RBC deformability measurement based on variations of pressure in multiple micropillar channels during blood delivery using a disposable air-compressed pump

Abstract

Subpopulations of red blood cells (RBCs) are attributed to symptoms associated with hematological disorders. To detect differences in subpopulations of RBCs, RBC deformability has been considered as a promising label-free biomarker. To realize high throughput and a label-free approach, previous methods have required bulky syringe pumps for blood delivery and time-resolved micro-PIV techniques to obtain blood velocity fields. In this study, blood (∼0.2 mL) is delivered using a disposable air-compressed pump. Subsequently, RBC deformability is quantified by analyzing the cell-to-liquid interface in the pressure channel (β) caused by successive clogging of RBCs in multiple micropillar channels. By averaging temporal variations in the intensity of captured images of the blood within the pressure channel for a specific duration, a normalized deformability index (DI_β) is defined to quantify RBC deformability. Through the operation of the disposable air-compressed pump, blood velocity is gradually reduced over time. As observed, RBC clogging in the micropillar channel led to an increase in the value of β accompanied by fluctuations with the passage of time. A quantitative comparison of the proposed method (DI_β) against the previous method (ΔV) is performed using blood samples composed of homogeneous and heterogeneous hardened RBCs. Upon performing linear regression analysis between DI_β and ΔV, the coefficient of regression provides values as high as R² = 0.96–0.99 (i.e., P < 0.001). Thus, DI_β could be effectively used to detect variations in the deformability of RBCs. Finally, the variation in RBC deformability is quantified over a storage period of 1 week. As a result, the values of these properties remained constant for a storage time of 1 week. The indices exhibited a significant relationship because regression analysis yielded a high value of R² = 0.7916 (i.e., P < 0.001). In view of these experimental demonstrations, the proposed method of the normalized deformability index can be used to quantify RBC deformability, especially using a disposable air-compressed pump.