We use fluorescence lifetime imaging microscopy (FLIM) to analyze binding and internalization of gold nanoclusters (AuNCs) on/in cells. FLIM is a powerful method to discriminate between emitters of different fluorescence lifetimes. AuNCs with mercaptoundecanoic acid as the stabilizing ligand (MUA-AuNCs) show a fluorescence emission that peaks at a wavelength around 525 nm, which is in the same wavelength region as the autofluorescence of a biological cell. However, the fluorescence decay time of the MUA-AuNCs (100 ns) is much longer in comparison to the autofluorescence (3 ns). We biofunctionalize these MUA-AuNCs with an aptamer that specifically binds to the interleukin-6-receptor expressed on the cell's membrane. To get an image of the whole cell and the bound and internalized AuNCs we use cross-sectional FLIM scans in axial direction at different heights through the cell. With this technique we are able to visualize specifically bound and internalized aptamer-MUA-AuNCs using different FLIM methods and compare the results with semi-empirical simulations. Figure 1 (a) shows the FLIM image of a cell incubated for 10 min with the aptamer-MUA-AuNCs. The clusters (green) are attached on the cell’s membrane. In contrast, the FLIM image in figure 1(b) shows a cell incubated twice for 10 min with internalized AuNCs. By varying the incubation time we are able to distunguish the binding and internalizing of the aptamer-MUA-AuNCs.

Fluorescent gold nanoclusters on/in cells visualized by fluorescence lifetime imaging microscopy

254th National Meeting (2017)

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