Figure 7

Broadness of cell ROI spectra. Cells were exposed to 12, 24, 48, or 96 μg/mL of AuNPs for 2, 5, 10, or 24 h. Spectral broadness was defined as the spectral width at 95% of maximum intensity (‘spectral width’). Spectral width increased significantly after 24 h of exposure (** denotes p < 0.01). Shown are the mean and standard error of the mean. For each condition, spectra were analyzed from 63 to 125 cells. The percent of cells exhibiting sufficient NP signal for analysis is also plotted. At low exposure dose and duration, only a small proportion of cells in the cell population displayed sufficient NP signal since most cells had not yet internalized a substantial number of NPs at this time. Spectral width was only analyzed for cells containing sufficient NP signal (not dominated by cell scattering); see Additional file 1 for details. Thus, at low exposure doses and durations, the spectral width measurements reflect only the small subset of cells that had internalized NPs and thus had sufficient NP signal to be analyzed.