Differential uptake of gold-nanorods promotes identification of M1/M2 subtype of macrophage by flow cytometry

摘要

Macrophages are one of the most important candidates of innate immune response with pronounced phagocytic activity.As a part of the defense mechanism of our system, an increased level of particular chemokines initiate the activation andfurther differentiation of the macrophages into two major phenotypes, M1 (classically activated) and M2 (alternativelyactivated). M1 macrophages promote ‘pro-inflammatory’ activities, whereas, M2 macrophages show ‘anti-inflammatory’activities. Now, normally a certain ratio of M1/M2 macrophages is maintained in healthy individuals. However, atcertain disease conditions, a shift in the M1 to M2 or M2 to M1 macrophage population is observed. An assessment ofthe M1/M2 ratio would readily predict the health condition of the individual. Here, we propose a novel approach toidentify M1 and M2 populations using simple flow cytometry and Gold nanorods (GNRs). According to reports,macrophages can readily internalize GNRs by phagocytosis. Now, this internalization of highly scattering GNRs willincrease the cellular scattering of macrophages and thus can be identified by the Flow Cytometric technique. For the firsttime, we are reporting about the differential uptake of polyallylamine hydrochloride (PAH) coated GNRs by M1 and M2macrophages (differentiated from THP1 cells). A 24 h incubation with the 100μg/ml PAH-GNRs results in a greaterintake of PAH-GNRs by M2 cells compared to M1, which leads to an increased side scatter for M2 cells in Flowcytometry. Overall, this study opens a new avenue for simple identification of M1 and M2 cell types.