Abstract
Red blood cell (RBC) aggregation causes to alter hemodynamic behaviors at low flow-rate regions of post-capillary venules. Additionally, it is significantly elevated in inflammatory or pathophysiological conditions. In this study, multiple and periodic measurements of RBC aggregation and erythrocyte sedimentation rate (ESR) are suggested by sucking blood from a pipette tip into parallel microfluidic channels, and quantifying image intensity, especially through single experiment. Here, a microfluidic device was prepared from a master mold using the xurography technique rather than micro-electro-mechanical-system fabrication techniques. In order to consider variations of RBC aggregation in microfluidic channels due to continuous ESR in the conical pipette tip, two indices (aggregation index (AI) and erythrocyte-sedimentation-rate aggregation index (EAI)) are evaluated by using temporal variations of microscopic, image-based intensity. The proposed method is employed to evaluate the effect of hematocrit and dextran solution on RBC aggregation under continuous ESR in the conical pipette tip. As a result, EAI displays a significantly linear relationship with modified conventional ESR measurement obtained by quantifying time constants. In addition, EAI varies linearly within a specific concentration of dextran solution. In conclusion, the proposed method is able to measure RBC aggregation under continuous ESR in the conical pipette tip. Furthermore, the method provides multiple data of RBC aggregation and ESR through a single experiment. A future study will involve employing the proposed method to evaluate biophysical properties of blood samples collected from cardiovascular diseases.
Highlights
Normal red blood cell (RBC) in autologous plasma suspension tends to aggregate and form rouleaux under extremely low shear-rate conditions [1,2]
After blood flow in a microfluidic channel is agitated with external sources such as pressure source [13], syringe pump [2,14], and pinch valve [3], RBC aggregation is immediately quantified by constructing variations of image intensity [3,13,14,15], laser back-scattering [16], ultrasound signal [17], or electrical impedance [18] with an elapse of time
Since RBCs aggregation was quantified at stationary blood flows by clamping polyethylene tube with a pinch valve, blood flow in each channel does not have an influence on measurement of RBCs aggregation
Summary
Normal red blood cell (RBC) in autologous plasma suspension tends to aggregate and form rouleaux (i.e., stacks-of-coins) under extremely low shear-rate conditions [1,2]. Hematocrit of blood supplied into a microfluidic channel decreases over time due to continuous ESR in the disposable syringe This variation in hematocrit is used to measure ESR by quantifying image intensity of blood within a region-of-interest (ROI) of a microfluidic channel [15]. The method is devised to monitor RBC-depleted region in a disposable syringe It does not provide sufficient information on RBC aggregation of blood in a microfluidic channel. RBC aggregation should be quantified as mean ± standard deviation in single experiment with respect to an elapse of time It does not require repetitive tests, which cause rheological properties to vary continuously
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