Flow Behavior Of Erythrocytes Research Articles

Microfluidic-based laser speckle contrast imaging of erythrocyte flow and magnetic nanoparticle retention in blood

The present study aims to develop a microfluidic system in combination with laser speckle contrast imaging (LSCI) for the study of erythrocyte dynamics under various physiological flow conditions. Microfluidic device was fabricated and red blood cell suspension was introduced at various flow rate controlled by a syringe pump. Relative blood velocity profile in the microfluidic chamber was obtained by LSCI in a real-time manner and correlated well with simulated results by computational fluid dynamics. A close correlation of relative blood velocity, inlet flow rate and blood viscosity were found using this microfluidic-based LSCI system. In addition, our platform also allows the demonstration of spatiotemporal variation of blood flow in response to magnet-induced magnetic nanoparticle (MNP) retention. The flow behaviour of erythrocytes with the presence of MNPs appeared to be closely correlated with the location of the magnet placement. Our microfluidic-based LSCI measurement represents a simple yet controllable experimental model for evaluating the variations in different hemorheological conditions in vitro and has a strong potential as an easy-to-use tool for investigating local MNP retention and hemodynamic changes.

A203 Blood Cell Motions and Interactions in Microchannels

Detailed knowledge on the motions and interactions of individual blood cells flowing in microchannels is essential to provide a better understanding on the blood rheological properties and disorders in microvessels. This paper presents the ability of a confocal micro-PTV system to track red blood cells (RBCs) through a 100 μm circular glass microchannel. The technique consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) software (MtrackJ). Detailed measurements on the motions of RBCs were measured at different haematocrits (Hct). Our results show clearly that this technique can provide detailed information about microscale disturbance effects caused by the blood cells.1) Goldsmith, H.: Red cell motions and wall interactions in tube flow, Federation Proceedings, Vol. 30, No.5 (1971) pp. 1578-1588.2) Goldsmith, H. and Marlow J.: Flow behavior of erythrocytes. 11. Particles motions in concentrated suspensions of ghost cells, Journal of Colloid and Interface Science, Vol. 71, No. 2 (1979) pp. 383-407.3) Lima, R., et al.: Confocal micro-PIV measurements of three dimensional profiles of cell suspension flow in a square microchannel, Meas. Sci. Tech., Vol. 17, (2006) pp. 797-808.4) Lima, R., et al., In vitro confocal micro-PIV measurements of blood flow in a square microchannel: the effect of the haematocrit on instantaneous velocity profiles, J. Biomech., (in press).5) Abramoff, M., et al.: Image processing with lmageJ, Biophotonics International, Vol. 11, No. 7 (2004) pp. 36-42.6) Meijering, E., et al.: Tracking in Molecular Bioimaging, , IEEE Signal Processing Magazine, Vol 23. No. 3 (2006) pp. 46-53.

A multi-component lattice Boltzmann scheme: Towards the mesoscale simulation of blood flow

While blood at the macroscopic scale is frequently treated as a continuum by techniques such as computational fluid dynamics, its mesoscale behaviour is not so well investigated or understood. At this scale, the deformability of each cell within the plasma is important and cannot be ignored. However there is currently a lack of efficient computational techniques able to simulate a large number of deformable particles such as blood cells. This paper addresses this problem and demonstrates the applicability of the authors’ recent multi-component lattice Boltzmann method for the simulation of a large number of mutually immiscible liquid species [Dupin MM, Halliday I, Care CM. Multi-component lattice boltzmann equation for mesoscale blood flow. J Phys A: Math Gen 2003;36:8517–34]. In here, biological cells are treated as immiscible, deformable, and relatively viscous drops (compared to the surrounding fluid). The validation of the model is based on the work of Goldsmith on the flow of solid particles, deformable particles and red blood cells [Goldsmith HL, Marlow JC. Flow behavior of erythrocytes. II. Particle motions in concentrated suspensions of ghost cells. J Colloid Interf Sci 1979;71:383–407]. We demonstrate, in particular, that the model recovers Goldsmith’s observations on the flow properties of red blood cells and also the experimental observations of Frank on the flow of solid beads [Frank M, Anderson D, Weeks ER, Morris JF. Particle migration in pressure-driven flow of a brownian suspension. J Fluid Mech 2003;493:363–78]. The current article is the first validation of our new lattice Boltzmann model for a large number of deformable particles in this context and demonstrates that the method provides a new, and effective, approach for the modeling of mesoscale blood flow.

