Biomedical Engineering Reference
In-Depth Information
O
O
S S
Recycling
G
S
S
Spacer
m
NH N
O
+
+
O
S
( )
n -2
O
Taxoid*
Linker
Taxoid*
m
O
S S
Taxoid*
Spacer
(2)
(1)
( )
m
n -2
(3)
GSH
Ligand
( )
GSH
Receptor
n -2
Taxoid*-bound
microtubule
Extracellular fluid
Cytoplasm
-tubulin
-tubulin
Taxoid*
FIGURE 20.5
(1) Internalization of the CNTs carried conjugate into the tumor cell via receptor-mediated
endocytosis. (2) Taxoid was released by the cleavage of the chemical linker. (3) The free taxoid
molecules were bound to microtubules to form stabilized microtubules, resulting in arrest of cell
mitosis and induction of apoptosis.
From [26] .
the nanotubes ( Figure 20.6 ). Transmission electron microscopy (TEM) has shown that the drug was
released after being transported into the tumor cell (HeLa cell) at the low pH of the lysosome but
not at the normal physiological pH of 7.4 ( [27] ) ( Figure 20.7 ). Recently, a novel approach has been
introduced by covalently attaching PAMAM dendrimers to FA-treated MWNTs. Using this approach
to delivery of nanotubes, flow cytometry and confocal microscopy have shown possible targeting of
cancer cells that overexpress FA receptors [28] .
20.3.2 CNTs as Carriers of Immunoactive Compounds, Proteins, and Genetic
Materials
The ability of macromolecules (e.g., gene) to cross the biological barriers and be expressed within
target cell is particularly difficult, owing to their high hydrophilicity and large molecular size. Gene
therapy aims to use genetic material to treat diseased cells by repairing the cause of the disease. Since
 
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