Red Blood Cells from Individuals with Abdominal Obesity or Metabolic Abnormalities Exhibit Less Deformability upon Entering a Constriction

2020

Micromachines

To quantify the variation of red blood cells (RBCs) or plasma proteins in blood samples effectively, it is necessary to measure blood viscosity and erythrocyte sedimentation rate (ESR) simultaneously. Conventional microfluidic measurement methods require two syringe pumps to control flow rates of both fluids. In this study, instead of two syringe pumps, two air-compressed syringes (ACSs) are newly adopted for delivering blood samples and reference fluid into a T-shaped microfluidic channel. Under fluid delivery with two ACS, the flow rate of each fluid is not specified over time. To obtain velocity fields of reference fluid consistently, RBCs suspended in 40% glycerin solution (hematocrit = 7%) as the reference fluid is newly selected for avoiding RBCs sedimentation in ACS. A calibration curve is obtained by evaluating the relationship between averaged velocity obtained with micro-particle image velocimetry (μPIV) and flow rate of a syringe pump with respect to blood samples and reference fluid. By installing the ACSs horizontally, ESR is obtained by monitoring the image intensity of the blood sample. The averaged velocities of the blood sample and reference fluid (<UB>, <UR>) and the interfacial location in both fluids (αB) are obtained with μPIV and digital image processing, respectively. Blood viscosity is then measured by using a parallel co-flowing method with a correction factor. The ESR is quantified as two indices (tESR, IESR) from image intensity of blood sample (<IB>) over time. As a demonstration, the proposed method is employed to quantify contributions of hematocrit (Hct = 30%, 40%, and 50%), base solution (1× phosphate-buffered saline [PBS], plasma, and dextran solution), and hardened RBCs to blood viscosity and ESR, respectively. Experimental Results of the present method were comparable with those of the previous method. In conclusion, the proposed method has the ability to measure blood viscosity and ESR consistently, under fluid delivery of two ACSs.

Section: Introductionmentioning

confidence: 99%

Microfluidic-Based Biosensor for Blood Viscosity and Erythrocyte Sedimentation Rate Using Disposable Fluid Delivery System

2020

Micromachines

“…Because the number of RBCs (red blood cells) is significantly higher than the other cells (platelet, white blood cell), hemorheological properties of blood are dominantly determined by those of the RBCs [5,6]. Hemorheological properties including haematocrit [7,8,9,10], blood viscosity [11,12,13,14], RBC aggregation [15,16,17,18,19,20,21,22], and RBC deformability [14,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38] have been proposed for the early detection of CVDs [39,40]. RBC aggregation leads to altering the hemorheological property, especially in lower blood flows of post-capillary venules [5,41].…”

Section: Introductionmentioning

confidence: 99%

Microfluidic-Based Biosensor for Sequential Measurement of Blood Pressure and RBC Aggregation Over Continuously Varying Blood Flows

2019

Micromachines

Aggregation of red blood cells (RBCs) varies substantially depending on changes of several factors such as hematocrit, membrane deformability, and plasma proteins. Among these factors, hematocrit has a strong influence on the aggregation of RBCs. Thus, while measuring RBCs aggregation, it is necessary to monitor hematocrit or, additionally, the effect of hematocrit (i.e., blood viscosity or pressure). In this study, the sequential measurement method of pressure and RBC aggregation is proposed by quantifying blood flow (i.e., velocity and image intensity) through a microfluidic device, in which an air-compressed syringe (ACS) is used to control the sample injection. The microfluidic device used is composed of two channels (pressure channel (PC), and blood channel (BC)), an inlet, and an outlet. A single ACS (i.e., air suction = 0.4 mL, blood suction = 0.4 mL, and air compression = 0.3 mL) is employed to supply blood into the microfluidic channel. At an initial time (t < 10 s), the pressure index (PI) is evaluated by analyzing the intensity of microscopy images of blood samples collected inside PC. During blood delivery with ACS, shear rates of blood flows vary continuously over time. After a certain amount of time has elapsed (t > 30 s), two RBC aggregation indices (i.e., SEAI: without information on shear rate, and erythrocyte aggregation index (EAI): with information on shear rate) are quantified by analyzing the image intensity and velocity field of blood flow in BC. According to experimental results, PI depends significantly on the characteristics of the blood samples (i.e., hematocrit or base solutions) and can be used effectively as an alternative to blood viscosity. In addition, SEAI and EAI also depend significantly on the degree of RBC aggregation. In conclusion, on the basis of three indices (two RBC aggregation indices and pressure index), the proposed method is capable of measuring RBCs aggregation consistently using a microfluidic device.

“…The biophysical properties of blood, such as shearing viscosity, viscoelasticity, RBC aggregation, and RBC deformability, [1][2][3] could provide valuable information on the variations in hematological disorders or diseases. [4][5][6][7][8] Among them, RBC deformability plays an essential role in gas transport and flow regulation. 9 In other words, owing to its high flexibility, individual RBC can pass through extremely narrow-sized capillary or endothelial slits in the spleen.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous measurement of erythrocyte deformability and blood viscoelasticity using micropillars and co-flowing streams under pulsatile blood flows

2017

Biomicrofluidics

The biophysical properties of blood provide useful information on the variation in hematological disorders or diseases. In this study, a simultaneous measurement method of RBC (Red Blood Cell) deformability and blood viscoelasticity is proposed by evaluating hemodynamic variations through micropillars and coflowing streams under sinusoidal blood flow. A disposable microfluidic device is composed of two inlets and two outlets, two upper side channels, and two lower side channels connected to one bridge channel. First, to measure the RBC deformability, the left-lower side channel has a deformability assessment chamber (DAC) with narrow-sized micropillars. Second, to evaluate the blood viscoelasticity in co-flowing streams, a phosphate buffered saline solution is supplied at a constant flow rate. By closing or opening a pinch valve connected to the outlet of DAC, blood flows in forward or back-and-forth mode. A time-resolved micro-particle image velocimetry technique and a digital image processing technique are used to quantify the blood velocity and image intensity. Then, RBC deformability is evaluated by quantifying the blood volume passing through the DAC under forward flow, and quantifying the variations of blood velocity and image intensity in the DAC under back-and-forth flow. Using a discrete circuit model, blood viscoelasticity is obtained by evaluating variations of blood velocity and co-flowing streams. The effect of several factors (period, hematocrit, and base solution) on the performance is quantitatively evaluated. Based on the experimental results, the period of sinusoidal flow and hematocrit are fixed at 30 s and 50%, respectively. As a performance demonstration, the proposed method is employed to detect the homogeneous and heterogeneous blood composed of normal RBCs and hardened RBCs. These experimental results show that the RBC deformability is more effective to detect minor subpopulations of heterogeneous bloods, compared with blood viscoelasticity. Therefore, it leads to the conclusion that the proposed method has the ability to evaluate RBC deformability and blood viscoelasticity under sinusoidal blood flow, with sufficient accuracy and highthroughput. Published by AIP Publishing. [http://dx