Isomeric Differences in Nanoparticle’s Surface Chemistry Alter Macrophage Interactions In Vitro Due to Protein Corona

The interactions
of nanoparticles (NPs) with macrophages
after
intravenous injection are critical in determining their biodistribution
and pharmacokinetics. The formation of protein corona (PC) on the
nanoparticles, often a result of NP-plasma protein interactions, influences
macrophage response, thereby directly determining the NPs’
fate in vivo. While the effect of NPs’ surface
chemistry on protein corona formation and macrophage interaction is
extensively studied, the results are often confounded by the effects
of surface charge and hydrophobicity. Therefore, to assess the impact
of NPs’ surface chemistry alone on protein corona and NP-macrophage
interactions, we developed gold (Au) NPs surface-modified with the
isomeric amino acids leucine (Leu) and isoleucine (Iso Leu), which
have similar isoelectric points and hydropathy indices. The synthesized
NPs had similar sizes, zeta potentials, hydrophobicities, and morphology.
Incubation of the NPs in plasma under flow conditions resulted in
a protein corona (PC) that differed in amount and composition. Pathway
analysis showed that these variations in the PC corresponded to the
activation of different phagocytic and inflammatory pathways. These
in silico analyses were confirmed in macrophages, which showed higher
uptake of the Leu-AuNP-PC complex compared to Iso Leu-AuNP-PC and
a corresponding increase in inflammatory cytokines. These studies
demonstrate the sensitivity of the PC to subtle changes in the surface
chemistry of NPs, which could have significant in vivo implications
for the clinical application of NPs.