Neutrophils preferentially phagocytose elongated particles—An opportunity for selective targeting in acute inflammatory diseases

Polymeric particles have recently been used to modulate the behavior of immune cells in the treatment of various inflammatory conditions. However, there is little understanding of how physical particle parameters affect their specific interaction with different leukocyte subtypes. While particle shape is known to be a crucial factor in their phagocytosis by macrophages, where elongated particles are reported to experience reduced uptake, it remains unclear how shape influences phagocytosis by circulating phagocytes, including neutrophils that are the most abundant leukocyte in human blood. In this study, we investigated the phagocytosis of rod-shaped polymeric particles by human neutrophils relative to other leukocytes. In contrast to macrophages and other mononuclear phagocytes, neutrophils were found to exhibit increased internalization of rods in ex vivo and in vivo experimentation. This result suggests that alteration of particle shape can be used to selectively target neutrophils in inflammatory pathologies where these cells play a substantial role.