Ultrasound Standing Wave-Based Cell-to-liquid Separation for Measuring Viscosity and Aggregation of Blood Sample

Abstract

When quantifying mechanical properties of blood samples flowing in closed fluidic circuits, blood samples are collected at specific intervals. Centrifugal separation is considered as a required procedure for preparing blood samples. However, the use of centrifuge is associated with several issues, including the potential for red blood cell (RBC) lysis, clotting activation, and RBC adhesions in the tube. In this study, an ultrasonic transducer is employed to separate RBCs or diluent from blood sample. The ultrasonic radiation force is much smaller than the centrifugal force acting in centrifuge, it can avoid critical issues occurring under centrifuge. Then, the RBC aggregation and blood viscosity of the blood sample are obtained using the microfluidic technique. According to the numerical results, ultrasonic transducers exhibited a maximum quality factor at an excitation frequency of 2.1 MHz. Periodic pattern of acoustic pressure fields were visualized experimentally as a column mode. The half wavelength obtained was as 0.5 λ = 0.378 ± 0.07 mm. The experimental results agreed with the analytical estimation sufficiently. An acoustic power of 2 W was selected carefully for separating RBCs or diluent from various blood samples (i.e., Hct = 20% ~ 50%; diluent: plasma, 1x phosphate-buffered saline (PBS), and dextran solution). The present method was employed to separate fixed blood samples which tended to stack inside the tube while using the centrifuge. Fixed RBCs were collected easily with an ultrasonic transducer. After various fixed blood samples with different base solutions (i.e., glutaraldehyde solution, 1x PBS, and dextran solution) were prepared using the present method, RBC aggregation and the viscosity of the blood sample are successfully obtained. In the near future, the present method will be integrated into ex vivo or in vitro fluidic circuit for measuring multiple mechanical properties of blood samples for a certain longer period.

Sequential quantification of blood and diluent using red cell sedimentation-based separation and pressure-induced work in a microfluidic channel

“…Based on microfabrication procedures (photolithography and soft lithography) reported in our previous study, 29 a polydimethylsiloxane (PDMS) (Sylgard 184, Dow Corning, Midland, MI, USA) device was replicated from a four-inch silicon master mold. Two inlets (a and b) and one outlet were punched with a biopsy punch (outer diameter = 0.75 mm).…”

“…28 The plasma proteins in blood samples substantially enhance RBC aggregation. As RBC aggregation causes an increase in effective blood volume, 29 an increase in the gravitational force accelerates RBC sedimentation in the tube. This method quantifies the setting distance (interface movement) between RBCs and plasma, particularly after an elapsed time of 1 h. A bioelectric impedance method has been used for continuous ESR monitoring, where two needle electrodes (diameter = 0.7 mm and gap = 10 mm) are placed through the walls of a plastic tube (inner diameter = 9 mm and length = 75 mm).…”

“…This method has also been applied to quantify RBC aggregation. 30,31 More recently, periodic air-driven shear force 32 or ultrasonic acoustic pressure 29 has been suggested to accelerate the ESR in a reservoir ($5 mL) or a disposable syringe ($1 mL). During RBC sedimentation in the tube, the hematocrit varies continuously over time.…”

Quantitative Monitoring of Dynamic Blood Flows Using Coflowing Laminar Streams in a Sensorless Approach

“…The depth (h) of all channels is set to h = 20 µm. A polydimethylsiloxane (PDMS) block was replicated from a silicon master mold using microfabrication procedures, such as photolithography and soft lithography [52]. The relationship between shear stress (τ) and pressure (P) for each compartment is decoupled with a virtual wall.…”

“…This study was approved by the ethics committee of Chosun University under the reference code IRB-2-1041055-AB-N-01-2021-05. Concentrated RBCs were purchased from the Gwangju-Chonnam blood bank (Gwangju, Korea) and stored in a refrigerator at 4 • C. Whenever a specific blood sample was required to conduct experiments, normal RBCs and autologous plasma were obtained by removing the buffy layer and debris using the washing procedures reported in our previous study [52]. Subsequently, suspended blood was prepared by adding normal RBCs to a specific diluent (i.e., 1× PBS, plasma, glycerin solution, and dextran solution).…”