Assessment of Fibrinogen Macromolecules Interaction with Red Blood Cells Membrane by Means of Laser Aggregometry, Flow Cytometry, and Optical Tweezers Combined with Microfluidics

in BIOMOLECULES (2020)

Effect of Red Blood Cell Aging In Vivo on Their Aggregation Properties In Vitro: Measurements with Laser Tweezers

in Applied Sciences (2020), 10(21), 7581-10

Red blood cell (RBC) aggregation highly influences hemorheology and blood microcirculation in the human body. The aggregation properties of RBCs can vary due to numerous factors, including RBC age. The ... [more ▼]

Red blood cell (RBC) aggregation highly influences hemorheology and blood microcirculation in the human body. The aggregation properties of RBCs can vary due to numerous factors, including RBC age. The aim of this work was to estimate in vitro the differences in the RBC aggregation properties of different RBC age populations in single-cell experiments using laser tweezers. RBCs from five healthy volunteers were separated into four subpopulations by Percoll density gradient centrifugation. Each subpopulation of the RBC was separately resuspended in autologous plasma or dextran 70 kDa (50 mg/mL). The aggregation force between the single cells was measured with holographic laser tweezers. The obtained data demonstrated an enhancement of RBC aggregation force in doublets with age: the older the cells, the higher the aggregation force. The obtained data revealed the differences between the aggregation and aggregability of RBC in dependence of the RBC in vivo age. [less ▲]

Macro- and Microrheological Properties of Mucus Surrogates in Comparison to Native Intestinal and Pulmonary Mucus

in BIOMACROMOLECULES (2019), 20(9), 3504-3512

Mucus is a complex hydrogel that acts as a protective barrier in various parts of the human body. Both composition and structural properties play a crucial role in maintaining barrier properties while ... [more ▼]

Mucus is a complex hydrogel that acts as a protective barrier in various parts of the human body. Both composition and structural properties play a crucial role in maintaining barrier properties while dictating diffusion of molecules and (nano)materials. In this study, we compare previously described mucus surrogates with the native human airway and pig intestinal mucus. Oscillatory shear rheology was applied to characterize mucus on the bulk macrorheological level, revealing that the artificial airway surrogate deviates from the elastic-dominant behavior of native mucus samples. We circumvented this limitation through the addition of a cross-linking polymer to the surrogate adjusting the rheological properties closer to those of native mucus. Applying particle tracking microrheology, we further demonstrated that the mechanical properties at the microscale differ significantly between artificial and native mucus. We conclude that proper characterization of mucus and its surrogates is vital for a reliable investigation of nanoparticle-based mucosal drug delivery. [less ▲]

Swimming of bacterium Bacillus subtilis with multiple bundles of flagella

in SOFT MATTER (2019), 15(48), 10029-10034

We characterize the bundle properties for three different strains of B. subtilis bacteria with various numbers of flagella. Our study reveals that, surprisingly, the number of bundles is independent of ... [more ▼]

We characterize the bundle properties for three different strains of B. subtilis bacteria with various numbers of flagella. Our study reveals that, surprisingly, the number of bundles is independent of the number of flagella, and the formation of three bundles is always the most frequent case. We assume that this relates to the fact that different mutants have the same body length. There is no significant difference between the bundle width and length for distinct strains, but the projected angle between the bundles increases with the flagellar number. Furthermore, we find that the swimming speed is anti-correlated with the projected angle between the bundles, and the wobbling angle between the swimming direction and cell body increases with the number of flagella. Our findings highlight the impact of geometrical properties of bacteria such as body length and bundle configuration on their motility. [less ▲]

Glutaraldehyde - A Subtle Tool in the Investigation of Healthy and Pathologic Red Blood Cells

in FRONTIERS IN PHYSIOLOGY (2019), 10

Glutaraldehyde is a well-known substance used in biomedical research to fix cells. Since hemolytic anemias are often associated with red blood cell shape changes deviating from the biconcave disk shape ... [more ▼]

