OBJECTIVES:Advances in improving existing noninvasive optical diagnostic methods and creating new criteria for assessing the effects of diabetes on tissues and the vascular system are highly demanded. One of the promising, noninvasive and contactless methods for visualizing the vascular system is laser speckle contrast imaging. This study studies the possibility of using magnetic resonance contrast agents in laser speckle contrast imaging and optical coherence tomography, for the first time, on rat ears, under conditions of alloxan-induced type 1 diabetes. By combining diagnostic techniques, the study investigated the ability to differentiate between healthy rat tissue and diabetic rat tissue based on dynamic and structural changes caused by local application of magnetic resonance agents. METHODS:This study explores the possibility of using magnetic resonance contrast agents for laser speckle-contrast imaging and optical coherence tomography of rat ears under conditions where alloxan-induced type 1 diabetes mellitus is developing was studied for the first time. RESULTS:Kinetics of scattering coefficient (µs) for healthy and diabetic rats during optical clearing were evaluated. The most significant reduction is seen with the Gadovist solution, showing decreases of 18.6% and 16.1% for healthy and diabetic rats, respectively. Magnevist induced a smaller reduction in the µs, with decreases of 12.6% and 6.8%, respectively. Data on the flow rate in the vessels of the ears of laboratory rats obtained in the diabetic group demonstrate reduced indicators, relative to the healthy group of animals. CONCLUSIONS:These results confirm the effectiveness of magnetic resonance contrast agents as optical clearing agents for both optical coherence tomography and laser speckle contrast imaging. For the first time, the nature of the change in the contrast of the static part with a change in scattering was studied. This is an additional application for studying the efficiency of optical clearing, and contributes to the multimodal application of speckle imaging methods.

Albumin microbubbles (MB) were among the first ultrasound (US) contrast agents used clinically. However, they are believed to contain denatured protein motifs, which compromise their stability, hence, limit their diagnostic and therapeutic utility. This study investigates the protein integrity, cavitation dynamics during US-assisted synthesis, and blood microrheology of albumin MB to better understand and improve their performance. Using bovine serum albumin as the shell material, we found that complexation with either a small molecule or macromolecular additive increased MB yield and enhanced acoustic stability. Spectroscopic analysis showed that MB shell formation favors protein structures close to the native state, while more severely altered fractions remain excluded from the shell. High-speed imaging and cavitation activity profiling revealed that additive-containing solutions suppressed cavitation activity while promoting the formation of sub-50 µm MB precursors under synthesis-mimicking conditions, leading to higher MB concentrations. Blood microrheology tests confirmed that albumin-copolymer MB had minimal impact on red blood cell deformability, aggregation, and critical shear stress, while in vivo cardiac US imaging showed their strong echogenicity lasting over 5 min post-injection. Together, these findings highlight how fine-tuning MB shell composition ‒ combined with structural and functional evaluation ‒ advances the understanding needed to improve albumin MB application potential. STATEMENT OF SIGNIFICANCE: This work provides integrated analysis of albumin-coated microbubbles, correlating protein structural integrity, synthesis dynamics, and blood microrheology. By combining spectroscopy, high-speed imaging, and rheological profiling, we demonstrate that rational additive selection enables microbubble formulations with enhanced acoustic stability, supported by in vivo cardiac ultrasound imaging. Notably, we show that microbubble formation favors albumin molecules retaining structures close to the native state, challenging the prevailing assumption that albumin shells are irreversibly denatured during synthesis. These findings provide a basis for designing structurally stable protein-coated microbubbles for effective ultrasound use.

In this study, fluorescence recovery after photobleaching (FRAP) experiments were performed on RBC labeled by lipophilic fluorescent dye CM-DiI to evaluate the role of adenylyl cyclase cascade activation in changes of lateral diffusion of erythrocytes membrane lipids. Stimulation of adrenergic receptors with epinephrine (adrenaline) or metaproterenol led to the significant acceleration of the FRAP recovery, thus indicating an elevated membrane fluidity. The effect of the stimulation of protein kinase A with membrane-permeable analog of cAMP followed the same trend but was less significant. The observed effects are assumed to be driven by increased mobility of phospholipids resulting from the weakened interaction between the intermembrane proteins and RBC cytoskeleton due to activation of adenylyl cyclase signaling cascade.

