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(Left panel) Schematic of the present study, showing quenching of FBI fluorescence as a result of energy transfer from the proteins to their CNT substrate and translocation of CNT-FBI across a cell membrane. (Right panel) SEM images of SWNT bundles, SWNT-FBI coronas (top panels), MWNTs, and MWNT-FBI coronas (bottom panels). Scale bar: 200 nm for all panels.
(a) Normalized absorbance curves showing the stability of CNT-FBI coronas for both SWNTs (blue diamonds) and MWNTs (red circles) over 10 h. (b) Fluorescence intensities of free, labeled FBI supernatants obtained from pelleting SWNT-FBI (blue curves, 10, 40, and 80 μg/ml of the SWNTs) and MWNT-FBI coronas (red curves, 100, 400, and 800 μg/ml of the MWNTs). The fluorescence intensities decreased with increased nanotube concentration for both samples. (c) Stern-Volmer plots show quenching coefficients of 32.7 and 8.8 for SWNT-FBI and MWNT-FBI coronas, respectively. I 0 and If : fluorescence intensities of the labeled FBI control and the CNT-labeled FBI mixture, respectively. CNT concentrations: 0.02 to 0.08 mg/ml.
HT-29 cell uptake of CNT-FBI coronas overlaid from bright field and confocal fluorescence images. (a) and (b) Controls of labeled FBI fluorescence and HT-29 cells. (c) and (d) Controls of SWNT-FBI and MWNT-FBI showing fluorescence quenching. (e) Cell adsorption of SWNT-FBI and FBI fluorescence recovery in the intracellular space (arrows). (f) Pronounced cell adsorption and dissociation of MWNT-FBI in the extracellular space indicated by fluorescence recovery. Cell damage induced by MWNTs is evident. Scale bar: 10 μm for all images.
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