Characterization of shear stress preventing red blood cells aggregation at the individual cell level: The temperature dependence

BACKGROUND: The novel measure of the red blood cells (RBC) aggregation (RBC-A) - the critical (minimum) shear stress (CSS) to prevent the cells from aggregation was found to be a promising clinically significant parameter. However, the absolute values of this parameter were found to change significantly depending on the shearing geometry (cup-and-bob, cone-plate or microchannel-flow) and have different temperature dependences along with it. The direct confirmation of these dependences aimed to find out the correct values is still pending. OBJECTIVE: In this work, we aim to assess the absolute values of CSS at different temperatures. METHODS: The single cell level measurements of CSS were performed using optical tweezers. The measurements were carried out in heavily diluted suspensions of RBCs in plasma. RESULTS: The temperature dependent changes in CSS were measured at the points (22 and 38°C), in which the cup-and-bob and cone-plate systems yielded about 1.5-fold different values, while the microchannel-flow system yielded a constant value. The single cell CSS were found to be 362±157mPa (22°C) and 312±57mPa (38°C). CONCLUSIONS: Our results prove that the microfluidic-flow approach is reflecting the RBC-A correctly. While the CSS values measured with other systems show the temperature dependent effect of the shearing geometry.