Assessment of Charged AuNPs: From Synthesis to Innate Immune Recognition

Figure 4

Microscopic observation of AuNP interaction with human neutrophils. Whole blood was withdrawn intravenously from a 22-year-old adult in a healthy condition. Blood was mixed with EDTA (1 : 1 ratio) prior to its incubation with different charged NPs for 15 mins at 37°C in the presence of nitro blue tetrazolium (NBT) dye. Cells were then smeared and stained with eosin and methylene blue and observed under light microscopy. The cell density of polymorphonuclear (PMN) cells was relatively similar in both thick and thin smears, regardless of erythrocytes’ concentration. Black arrows point to PMNs. PBS: negative control; PMA positive control; poly(_L-lysine) (PLL): positively charged NPs; poly(vinyl alcohol) (PVA): negatively charged NPs; poly(ethylene glycol) (PEG): neutral NPs. Activated neutrophils exhibited formazan granules in the presence of PMA and PLL as further depicted in the enlarged inset. Scale bar: 10 μm ().