF with hyaluronidase is hereby reported and tested with three marketed viscosupplements: Sinovial® HL (SHL, IBSA Farmaceutici), which contains native HA of both low and high MW, Hyalubrix® (HBX, Fidia Farmaceutici S.p.A.), which contains unmodified high MW HA and Hymovis® (HYM, Fidia Farmaceutici S.p.A.), composed of HA modified with hexadecyl alkyl chains via amidic bonds (MW comprised between 500 and 700 kDa). The effect of this ASF towards HA molecular weight and rheological properties was reported and compared with the degradation profile in centrifuged human SF. Methods: ASF was formulated with the following composition: NaCl 8 g/L, KCl 0.2 g/L, Na2HPO4 1.7 g/L, Bovine Serum Albumin (BSA) 19 g/L, Bovine Testes Hyaluronidase (BTH) 6 U/mL, Gentamicin 0.01 mg/mL (pH 7.4). The salt and BSA composition and concentration in SF are well reported in the literature. At the best of our knowledge, the quantification of hyaluronidase activity in human SF is not reported. Considering that Hyaluronidase (Hyal) activity titrated in serum is at least 6 U/mL in BTH equivalent, and that Hyal (MW 55-60 kDa) can permeate synovial membrane, the same concentration of BTH was added to artificial SF. Centrifuged (cell free) human SF collected from OA patients was used as “degradation media”. Sinovial® HL, Hyalubrix® and Hymovis® were separately incubated either in ASF or SF at 37 °C for 14 days at a w/w ratio of approximately 1:1, under mild shaking. At different time points (0, 1, 7 and 14 days) the viscoelastic moduli and dynamic viscosity of the mixtures were measured with an Anton Paar MCR 92 rheometer. Moreover, at each time point the mixtures were diluted in water and filtered through Merck Vivaspin® 2 centrifugal concentrators (MWCO = 100 kDa, comparable to the synovial membrane cut-off) in order to quantitate the permeated and retained HA fractions. PBS+SF at a w/w ratio of 1:1 was used as blank for HA measurement. The percent recovery of the HA fraction with MW ≤ 100 kDa was determined by SEC-TDA (Omnisec Resolve/Reveal, Malvern instruments). Results: The degradation profile of HYM, HBX and SHL in SF or ASF is shown in the graph below: after 14 days the viscoelasticity (expressed as storage modulus: G’) of HYM/SF, HBX/SF and SHL/SF is slightly decreased; however, the elasticity of all viscosupplements in ASF is completely impaired after only few hours. After 14 days, the percent recovery of high MW HA (>100 kDa) confirms the rheological data: in SF, HYM, HBX and SHL were not depolymerized to low MW polymers while, in ASF, the percent recovery in higher MW HA was only about 45%, 10% and 13% for HYM, SHL and HBX respectively. The strong depolymerizing activity of ASF was confirmed for all the viscosupplements tested; nonetheless, HYM showed higher resistance to degradation in ASF compared to SHL. Conclusions: In this work, two different in vitro and ex vivo models were compared in order to predict the in vivo residence time of three HA-based viscosupplements in the intra-articular environment. Based on the literature, after a single intra-articular administration of high MW HA (2000 kDa), the measured residence time was as short as about 5 days. The ex vivo model with centrifuged human SF bears the limitation of the absence of hyaluronidases (a cell surface glycosylphosphatidylinositol-anchored protein, removed with the chondrocytes during the centrifugation process), while the assay in ASF added with BTH turned out to be more reliable and can therefore be employed during viscosupplement development to predict the intra-articular residence time of HA-based products

Analysis of the processing mechanism in a centrifugal concentrator with a horizontal axis of rotation

This scientific work presents the results of comparative tests of centrifugal concentrators with a vertical and horizontal axis of rotor spinning. The article also describes a qualitative analysis of the behavior of mineral particles in a centrifugal field with fluidization for concentrators with a horizontal axis. The experiment demonstrated that concentrators with a horizontal axis are not inferior in terms of the qualitative recovery indicators to concentrators with a vertical axis. The researches also provided facts about the wide practical application of concentrators with a horizontal rotor arrangement.

