Manipulating Nanoparticle Aggregates Regulates Receptor-Ligand Binding in Macrophages

Abstract

The receptor-ligand interactions in cells aredynamically regulated by modulation of the ligand accessibility.In this study, we utilize size-tunable magnetic nanoparticleaggregates ordered at both nanometer and atomic scales. Weflexibly anchor magnetic nanoparticle aggregates of tunable sizesover the cell-adhesive RGD ligand (Arg-Gly-Asp)-active materialsurface while maintaining the density of dispersed ligandsaccessible to macrophages at constant. Lowering the accessibleligand dispersity by increasing the aggregate size at constantaccessible ligand density facilitates the binding of integrin receptorsto the accessible ligands, which promotes the adhesion ofmacrophages. In high ligand dispersity, distant magnetic manipulation to lift the aggregates (which increases ligand accessibility)stimulates the binding of integrin receptors to the accessible ligands available under the aggregates to augment macrophageadhesion-mediated pro-healing polarization both in vitro and in vivo. In low ligand dispersity, distant control to drop the aggregates(which decreases ligand accessibility) repels integrin receptors away from the aggregates, thereby suppressing integrin receptor-ligand binding and macrophage adhesion, which promotes inflammatory polarization. Here, we present "accessible ligand dispersity" as a novel fundamental parameter that regulates receptor-ligand binding, which can be reversibly manipulated by increasing and decreasing the ligand accessibility. Limitless tuning of nanoparticle aggregate dimensions and morphology can offer further insight into the regulation of receptor-ligand binding in host cells