Novaflux Inc., Princeton, NJ 08540, USA.
Advanced BioDevices LLC, Princeton, NJ 08540, USA.
Soft Matter. 2022 Jan 19;18(3):554-565. doi: 10.1039/d1sm01299a.
Sickle cell anemia (SCA) is a disease that affects red blood cells (RBCs). Healthy RBCs are highly deformable objects that under flow can penetrate blood capillaries smaller than their typical size. In SCA there is an impaired deformability of some cells, which are much stiffer and with a different shape than healthy cells, and thereby affect regular blood flow. It is known that blood from patients with SCA has a higher viscosity than normal blood. However, it is unclear how the rigidity of cells is related to the viscosity of blood, in part because SCA patients are often treated with transfusions of variable amounts of normal RBCs and only a fraction of cells will be stiff. Here, we report systematic experimental measurements of the viscosity of a suspension varying the fraction of rigid particles within a suspension of healthy cells. We also perform systematic numerical simulations of a similar mixed suspension of soft RBCs, rigid particles, and their hydrodynamic interactions. Our results show that there is a rheological signature within blood viscosity to clearly identify the fraction of rigidified cells among healthy deformable cells down to a 5% volume fraction of rigidified cells. Although aggregation of RBCs is known to affect blood rheology at low shear rates, and our simulations mimic this effect an adhesion potential, we show that such adhesion, or aggregation, is unlikely to provide a physical rationalization for the viscosity increase observed in the experiments at moderate shear rates due to rigidified cells. Through numerical simulations, we also highlight that most of the viscosity increase of the suspension is due to the rigidity of the particles rather than their sickled or spherical shape. Our results are relevant to better characterize SCA, provide useful insights relevant to rheological consequences of blood transfusions, and, more generally, extend to the rheology of mixed suspensions having particles with different rigidities, as well as offering possibilities for developments in the field of soft material composites.
镰状细胞贫血症 (SCA) 是一种影响红细胞 (RBC) 的疾病。健康的 RBC 具有高度的变形能力，在流动时可以穿透比其典型尺寸小的毛细血管。在 SCA 中，一些细胞的变形能力受损，这些细胞比健康细胞更硬，形状也不同，从而影响正常的血流。众所周知，SCA 患者的血液比正常血液具有更高的粘度。然而，细胞的刚性与血液的粘度之间的关系尚不清楚，部分原因是 SCA 患者经常接受不同数量的正常 RBC 输血，只有一部分细胞会变硬。在这里，我们报告了系统实验测量的健康细胞悬浮液中刚性粒子分数变化时悬浮液粘度的变化。我们还对类似的软 RBC、刚性粒子及其水动力相互作用的混合悬浮液进行了系统的数值模拟。我们的结果表明，在血液粘度中存在流变学特征，可以清楚地识别出健康可变形细胞中刚性化细胞的分数，直到刚性化细胞的体积分数达到 5%。尽管众所周知 RBC 聚集会在低剪切速率下影响血液流变性，并且我们的模拟模拟了这种效应——粘附势，但我们表明，由于刚性化细胞，这种粘附或聚集不太可能为在中等剪切速率下观察到的实验中观察到的粘度增加提供物理合理化。通过数值模拟，我们还强调了悬浮液粘度的大部分增加是由于粒子的刚性，而不是它们的镰状或球形形状。我们的结果与更好地表征 SCA 有关，为血液输血的流变性后果提供有用的见解，更一般地说，扩展到具有不同刚性粒子的混合悬浮液的流变性，以及为软材料复合材料领域的发展提供可能性。
