The Role of Red Blood Cell Membrane Rigidity on Cellular and Drug Particle Carrier Dynamics in Blood Flow

Abstract

Blood and heart-related diseases remain a significant challenge for modern-day medicine. Blood cell-related diseases have also proven to be challenging to understand and treat, specifically diseases involving the loss of deformability (rigid) in red blood cells (RBCs). Disease involving rigid RBCs are typically of genetic origin and thus limit treatment options and treatment efficacy. Rigid RBC disorders give rise to many medical complications, including vaso-occlusion, pulmonary hypertension, and cardiac dysfunction. Patients inflicted with Sickle Cell Disease (SCD), hereditary spherocytosis, iron-deficient anemia, pyruvate kinase deficiency, human immunodeficiency virus (HIV), malaria, sepsis, and even natural aging all have less deformable (rigid) RBCs than healthy patients. Rigid RBCs cause major physical damage when traveling through the body by occluding microvasculature, depriving tissues of nutrients, and damaging walls of the spleen, liver, and lungs. The core work presented in this dissertation aims to probe how decreases in RBC deformability affect hemodynamics and impact functionality of other blood cells, clarifying the pathology of RBC-related diseases. We initially present a model of artificially rigidified human RBCs which offers an experimental control over extent of membrane stiffness as well as the fractional composition of rigid RBCs in whole blood. Here, we find that the presence of rigid RBCs in blood flow significantly alters the ability of immune cells to adhere to inflammation on the vascular wall of a microfluidic model. In some cases, the presence of highly rigid RBCs reduces leukocyte adhesion to the vascular wall by up to ~80%. Following this initial investigation, we take a pivotal focus on SCD and further quantifying the whole blood characteristics of SCD pediatric patient blood and its behavior in flow. This thesis presents multiple investigations highlighting the outcome of RBC rigidity in SCD. An interesting clinical case study is highlighted in this work as well as additional in vitro work showing how the presence of RBC rigidity alters immune cell adhesion functionality. An artificial model of blood infusion therapy is also developed to test how leukocyte adhesion to inflammation is impacted upon alteration of whole blood composition. This knowledge is essential in understanding why people with diseases related to RBC deformability are susceptible to infection and have irregular immune responses. In addition, we also investigate how rigid RBCs in blood flow alter the adhesion efficacy of vascular-targeted carriers (VTCs). The field of drug delivery has taken an interest in combating numerous blood and heart diseases such as atherosclerosis via the use of VTCs. Ideally, VTC technology increases drug delivery efficacy and simultaneously reduces cytotoxic effects, precisely localizing drugs only to the disease site through receptor-ligand interactions. Cellular interactions are not yet fully understood. The dynamics of disease-inflicted cells (rigid RBCs) are even less understood, thus compounding the problem of efficient VTC design under diseased blood conditions. We investigate various particle design parameters and assess their vascular wall adhesion performance in the presence of rigid RBCs. We find the vascular adhesion of stiff microparticles is reduced by up to ~50% in the presence of rigid RBCs. Interestingly, deformable hydrogel microparticles can experience an increase in vascular adhesion of up to ~ 80%. This work explores an opportunity to develop new therapeutics with high efficacy in diseased blood.