Blood microrheology depends on the constituents of blood plasma, the interaction between blood cells resulting in red blood cell (RBC) and platelets aggregation, and adhesion of RBC, platelets and leukocytes to vascular endothelium. The main plasma protein molecule -actuator of RBC aggregation is fibrinogen. In this paper the effect of interaction between the endothelium and RBC at different fibrinogen concentrations on the RBC microrheological properties was investigated in vitro. Laser tweezers were used to measure the RBC-endothelium interaction forces. It was shown for the first time that the interaction forces between RBC and endothelium are comparable with the RBC aggregation forces, they increase with fibrinogen concentration and reach the saturation level of about 4 pN at the concentration of 4 mg/ml. These results are important for better understanding the mechanisms of RBC and endothelium interaction and developing the novel therapeutic protocols of the microrheology correction in different pathologies.

Erythrocyte aggregation plays a vital role in blood flow. This study demonstrates the effectiveness of laser-optical techniques in measuring erythrocyte aggregation parameters in healthy donors and patients suffering from different diseases.

The perfusion of tissues and blood flux strongly depend on several interdependent parameters, such as viscosity of blood, red blood cell aggregation and red blood cell deformation. In case of many blood disorders these parameters are altered. This pilot study aimed to investigate the relationship between whole blood viscosity and microrheological parameters in patients with essential thrombocythemia (ET), as well as to compare microrheological parameters in patients with ET, erythrocytosis and spherocytosis. Blood viscosity measurements were performed using a rotational viscometer, while microrheological parameters were assessed through laser aggregometry and laser diffractometry techniques. The findings revealed novel data of the correlation between whole blood viscosity and microrheological parameters of patients with ET. Overall, this study provides valuable preliminary evidence on the relationship between whole blood viscosity and microrheological parameters in the context of blood disorders.

The blood rheology in vitro in glass or plastic microfluidic chips is different from that in vivo in blood vessels with similar geometry. Absence of vascular endothelium is suggested to cause these discrepancies. This work aims to perform in vitro measurements of blood microrheologic parameters in a slit microfluidic channel covered with endothelial cells (HUVEC). The laser aggregometry was employed to measure the intensity of laser light, backscattered from the blood flow, as a function of shear stress to evaluate the hydrodynamic strength of red blood cells (RBC) aggregates in terms of critical shear stress (CSS). The results demonstrated a decrease in CSS accompanied by an increase in the accuracy of its measurement at similar shear stresses when endothelial cells were present in the channel. The findings hold valuable implications for advanced approaches for endothelization of microfluidic devices, facilitating the study of blood flow dynamics in physiologically more relevant environment.

In this study, the parameters of blood microcirculation and microrheology were measured using the methods of laser aggregometry and optical tweezers in vitro, as well as the method of digital capillaroscopy in vivo. It was shown that in patients suffering from type 2 diabetes mellitus, an increase in the number of RBC aggregates passing through the narrow capillaries leads to a significant decrease in the velocity of the capillary blood flow, which can be explained by the increased viscosity of the whole blood and decreased deformability of RBCs. Also, for the group of patients, a statistically significant increase in the rate of RBC aggregation and the hydrodynamic strength of aggregates, RBC aggregation and disaggregation forces were observed compared to the control group. We have demonstrated the possibility of using these methods to assess changes in microrheological and microcirculatory parameters of the blood.

In this work, the influence of optical clearing agents (OCA) on the blood flow in nailfold capillaries was studied. It was shown that parameters obtained by nailfold capillaroscopy technique depend on OCAs used for the visualization of capillaries.

We consider the issues of obtaining information about the distribution of red blood cells in size from the scattering pattern of a laser beam on a wet blood smear. Within this article it is assumed to calculate the first three moments of the size distribution. The analytical model of light diffraction by blood smears was developed, as well as numerical experiments for verification suggested approach were carried out. The possibility of calculating average diameter of erythrocyte, width and asymmetry of size distribution by analyzing the angular distribution of light intensity in the diffraction pattern was shown

The efficiency of 15 optical clearing agents (OCAs) that are widely used for enhancement of imaging of tissues was investigated. We show a significant impact on elevating the transparency and improving the visualization of the nail bed capillaries. A significant effect of OCAs on microrheological parameters of blood was shown.

