The Scattering of Gold Nanorods Combined with Differential Uptake, Paving a New Detection Method for Macrophage Subtypes Using Flow Cytometery

The strategy of identification for M1 and M2 macrophages both in vivo and in vitro would help to predict the health condition of the individual. Here, we introduced a solution to this problem with the advantage of both the phagocytic nature of macrophages and the scattering effect of gold nanorods (GNRs). The internalized GNRs, relating to their extent of intake, caused a conspicuous scattering profile at the red channel in flow cytometry, overruling the contribution of the cellular side scatters. This internalization is solely governed by the surface chemistry of GNRs. The PAH-GNRs showed maximum intake potency followed by Cit-, PSS-, and PEG-GNRs. On a substantial note, PAH-GNRs lead to differential uptake between M1 and M2 cells, with three times higher intake in M2 cells over M1. This is the first report of employing the scattering of unlabeled GNRs to discriminate M1 and M2 cell types using a flow cytometer.