Biomedical Engineering Reference
In-Depth Information
20.2
CELLULAR UPTAKE OF CNTS
The cellular uptake of CNTs has been confirmed in a range of studies but the mechanism of CNT
penetration into cells is still not well-understood. Because of their needle-like shapes, CNTs might be
able to perforate cellular membrane into the cellular components without causing apparent cell dam-
age (
[2,3,7-9]
). An
in vitro
CNTs nanoinjector system has been developed by Chen and coworkers
[5]
. The nanoinjector was designed using an atomic force microscope (AFM) tip and functionalized
MWNTs attached to a model cargo compound via a disulfide linker. The MWNTs nanoinjector suc-
cessfully transported into the cell where the disulfide bond was broken, resulting in the release of the
cargo compound within the cytosol (
Figure 20.2
).
The perpendicular positioning of the nanotubes to the cell membranes suggests that uptake of
CNTs was similar to that of nanoneedles which diffuse through cell membrane without causing cell
death (
[4]
) (
Figure 20.3
). In a study conducted by Kam and coworkers
[10]
, fluoresceinated protein
attached to SWNTs-biotin was detected in the endosomes, suggesting that uptake of the nanotubes
occurred via endocytosis. By contrast, no protein was internalized in the absence of nanotubes. Using
epifluorescence and confocal microscopy, functionalized CNTs labeled with a fluorescent agent have
shown to penetrate through the cell to cytoplasm or the nucleus of fibroblasts
[2]
. In another study,
it has been reported that the uptake mechanism of MWNTs is highly dependent on the length of
Cell exterior
SH
SS
SS
SH
HS
HS
Cytosol
FIGURE 20.2
A schematic diagram showing that an AFM-controlled MWNT-based nanoinjector was able
to penetrate into a cell and release the attached cargo compound after the breakage of
the disulfide bond. This was followed by successful retraction of the nanoinjector with no
apparent cell damage being produced.
From
[5]
.
