Figure 7
From: Single wall carbon nanotubes enter cells by endocytosis and not membrane penetration
FLIM of cytoplasmic GFP and GFP-tagged endosomes in cells exposed to SWCNTs. (A) Addition of SWCNTs was associated with a decrease in GFP mean fluorescence lifetime (Ď„m, pseudo-colored red to green to blue). This change in Ď„m was most obvious at the periphery of the cell and moved inward over longer times, as seen by more internal green regions and a more severe quenching (green to red) at the periphery. (B) Expression of soluble GFP in the cytoplasm also showed a reduction in Ď„m upon incubation with SWCNTs. (C) Treatment of cells with long SWCNTs (1250 nm vs. 145 nm) showed little change in the GFP-endo Ď„m. (D) Quantification of the Ď„m revealed time-dependent behavior. The Ď„m of GFP-endo is significantly (p < 0.01) reduced after 5 min of SWCNT exposure but recovered to near control levels after 25 min of exposure. Similarly, the Ď„m of cytoplasmic GFP significantly (p < 0.01) decreased after 5 min of SWCNT treatment; however, unlike GFP-endo, it remained quenched after 25 min of exposure to SWCNTs. The Ď„m of GFP-endo, when exposed to long SWCNTs was relatively unchanged.