Assessment of Gravity Dressability of Gold Ore - GRG Test

Gravity methods are widely used for processing of gold ores. But many aspects of these processing techniques require improvement. In the study, methods of fire assay, gravimetric, chemical, mineralogical analyses of gold ores were used. In terms of sulfide sulfur content and degree of sulfur oxidation, the gold ore is assigned to the low-sulfide type of ore in the primary zone. Mineralogical analysis showed the ore-bearing rock is represented by phyllite. Gold in the ore occurs mainly in the form of free large and fine particles. The fine gold is closely associated with pyrite. GRG test was carried out for assessing gravity dressability of the gold ore. The total gold recovery is more than 41 %. The highest gold recoveries were achieved at the first stage at 100 % of -1.6 mm ore grain size, and at the third stage at 80 % of -0.071 mm ore grain size. This indicates that both relatively large gold and fine free gold particles are present in the ore. This is also confirmed by mineralogical analysis. The GRG test results showed that the gold ore can be effectively concentrated using centrifugal concentrators. The level of gold recovery by gravity at the multi-stage ore grinding is quite high. When developing the ore concentration process flow sheet, gravity separation in centrifugal concentrators should be included.

Concentration of viruses and electron microscopy.

Nearly all lethal viral outbreaks in the past two decades were caused by newly emerging viruses. Viruses are often studied by electron microscopy (EM), which provides new high-resolution data on the structure of viral particles relevant to both fundamental virology and practical pharmaceutical nanobiotechnology. Electron microscopy is also applied to ecological studies to detect viruses in the environment, to analysis of technological processes in the production of vaccines and other biotechnological components, and to diagnostics. Despite the advances in more sensitive methods, electron microscopy is still in active use for diagnostics. The main advantage of EM is the lack of specificity to any group of viruses, which allows working with unknown materials. However, the main limitation of the method is the relatively high detection limit (107 particles/mL), requiring viral material to be concentrated. There is no most effective universal method to concentrate viruses. Various combinations of methods and approaches are used depending on the virus and the goal. A modern virus concentration protocol involves precipitation, centrifugation, filtration, and chromatography. Here we describe the main concentrating techniques exemplified for different viruses. Effective elution techniques are required to disrupt the bonds between filter media and viruses in order to increase recovery. The paper reviews studies on unique traps, magnetic beads, and composite polyaniline and carbon nanotubes, including those of changeable size to concentrate viral particles. It also describes centrifugal concentrators to concentrate viruses on a polyethersulfone membrane. Our review suggests that the method to concentrate viruses and other nanoparticles should be chosen with regard to objectives of the study and the equipment status of the laboratory.

УСТАНОВЛЕНИЕ ТЕХНОЛОГИЧЕСКИХ ЗАВИСИМОСТЕЙ РАБОТЫ КОНЦЕНТРАТОРА KC-CVD6 С ПОМОЩЬЮ МЕТОДА ГРУППОВОГО УЧЕТА АРГУМЕНТОВ

Актуальность исследования обусловлена получением новых знаний об оптимизации технологических параметров работы центробежных концентраторов, эксплуатируемых по технологии Knelson CVD, а именно: настройка частоты открытия клапанов и время, в течение которого клапаны остаются открытыми. Цель: статистический анализ результатов полупромышленных исследований применимости технологии Knelson CVD на различных продуктах фабрики с помощью метода группового учета аргументов для получения зависимостей между выходом концентра и настраиваемыми параметрами, позволяющими проводить предварительные расчеты по эффективности внедрения данной технологии на обогатительных предприятиях. Объекты: продукты, полученные в результате работы гидроциклонов, а также технологические параметры работы центробежных концентраторов. Методы: общие методы математической статистики, в частности методы регрессионного анализа, направленные на построение статистически значимых моделей, описывающих зависимость какой-либо переменной от множества регрессоров. Также, наряду с классическим аппаратом регрессионного анализа, применяется метод группового учета аргументов, основная идея которого заключается в построении множества моделей заданного класса и выборе среди них оптимальной. Результаты. Разработана эффективная методика обработки результатов тестов, проведенных на обогатительном оборудовании, базирующаяся на методе группового учета аргументов. На основании полученных данных построены статистически значимые модели, описывающие зависимость содержания в хвостах и концентратах по ценным компонентам от различных настраиваемых параметров оборудования, обоснована их эффективность, позволяющая применять данные модели в дальнейших исследованиях по применению CVD технологии. Продемонстрировано применение метода группового учета аргументов на примере построения полиномиальных регрессионных моделей, содержащих нелинейные комбинации регрессоров.

