The scattering of gold nanorods in identification of macrophages

Currently, gold nanorods (GNRs), with versatile optical behaviors, are in the immense study to achieve a variety of applications in the fields of diagnostics and therapy. Macrophages, the proficient phagocytic immune cells, mainly differentiated from monocytes, play a major role in our innate immunity. Depending on the state of a disease, an enhancement of local macrophage population occurs as a normal protective measure of our body. We want to monitor this increased level and use it as a prediction index of a disease. The advantage of working with macrophages is that they willingly internalize GNRs by phagocytosis. Now, the macrophages with GNRs can be identified by Flow Cytometric technique through the high scattering of GNRs. Moreover, the surface charge of GNRs can significantly change the uptake and cytotoxicity pattern of GNRs. Here we compared the uptake of GNRs, with different zeta potentials, among three different types of macrophages-macrophages isolated from the blood of a healthy donor; macrophages differentiated from THP1 human monocyte cell lines and RAW 264.7 murine macrophage cell line. GNRs with positive zeta i.e. cetyl trimethylammonium bromide (CTAB), poly allylamine hydrochloride (PAH) higher uptake than the GNRs with null zeta i.e. polyethylene glycol (PEG) or negatively charged surface i.e., poly sodium 4-styrenesulfonate (PSS) and citrate. Overall, this study showed an application of the scattering property of GNRs as a tool to identify macrophages and how modifications of the GNR surface monitor their uptake by macrophages.