RBC deformability fractionation and hydrodynamic trapping for studying Plasmodium Falciparum infection

Abstract: There have been several studies which indicate a preferential invasion towards younger red blood cells (RBCs) for the malarial parasite, P. Falciparum. Knowledge about a preferential mechanism could aid in the development of novel anti-malarial drugs. While the preference in these reports has been studied with density-separation of red blood cells, separating the cells by deformability may be a more accurate method of isolating groups of RBCs with differing age. This thesis has investigated the details of separating RBCs by deformability in the microuidic technique Deterministic Lateral Displacement (DLD). RBCs have been observed to undergo strong deformation in the device but the large size variation of RBCs together with RBC shape transformations inside the shallow channels have interfered with the separation by deformability. Further studies where higher device driving pressures with alternative device designs are utilized and the deformability of the separated cells are benchmarked towards existing techniques are proposed. Furthermore, on-chip invasion of trapped RBCs has been investigated using hydrodynamic trapping arrays. The trapping arrays allow for convenient and highly-controllable investigation of the invasion dynamics. The trapping arrays have been fabricated using replica molding and been used to successfully immobilize RBCs. Trap occupancy rates up to 85% over the span of 14 min have been achieved. On-chip parasitic behavior has been investigated. It involved several complications including the prevention of late-stage parasite rupture due to shape transformation of RBCs into echinocytic (crenated cells) when introduced into shallow PDMS (polydimethylsiloxane) channels. This complication seem to affect the rupturing of late-stage infected RBCs inside the channels. Alternative materials and surface-coating should be explored to minimize any channel-derived artefacts.