Optical clearing agents (OCAs) are substances that temporarily modify tissue's optical properties, enabling better imaging and light penetration. This study aimed to assess the impact of OCAs on the nail bed and blood using in vivo and in vitro optical methods. In the in vivo part, OCAs were applied to the nail bed, and optical coherence tomography and optical digital capillaroscopy were used to evaluate their effects on optical clearing and capillary blood flow, respectively. In the in vitro part, the collected blood samples were incubated with the OCA and blood aggregation properties were estimated using diffuse light scattering techniques. The results indicate that OCAs significantly influence the optical properties of the nail bed and blood microrheology. These findings suggest that OCAs hold promise for improving optical imaging and diagnostics, particularly for nail bed applications, and can modify blood microrheology.

Red blood cell (RBC) aggregation as well as their deformation significantly affects blood microrheology. These processes depend on various factors, one of which is concentration of the nitric oxide, one of the main signaling molecule in the bloodstream. The purpose of this study was to investigate the effect of nitric oxide on the microrheological properties of red blood cells (RBCs) in RBC samples of various media after the addition of nitric oxide donor sodium nitroprusside in vitro. Microrheological properties were measured using laser aggregometer and ektacytometer based on diffuse light scattering and diffraction of laser light on a suspension of RBCs, respectively. The study found that heparin-stabilized blood showed increased RBC aggregation and deformation with sodium nitroprusside concentrations of 100, and 200[Formula: see text][Formula: see text]M, while EDTA-stabilized blood showed slightly decreased aggregation and unchanged deformation. With washed RBCs in dextran solution, the addition of sodium nitroprusside (in the concentrations of 100, and 200[Formula: see text][Formula: see text]M) resulted in decreased aggregation and increased deformation. These findings aid in our understanding of nitric oxide’s effect on RBC microrheological properties.

Условием нормальной жизнедеятельности организма является эффективный транспорт и доставка в органы и их тканевые микрорайоны кислорода и всего спектра веществ, необходимых для метаболизма. Это достигается скоординированной работой всех систем организма и в том числе крови, которая обладает уникальной текучестью и тем самым эффективно решает транспортные задачи. Интегральной реологической характеристикой крови является ее вязкость. Величина последней определяется рядом ключевых параметров, таких как вязкость плазмы, показатель гематокрита, напряжение и скорости сдвига, агрегация и деформируемость эритроцитов. Изменение этих 5 основных реологических характеристик крови и эритроцитов определяет текучесть крови и ее транспортный потенциал. В обзоре рассмотрены возможные причины и механизмы изменений указанного выше комплекса гемореологических характеристик или отдельных элементов как в норме, так и при патологии. The efficient transport and delivery of oxygen and other metabolically necessary substances to the organs and their tissue microregions is crucial for the proper functioning of the body. All body systems, including blood, cooperate. Blood has a unique fluidity that helps it transport substances effectively. Blood viscosity is an integral rheological characteristic that determines its flow properties. The value of blood viscosity is determined by several critical parameters, including plasma viscosity, hematocrit, stress and shear rates, and the aggregation and deformability of erythrocytes. The alteration of these 5 essential rheological characteristics has a significant impact on the fluidity of blood and its transport potential. The article discusses the potential causes and mechanisms responsible for altering the complex of hemorheological characteristics or individual components,both in normal and abnormal conditions.

Red blood cells (RBCs) are the most abundant human blood cells. RBC aggregation and deformation strongly determine blood viscosity which impacts hemorheology and microcirculation. In turn, RBC properties depend on different endogenous and exogenous factors. One such factor is nitric oxide (NO), which is mainly produced by endothelial cells (EC) from L-arginine amino acid in the circulatory system. Since the mechanisms of the RBC-endothelium interplay are not clear up to date and considering its possible clinical importance, the aims of this study are to investigate in vitro: (1) The effect of L-arginine induced NO on RBC aggregation and adhesion to endothelium; (2) the NO effect on RBC aggregation and deformation induced by L-arginine and sodium nitroprusside without the presence of endothelium in the samples. The RBC aggregation and adhesion to a monolayer of EC were studied using optical tweezers (OT). The RBC deformability and aggregation without endothelium in the samples were studied using the flow chamber method and Myrenne aggregometer. We confirmed that NO increases deformability and decreases aggregation of RBCs. We showed that the soluble guanylate cyclase pathway appears to be the only NO signaling pathway involved. In the samples with the endothelium, the "bell-shaped" dependence of RBC aggregation force on L-arginine concentration was observed, which improves our knowledge about the process of NO production by endothelium. Additionally, data related to L-arginine accumulation by endothelium were obtained: Necessity of the presence of extracellular L-arginine stated by other authors was put under question. In our study, NO decreased the RBC-endothelium adhesion, however, the tendency appeared to be weak and was not confirmed in another set of experiments. To our knowledge, this is the first attempt to measure the forces of RBC adhesion to endothelium monolayer with OT.

