A checker for evaluating red blood cell (RBC) deformability at the highest level developed
Will be useful for evaluating the risk of cardiac and cerebral infarcts
A red blood cell (RBC) deformability measurement method using a microfluidic channel had the advantage of high throughput, but the reliability of data obtained through the method was not guaranteed, so it was far from practical use. The correlation coefficient between cell velocities (index for evaluating deformability) and cell deformability in a microfluidic chip ranged from 0.3 to 0.8. Therefore, the reliability of RBC deformability measurements was in question because of such low correlation coefficients between obtained cell velocity in microfluidic channels and cell deformability.
A group of researchers led by Professor KANEKO Makoto (Graduate School of Engineering) and Professor SAKATA Yasushi (Graduate School of Medicine) at Osaka University developed an RBC deformability checker containing a microfluidic channel boasting the world’s highest-level correlation value, showing a significant difference of RBC deformability between patients with peripheral vascular disease and normal subjects.
Implementing a fundamental review of the design of channels in the microfluidic chip for evaluating cell stiffness-based deformability, based on a new idea of fluid engineering, this group succeeded in obtaining the world’s highest value at 0.92 on average (the highest correlation value: 1.0), as the correlation coefficient between obtained cell velocity in microfluidic channel and cell deformability, assuring the reliability of experimental data. Using the chip they developed, this group found that there were statistical differences in the RBC deformability index between patients with cardiovascular diseases and healthy individuals.
This group’s achievement will make the introduction of a new biomarker of the RBC deformability index in evaluating the risk of cardiovascular diseases more realistic. In addition, it will also lead to the clarification of new disease conditions and the development of therapeutic methods targeting RBC deformability.
Abstract
An on-chip deformability checker is proposed to improve the velocity–deformation correlation for red blood cell (RBC) evaluation. RBC deformability has been found related to human diseases, and can be evaluated based on RBC velocity through a microfluidic constriction as in conventional approaches. The correlation between transit velocity and amount of deformation provides statistical information of RBC deformability. However, such correlations are usually only moderate, or even weak, in practical evaluations due to limited range of RBC deformation. To solve this issue, we implemented three constrictions of different width in the proposed checker, so that three different deformation regions can be applied to RBCs. By considering cell responses from the three regions as a whole, we practically extend the range of cell deformation in the evaluation, and could resolve the issue about the limited range of RBC deformation. RBCs from five volunteer subjects were tested using the proposed checker. The results show that the correlation between cell deformation and transit velocity is significantly improved by the proposed deformability checker. The absolute values of the correlation coefficients are increased from an average of 0.54 to 0.92. The effects of cell size, shape and orientation to the evaluation are discussed according to the experimental results. The proposed checker is expected to be useful for RBC evaluation in medical practices.
Figure 1. The driving pressure for the flow inside the microfluidic chip is regulated by the pressure sensor and the syringe pump. The velocity and size of red blood cells through microchannels are measured by the high-speed camera.
Figure 2. Three different width constrictions are fabricated inside the microfluidic chip. The deformability of each red blood cell is evaluated by its velocity and deformation through a constriction.
To learn more about this research, please view the full research report entitled “ An On-Chip RBC Deformability Checker Significantly Improves Velocity-Deformation Correlation ” at this page of the Micromachines website.
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