Schematic illustration of the ways that particle physicochemical characteristics can influence degrees and conformation of adsorbed proteins. Surface curvature, topography, hydrophilic/hydrophobic chemistry and polymer coating steric barriers on nanoparticle surfaces are shown to alter amounts and conformations of proteins adsorbed to surfaces. Surface-adsorbed proteins (opsonins) influence macrophage recognition and uptake of nanoparticles [28, 32, 91]. Additionally, conformational protein rearrangements on nanoparticle surfaces alters protein epitope exposures to phagocytes [83, 84]. Certain epitopes have the capacity to activate macrophages[31].