Biomedical Engineering Reference
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Fig. 9 ( a ), Fluorescence microscopy showing internalization of Rh-PE-labeled-TATp containing
liposomes internalization by U87 MG astrocytoma. 1 : 9 mol % pH-non-sensitive PEG-PE at pH
7.4, 2 : 9 mol % pH-sensitive PEG-Hz-PE after incubation at pH 5.0 for 20 min. The cleavable
(pH sensitive) PEG-PE-based TATp-containing liposomes kept at pH 7.4-8 show only a marginal
association with cells while those preincubated for 20-30 min at pH 5.0 demonstrated a dramati-
cally enhanced association with the cells (higher fluorescence). ( b ), Fluorescence microscopy
images of LLC tumor sections from tumors injected with pGFP-loaded TATp-bearing liposomes.
3 : using a pH-non-cleavable PEG coat, 4 : with a low pH-cleavable PEG coat
Mitochondria represent an important target for intracellularly delivered drugs and
DNA. Mitochondrial dysfunction contributes to a variety of human disorders, ranging
from neurodegenerative diseases, obesity, diabetes, ischemia-reperfusion injury and
cancer (Wallace 1999 ). The number of diseases is also found to be associated with
defects of the mitochondria genome has grown significantly over the past decade.
Mitochondria also play a key role in the complex apoptosis mechanism. The mecha-
nism of paclitaxel induced apoptosis is believed to be by stabilization of microtubules
of cells (Fan 1999 ; Wang et al. 2000 ). It has been also observed that there is a 24 h
delay between paclitaxel-induced release of cytochrome c in intact cells versus cell-
free system (Andre et al. 2002 ). This could be due to only few drug molecules reach-
ing the mitochondria. Hence, we hypothesized that we could improve the apoptosis
due to paclitaxel if we could delivery paclitaxel to mitochondria.
The mitochondrion has a major role in the metabolism of eukaryotic cells in the
synthesis of ATP by oxidative phosphorylation via the respiratory chain. This process
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