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UBC Theses and Dissertations

Red blood cell trans-dispersion revealing biophysical signatures in malaria parasitism Santoso, Aline Teresa


Red blood cell (RBC) deformability plays an important role in the pathogenesis of Plasmodium falciparum malaria, and therefore could potentially enable simple, rapid, and reagent-free biophysical assays. A key challenge, however, is that pathological cells often only represent a small fraction of the sample, which requires testing a large number of individual cells to enable their detection. Additionally, it is often desirable to perform multiple assays simultaneously, which require technologies capable of parallelized analysis. Traditional technologies for analyzing RBC deformability are limited by their experimental difficulty, extensive instrumentation requirements, as well as their lack of throughput and parallelizability. Here, a new microfluidic mechanism called trans-dispersion is developed to address these issues, enabling a high-throughput and parallelized analysis of RBC deformability. The trans-dispersion mechanism transports single RBCs through a series of constrictions in a microfluidic channel, where their transit speed is a function of their deformability. This process is analogous to gel-electrophoresis, where the migration speed of molecules depends on their length. To ensure a sensitive and consistent measurement, the geometry of the constriction is sized such that the transiting cell forms a temporary seal with each constriction while supporting microchannels ensure consistent forces are applied to each deformation channel. After undergoing repeated deformations, the final position of each RBC, indicating its deformability, is determined using simple bright-field microscopy and automated image processing, and thereby resulting in a repeatable, high-throughput and parallelized process. The performance of this mechanism was evaluated by detecting changes in RBC deformability resulting from chemical degradation, malaria parasitism and exposure to anti-malarial drugs. This device can distinguish variation in RBC deformability following chemical degradation using small concentrations (0.0005%) of glutaraldehyde (GTA). P. falciparum-infected RBCs (iRBCs) show distinct deformability curves compared to the uninfected controls. The linear correlation between the parasitemia and the percentage of non-transiting cells could potentially be used to infer the parasitemia of clinical specimen. Furthermore, this device was able to simultaneously assess the efficacy of several antimalarial compounds; showing that rigidification of P. falciparum-iRBCs can potentially be used to evaluate antimalarial drug efficacy, as well as serve as a functional screen for new antimalarials.

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