High-throughput conventional and stealth cationic liposome synthesis using a chaotic advection-based microfluidic device combined with a centrifugal vacuum concentrator

Microfluidics is an emerging technology that allows efficient mixing of fluids on the nanoliter scale and has recently been employed for the production of lipid-based systems. In this study, we investigated the manufacturing of conventional (EPC/DOTAP/DOPE) and stealth (EPC/DOTAP/DOPE/DSPE-PEG(2000)) cationic liposomes (CLs) in a high-throughput chaotic advection-based microfluidic device (CA-MD) using water and ethanol. We assessed the effects of total flow rate (TFR), flow rate ratio (FRR), and flow configuration on CL formation. We compared the results with properties of CLs produced on a diffusion-based microfluidic device (D-MD). FRR (aqueous/solvent ratio) values were found to have a strong correlation with vesicle formation and values close to 1 led to the production of conventional and stealth CLs with diameter and polydispersity indices close to 200 nm and 0.2, respectively. Both liposomes are unilamellar, and stealth CL production could minimize micelle formation and operate at high flow velocities without altering characteristics of CLs. These findings were supported with dynamic light scattering (DLS), cryo-transmission electron microscopy (Cryo-TEM), and synchrotron small angle X-ray scattering (SAXS) techniques. The high solvent content in liposomes after microfluidic synthesis (FRR = 1) was reduced by employing centrifugal vacuum concentrators (CVC) at low pressure and 43 °C as an alternative distillation process for successful ethanol removal without changing the structural properties of these nanoaggregates. Finally, both CLs were able to transfect pDNA into PC-3 cancer cells. The CA-MD coupled to a CVC technique produced conventional and stealth CLs with high productivity, which makes it readily applicable for industrial production.

An optimized method for counting viral particles using electron microscopy

Viruses can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea. When studying samples containing viruses, one confronts an unavoidable question of the quantitative determination of viral particles in the sample. One of the simplest and efficient approaches to quantitative determination of viral particles in preparation includes the use of electron microscopy; however, a high detection threshold is a significant limitation of this method (107 particles per ml). Usually, such sensitivity is insufficient and can result in error diagnosis. This study aims to develop a method making it possible to detect the number of viral particles more precisely and work with samples in which the concentration of particles is lower than 107/ml. The method includes a concentration of viral particles on the polyethersulfone membrane applied in centrifugal concentrators and subsequent calculation using an electron microscope. We selected env-pseudoviruses using a lentiviral system making it possible to obtain standardized samples of virus-like particles that are safer than a live virus. Suspension of viral particles (a volume of 20 ml) was placed into the centrifugal concentrator and centrifuged. After that, we took a membrane out of the centrifugal concentrator and evaluated the number of particles on the ultrathin section using an electron microscope. The number of viral particles on the whole surface of the filter (a square of 4 сm2) was 4×107 virions, the initial concentration of pseudoviruses in the sample was 2×106 per 1 ml (4×107 particles per 20 ml). As a result, the developed method enables one to evade the major disadvantage of quantitative determination of viruses using electron microscopy regarding a high detection threshold (concentration of particles 107/ml). Furthermore, the centrifugal concentrator makes it possible to sequentially drift a considerable volume of the suspension through the filter resulting in enhancement of test sensitivity. The developed approach results in increased sensitivity, accuracy, and reproducibility of quantitative analysis of various samples containing animal, plant or human viruses using electron microscopy.

Thrombin inhibitor from the salivary gland of the camel tick Hyalomma dromedarii.

Blood-sucking arthropods have different types of anticoagulants to allow the ingestion of a blood meal from their hosts. In this study, five anticoagulants prolonging the activated partial thromboplastin time were resolved from the salivary gland crude extract of the camel tick Hyalomma dromedarii by chromatography on diethylaminoethyl (DEAE)-cellulose column. They were designated P1, P2, P3, P4 and P5 according to their elution order. P5 was found to be a potent thrombin inhibitor and purified by ultrafiltration through two centrifugal concentrators of 50 and 30kDa molecular weight cut-off (MWCO), respectively. The camel tick salivary gland thrombin inhibitor was purified 60.6 folds with a specific activity of 564units/mg protein. It turned out to be homogenous on native-PAGE with molecular weight of 36kDa as detected on 12% SDS-PAGE. It inhibits bovine thrombin competitively with K i value of 0.55μM. A task for the future will be the elucidation of this thrombin inhibitor structure to allow its application in thrombosis treatment.