Surface Chemistry Controls the Uptake of Gold Nanorods by Macrophages

In recent days gold nanorods (GNR) catch the eyes not only with their unique optical behavior but also for a wide variety of application in the field of the diagnostics and therapy. When it comes to the case of in vivo studies, monitoring the pattern of the interaction of nanoparticles with the immune cells are very important. Macrophages, the proficient phagocytic immune cells, differentiated from monocytes, play a major role in our innate immunity. Recently macrophages after uptake of nanoparticles are used as a vehicle for drug delivery for cancer or, as a diagnostic tool for atherosclerosis. Though macrophages can internalize the GNRs by phagocytosis, still the surface charge and presence of particular linker can bring a huge change in the uptake and cytotoxicity pattern of GNRs. In this study, we took three different types of macrophages –macrophages isolated from blood of the healthy donor, macrophages differentiated from THP1 human monocyte cell lines and RAW 264.7 murine macrophage cell line and compared their change in viability and uptake of GNRs. We chose GNRs of same aspect ratio with different zeta potential. GNRs with positive zeta i.e. cetyl trimethylammonium bromide(CTAB), poly allylamine hydrochloride (PAH) internalized more than the GNRs with null i.e. poly ethylene glycol (PEG) or negatively charged surface i.e., poly sodium 4-styrenesulfonate (PSS), citrate. But because of high toxicity CTAB GNRs effect on cell viability, whereas PAH GNRs showed less toxicity.Overall RAW 264.7 showed more uptake than macrophages from PBMC. This study draws an idea of how surface modifications of GNRs affect their uptake by macrophages.