Glutaraldehyde is a well-known substance used in biomedical research to fix cells. Since hemolytic anemias are often associated with red blood cell shape changes deviating from the biconcave disk shape, conservation of these shapes for imaging in general and 3D-imaging in particular like confocal microscopy, scanning electron microscopy or scanning probe microscopy is a common desire. Along with the fixation comes an increase in the stiffness of the cells. In the context of red blood cells this increased rigidity is often used to mimic malaria infected red blood cells because they are also stiffer than healthy red blood cells. However, the use of glutaraldehyde is associated with numerous pitfalls: (i) while the increase in rigidity by an application of increasing concentrations of glutaraldehyde is an analog process, the fixation is a rather digital event (all or none); (ii) addition of glutaraldehyde massively changes osmolality in a concentration dependent manner and hence cell shapes can be distorted; (iii) glutaraldehyde batches differ in their properties especially in the ratio of monomers and polymers (iv) handling pitfalls, like inducing shear artifacts of red blood cell shapes or cell density changes that needs to be considered, e.g., when working with cells in flow; (v) staining glutaraldehyde treated red blood cells need different approaches compared to living cells, for instance, because glutaraldehyde itself induces a strong fluorescence. Within this paper we provide documentation about the subtle use of glutaraldehyde on healthy and pathologic red blood cells and how to deal with or circumvent pitfalls. [less ▲]

Flagellar number governs bacterial spreading and transport efficiency

in SCIENCE ADVANCES (2018), 4(9),

Peritrichous bacteria synchronize and bundle their flagella to actively swim, while disruption of the bundle leads to a slow motility phase with a weak propulsion. It is still not known whether the number ... [more ▼]

Peritrichous bacteria synchronize and bundle their flagella to actively swim, while disruption of the bundle leads to a slow motility phase with a weak propulsion. It is still not known whether the number of flagella represents an evolutionary adaptation toward optimizing bacterial navigation. We study the swimming dynamics of differentially flagellated Bacillus subtilis strains in a quasi-two-dimensional system. We find that decreasing the number of flagella N-f reduces the average turning angle between two successive run phases and enhances the run time and the directional persistence of the run phase. As a result, having fewer flagella is beneficial for long-distance transport and fast spreading while having a lot of flagella is advantageous for the processes that require a slower spreading, such as biofilm formation. We develop a two-state random walk model that incorporates spontaneous switchings between the states and yields exact analytical expressions for transport properties, in remarkable agreement with experiments. The results of numerical simulations based on our two-state model suggest that the efficiency of searching and exploring the environment is optimized at intermediate values of N-f. The optimal choice of N-f, for which the search time is minimized, decreases with increasing the size of the environment in which the bacteria swim. [less ▲]

Joint Symposium Rheology-360 degrees of the Belgian Group of Rheology, German Rheological Society, and ProcessNet-Subject Division Rheology

in Applied Rheology (2018), 28(3), 53-53

Classification of red blood cell shapes in flow using outlier tolerant machine learning

in PLoS Computational Biology (2018)

Numerical–experimental observation of shape bistability of red blood cells flowing in a microchannel

in European Physical Journal E. Soft Matter (2018)

In-phase and anti-phase flagellar synchronization by waveform compliance and basal coupling

in New Journal of Physics (2017)

Cilia and flagella exhibit regular bending waves that perform mechanical work on the surrounding fluid, to propel cellular swimmers and pump fluids inside organisms. Here, we quantify a force-velocity ... [more ▼]

Cilia and flagella exhibit regular bending waves that perform mechanical work on the surrounding fluid, to propel cellular swimmers and pump fluids inside organisms. Here, we quantify a force-velocity relationship of the beating flagellum, by exposing flagellated Chlamydomonas cells to controlled microfluidic flows. A simple theory of flagellar limit-cycle oscillations, calibrated by measurements in the absence of flow, reproduces this relationship quantitatively. We derive a link between the energy efficiency of the flagellar beat and its ability to synchronize to oscillatory flows. [less ▲]