Effects of nanoparticle surface-coupled peptides, functional endgroups, and charge on intracellular distribution and functionality of human primary reticuloendothelial cells

The medical use of nanoparticles (NPs) has to consider their interactions with the cells of the reticuloendothelial system. In this study the authors used gold nanorods coated by PEG chains bearing peptides or charged functional groups to study their influence on the uptake, subcellular distribution, and activation of human primary reticuloendothelial cells: monocytes, macrophages (MΦ), immature and mature dendritic cells (DC), and endothelial cells (EC). We found that beside MΦ and immature DC also EC internalize large quantities of NPs and observed an increased uptake of positively charged particles. Most notably, NPs accumulated in the MHC II compartment in mature DC that is involved in antigen processing. Furthermore, surface-coupled peptide sequences RGD and GLF altered the activation profile of DC, and modulated cytokine release in both DC and MΦ in a cell specific manner. These data suggest that the charge of NPs mainly influences their uptake, whereas conjugated peptides alter cell functions. From the Clinical Editor: In this paper the interactions between RES cells and nanoparticles is investigated, concluding that in the case of gold nanorods charge determines uptake characteristics, whereas conjugated peptides determine their function.