Введение. Текущая кровь из-за своей вязкости создает сопротивление потоку и тем самым оказывает влияние на величину артериального давления (АД). Это особенно важно при артериальной гипертонии (АГ), поскольку нормализация макро- и микрореологических свойств крови и эритроцитов может положительно сказаться на величине АД. Цель исследования: изучение корреляции макро- и микрореологических характеристик крови и величин АД у больных АГ. Материалы и методы. У 19 больных АГ II степени (8 женщин и 11 мужчин) и у 16 здоровых лиц (8 женщин и 8 мужчин) регистрировали параметры гемореологического профиля: вязкость крови (ВК), плазмы и суспензии эритроцитов, показатель гематокрита (Hct), отношение Hct/ВК, деформируемость (ДЭ) и агрегацию эритроцитов (АЭ). Для оценки чувствительности организма к газотрансмиттерам (ГТ) определяли микрореологические ответы эритроцитов на дозированное воздействие доноров оксида азота (NO) и сероводорода (H2S) – нитропруссида натрия (НПН) 100 мкМ и гидросульфида натрия (NaHS) 100 мкМ с последующей регистрацией ДЭ и АЭ. Результаты. У больных АГ показатели АД на 18–30% (p < 0,05) превышали нормальный уровень. При этом значения практически всех гемореологических параметров у больных существенно отличались (p < 0,05) от величин здоровых лиц. У лиц с АГ наблюдали снижение текучести крови, что сочеталось с уменьшением индекса Hct/ВК на 11% (p < 0,05). Последний параметр положительно коррелировал с ДЭ (r = 0,682; p < 0,01). Кроме того, систолическое АД корре­лировало с ДЭ (r = –0,366; p < 0,05) и с АЭ (r = 0,391; p < 0,05). С другой стороны, при инкубации эритроцитов больных АГ с НПН или с NaHS на 8–11% возрастала ДЭ, а АЭ снижалась на 42–57% (p < 0,01). У больных с относительно небольшим подъемом АД микрореологические ответы на доноры ГТ были значимо бóльшими на 35 и 60% (p = 0,03 и p < 0,05) соответственно, чем у лиц с более высоким АД. Заключение. Результаты исследования свидетельствуют о том, что величины АД у больных АГ заметно коррелируют с параметрами текучести крови и показателем ее транспортного потенциала, и что особенно важно, с ДЭ и АЭ. Introduction. Due to its viscosity the flowing blood creates resistance to the flow, thus affecting the blood pressure (BP) value. This impact is especially important in arterial hypertension (AH), since the normalization of blood macro- and microrheological properties and erythrocytes can positively affect the BP value. Aim: to study the correlation of hemorheological characteristics and BP values in patients with AH. Materials and Methods. We registered hemorheological profile parameters in 19 patients with AH stage II (8 women and 11 men) and 16 healthy individuals (8 women and 8 men). These parameters included blood viscosity (ВV), plasma and erythrocyte suspension viscosity, hematocrit (Hct) value, Hct/ВC ratio, erythrocyte deformability (ЕD) and erythrocyte aggregation (EА). To assess the body’s sensitivity to gasotransmitters (GT) we first determined erythrocyte microrheological responses to dosed exposure to donors of nitric oxide (NO) and hydrogen sulfide (H2S) – sodium nitroprusside (SPN) 100 μM and sodium hydrosulfide (NaHS) 100 μM and then registered ЕD and ЕA. Results. In AH patients, BP values were 18–30% (p < 0.05) higher than the normal level. At the same time, almost all hemorheological parameters in patients differed significantly (p < 0.05) from the values of healthy individuals. In AH patients we observed decreasing blood fluidity combined with decreasing Hct/ВC index by 11% (p < 0.05). Hct/ВC ratio positively correlated with ЕD (r = 0.682; p < 0.01). In addition, systolic BP correlated with ED (r = –0.366; p < 0.05) and EА (r = 0.391; p < 0.05). On the other hand, during the erythrocyte incubation in AH patients with SPN or NaHS, ЕD increased by 8–11%, and EА decreased by 42–57% (p < 0.01). In patients with a relatively small BP rise, microrheological responses to GT donors were significantly greater by 35% and 60% (p = 0.03 and p < 0.05), respectively, than in patients with higher BP. Conclusion. The study results indicate that BP values in AH patients significantly correlate with the parameters of blood flow and the indicator of its transport potential, and, most importantly, with ЕD and EА.