Imaging of oxygen saturation and distribution of erythrocytes in microvessels.

To construct images of oxygen saturation and the distribution of erythrocytes in a network of microvessels. The image of a small group of microvessels under an inverted microscope was incorporated into an image processor through a video camera and was digitized. Based on the information obtained through six visible interference filters of different wavelengths, oxygen saturation and the amount of erythrocytes in microvessels were calculated with a computer. The system was applied to a microvascular bed of isolated rabbit mesentery perfused with a suspension of human erythrocytes. In a steady flow, with lowering of tissue oxygen tension by superfusion with nitrogen-bubbled isotonic saline containing 20 mmol/L sodium dithionite, the decrease of oxygen saturation of erythrocytes from arterioles to venules was imaged. Simultaneously, the distribution of erythrocytes in the microvessels was imaged and the marginal cell-free layer was profiled under high magnification. No significant alteration of the erythrocyte distribution on the deoxygenation of erythrocytes was observed. The exposure of erythrocytes to acidic pH and the decrease of the flow velocity of erythrocytes increased the release of oxygen from the erythrocytes in microvessels. The present method will be useful for the comprehensive analysis of oxygen transfer in the microvascular network, on the basis of both changes of the oxygen saturation and the flow behavior of erythrocytes.

Difference of the flow behavior of erythrocytes in microvessels and glass

Difference of the flow behavior of erythrocytes in microvessels and glass

Changes of flow behavior of erythrocytes in microvessels and flow

Changes of flow behavior of erythrocytes in microvessels and flow

Flow behavior of erythrocytes. II. Particle motions in concentrated suspensions of ghost cells

The detailed motions of individual human red blood cells (rbc) were studied under the microscope in transparent suspensions of red cell ghosts (serving as a model for whole blood) by tracking the particles in flow through tubes having radii R 0 of 32 to 80 μm at Reynolds numbers from 10 −3 to 0.3, and volume concentrations c from 0.10 to 0.93. The rbc velocity distributions were blunted from the parabolic at c > 0.2 with a region of plug flow of radius R c in the core of the tube where the velocities u M were measurably constant. R c increased with increasing c, and decreased with increasing flow rate Q and R 0. At c > 0.4, the rbc were continuously deformed from the resting biconcave shape, and their major axes became aligned within 20° of the flow. By contrast, gluteraldehyde-hardened red cells (hbc) continued to rotate with varying angular velocities, even at c = 0.93. The paths of the rbc exhibited erratic radial displacements whose magnitude and frequency at a given c increased with increasing shear rate, and in a given tube was greatest at 0.2 < c < 0.4 and with particles at radial positions 0.4 < R/ R 0 < 0.8. Appreciable radial displacements also occurred in the plug flow region where it was shown that shear rates of the order 0.01 u M/ R c existed. The distributions of rbc across the median plane of the tube were also measured. At high Q and c < 0.43 there was a pronounced movement of rbc to the periphery, perhaps due to differences in the rates of radial migration between rbc and ghosts stemming from differences in their densities.

Flow behaviour of erythrocytes - I. Rotation and deformation in dilute suspensions

The behaviour of individual human red cells and rouleaux were studied under the micro­scope in suspensions of &lt; 2% haematocrit: (i) in Poiseuille flow by tracking the particles in glass tubes, and (ii) in Couette flow by observing cells in the stationary layer between counter-rotating glass disks. At shear stresses ≪ 0.1 N m -2 , the rotations of red cells in plasma were in accord with theory applicable to rigid disks. At shear stresses &gt; 0.1 N m -2 , especially in viscous isotonic Dextran solutions, the cells oriented themselves at a constant angle to the flow and their membrane appeared to rotate about the interior. Although this behaviour was analogous to that of liquid drops, the concavity was still present in the de­formed erythrocytes, whose mean major diameters in plasma increased by 1.05 µm as the shear stress increased from 0 to 0.4 N m -2 . Deformation, through bending, was also observed with linear rouleaux of &gt; 6 cells, here, at even the lowest shear stresses. By contrast, glutaraldehyde hardened cells and rouleaux rotated, without deforming, as rigid disks and rods respectively.