Abstract
Sickle cell disorder (SCD) is a multisystem disease with heterogeneous phenotypes. Al-
though all patients have the mutated hemoglobin (Hb) in the SS phenotype, the severity and frequency
of complications are variable. When exposed to low oxygen tension, the Hb molecule becomes dense
and forms tactoids, which lead to the peculiar sickled shapes of the affected red blood cells, giving
the disorder its name. This sickle cell morphology is responsible for the profound and widespread
pathologies associated with this disorder, such as vaso-occlusive crisis (VOC). How much of the
clinical manifestation is due to sickled erythrocytes and what is due to the relative contributions of
other elements in the blood, especially in the microcapillary circulation, is usually not visualized and
quantified for each patient during clinical management. Here, we used a microfluidic microcirculation
mimetic (MMM), which has 187 capillary-like constrictions, to impose deformations on erythrocytes
of 25 SCD patients, visualizing and characterizing the morpho-rheological properties of the cells in
normoxic, hypoxic (using sodium meta-bisulfite) and treatment conditions (using hydroxyurea). The
MMM enabled a patient-specific quantification of shape descriptors (circularity and roundness) and
transit time through the capillary constrictions, which are readouts for morpho-rheological proper-
ties implicated in VOC. Transit times varied significantly (p < 0.001) between patients. Our results
demonstrate the feasibility of microfluidics-based monitoring of individual patients for personalized
care in the context of SCD complications such as VOC, even in resource-constrained settings