Coronary heart disease (CHD) and atrial fibrillation (AF) pose significant health risks and require accurate diagnostic tools to assess the severity and progression of the diseases. Traditional diagnostic methods have limitations in providing detailed information about blood flow characteristics, particularly in the microcirculation. This study’s objective was to examine and compare the microcirculation in both healthy volunteers and patient groups with CHD and AF. Furthermore, this study aimed to identify a relationship between blood microcirculation parameters and endothelial function. Digital capillaroscopy was employed to assess the microcirculation parameters, for example, such as capillary blood flow velocity, the size of red blood cell aggregates, and the number of aggregates per min and per running mm. The results indicate significant alterations in blood flow characteristics among patients with CHD and AF compared to healthy volunteers. For example, capillary blood flow velocity is statistically significantly decreased in the case of CHD and AF compared to the healthy volunteers (p < 0.001). Additionally, the correlation between the measured parameters is different for the studied groups of patients and healthy volunteers. These findings highlight the potential of digital capillaroscopy as a non-invasive tool for evaluating blood flow abnormalities (red blood cell aggregates and decreased capillary blood flow velocity) in cardiovascular diseases, aiding in early diagnosis and disease management.

BACKGROUND: Vascular resistance, and therefore blood pressure (BP), depends on vascular and rheological factors. Microrheological characteristics of red blood cells (RBCs) can affect blood viscosity (BV) and thus be included in the pathogenesis of increased blood pressure in arterial hypertension (AH). Signaling molecules such as gasotransmitters (NO, CO and H2S) regulate vascular tone and RBC microrheological characteristics and thus affect blood pressure and tissue perfusion. OBJECTIVE: It was evaluated the changes in the macro- and microrheological characteristics of blood and red blood cells (RBCs) under arterial hypertension in persons with and without COVID-19, as well as the protective effect of NO and H2S donors on the RBC microrheological properties. METHODS: Hemorheological profile parameters were recorded in group 1 individuals (n = 18, 9 women and 9 men) without a history of COVID-19; group 2 (n = 16; 11 females and 5 males), hypertensive patients who had COVID-19. As a control, there was a group of healthy individuals (group 3 n = 22). In experiments with red blood cells (RBCs) and their recovered ghosts (filled with an isotonic solution of known viscosity), deformability (RBCD) and aggregation (RBCA) were recorded after incubation of cells with sodium nitroprusside (SNP, 100μM) and sodium hydrosulfide (NaHS, 100μM). RESULTS: In patients with AH in both groups, the main parameters of the hemorheological profile were negatively changed, including a decrease in RBCD and an increase in BV, plasma viscosity (PV) and RBCA. SNP and NaHS significantly increased deformability and reduced their aggregation (p < 0.01). However, in healthy individuals, microrheological responses to GT donors (100μM) were more pronounced than in patients with AH, especially in the AH+COVID-19 group (p < 0.05). CONCLUSION: Both gasotransmitter donors (NO and H2S) have a positive effect on the RBC microrheological characteristics in healthy and sick individuals. However in hypertensive patients, especially those who had COVID-19, microrheological responses to GT donors were significantly lower. Therefore, on the model of red cell microrheological responses, as on a test object, it is possible to determine the decrease in the sensitivity of cells and tissues to the regulatory action of gasotransmitters.

The aim of this work was to measure parameters of platelet aggregation in patients with arterial hypertension and type 2 diabetes mellitus using light scattering technique. The degree and rate of platelets aggregation in patients with these diseases are increased compared to those in healthy people.