Continuous force-displacement relationships for the human red blood cell at different erythrocytic developmental stages of Plasmodium falciparum malaria parasite

Prior work involving either aspiration of infected cells into micropipette under suction pressure or deformation in laminar shear flow revealed that the malaria parasite Plasmodium (P.) falciparum could result in significant stiffening of infected human red blood cells (RBCs). In this paper, we present optical tweezers studies of progressive changes to nonlinear mechanical response of infected RBCs at different developmental stages of P. falciparum. From early ring stage to late trophozoite and schizont stages, up to an order of magnitude increase in shear modulus was found under controlled mechanical loading by combining experiments with threedimensional computational simulations. These results provide novel approaches to study changes in mechanical deformability in the advanced stages of parasite development in the erythrocyte, and suggest a significantly greater stiffening of the red blood cell due to P. falciparum invasion than that considered from previous studies.