Engineering Particle-based Therapies to Modulate Neutrophil Migration in Acute Inflammation

Abstract

Acute inflammation is a critical component of the immune response to harmful stimuli such as invading pathogens or tissue injury. Neutrophils, the first white blood cells recruited to sites of infection or trauma, promptly migrate from the bloodstream to the inflamed tissue. As first responders, neutrophils play a vital role in removing the initial insult and starting the resolution phase of inflammation. The timely and coordinated action of neutrophils during inflammation is essential for maintaining homeostasis and host defense. However, prolonged neutrophil activity, characterized by uncontrolled and excessive recruitment to inflamed sites, causes tissue damage and exacerbates the progression of acute inflammatory disorders such as acute respiratory distress syndrome (ARDS), thrombosis, and sepsis. Therefore, regulating neutrophil function offers a promising therapeutic strategy for attenuating tissue damage caused by neutrophils in acute inflammatory disorders. Particle-based treatments for inflammatory diseases have gained attention due to the ability to tune particulate carrier properties such as size, shape, surface chemistry, and deformability. Specifically, particle therapies have been used to regulate immune cell infiltration at inflammation sites, including neutrophils. Therefore, the overarching goal of this dissertation is to investigate the design rationale of particle systems, focusing on surface modifications and shape to optimize neutrophil modulation in acute inflammation. In this work, we utilized cargo-free, biodegradable, and anti-inflammatory salicylic acid-based (Poly-SA) polymeric particles as the model carrier for our investigation. (1) We developed vascular-targeted Poly-SA particles and confirmed their ability to bind to pathological areas both in vitro and in vivo. We utilized various techniques, including fluorescent microscopy and ex vivo tissue analysis, to verify the binding and accumulation of Poly- SA in inflamed vascular regions. Next, (2) we investigated the therapeutic potential of vascular- targeted Poly-SA particles by evaluating their effect on neutrophil function during inflammation. Our results indicated that both targeted and untargeted Poly-SA particles modulate neutrophil recruitment to the site of inflammation. However, we found that vascular-targeted Poly-SA particles, depending on the specific vascular ligand used for coating, were more effective at reducing neutrophil infiltration to inflammatory sites compared to their untargeted counterparts. Additionally, (3) we developed rod-shaped Poly-SA particles to enhance neutrophil targeting through geometry-driven phagocytosis. The elongated shape of Poly-SA particles resulted in increased and more selective uptake by both human and mouse neutrophils, outperforming spherical Poly-SA particles. This greater uptake, combined with the elongated morphology of rod-shaped Poly-SA particles, led to a more significant reduction of neutrophil transmigration across endothelial barriers in vitro and in vivo compared to Poly-SA spheres. Finally, (4) we investigated a combinatorial therapy involving Poly-SA particles and antibiotic administration to treat bacterial-induced pneumonia. Our findings demonstrated that combining Poly-SA particles with antibiotics improved the treatment of bacterial pneumonia, notably decreasing neutrophil infiltration, bacterial load, and tissue damage in infected lungs. Overall, this dissertation demonstrates that optimizing particle parameters and integrating current clinical treatments can improve the therapeutic efficacy of particle-based systems, offering innovative options for more effective treatment of neutrophil-driven pathologies.