Applying a microfluidic 'deformability cytometry' to measure stiffness of malaria-infected red blood cells at body and febrile temperatures

Abstract

Red blood cells (RBCs) undergo repeated deformation as they traverse blood vessel, capillaries and splenic cords; RBC deformability is therefore crucial in maintaining normal blood circulation. During falciparum malaria, parasite proteins interact with the spectrin network of host RBCs, moderately stiffening the ring stage infected cells (rings). The subtle modification in the deformability of rings is however believed to be significant enough to trigger their retention by human spleen. In addition, recent studies demonstrated considerable stiffening of parasitized RBCs at febrile temperature, highlighting the temperature-dependent physiological consequences in microcirculation. A quantitative characterization of the dynamic process of RBC deformation at physiologically relevant temperatures is therefore highly desirable. In this work, a microfluidic device with bottleneck arrays is developed to mimic RBCs' travelling through narrow in-vivo constrictions such as splenic cordal meshwork and blood capillaries. For the first time, we report the dynamic mechanical responses of rings in a large population of co-cultured uninfected cells at both body and febrile temperatures. Experiments revealed that the deformability cytometer can differentiate parasitized RBCs from normal RBCs most efficiently at febrile temperature, suggesting a potential role of fever in facilitating splenic clearance. Similar dynamic deformability measurements were also conducted on RBCs with anti-malarial drug treatment; the drug effect on the deformability of both normal and parasitized cells is assessed.