Biomedical Engineering Reference
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Fig. 10
Intracellular colocalization by fluorescence confocal microscopy. HeLa cells treated with
(
a
), NBD-PE labeled plain liposomes; (
b
), Rh123-liposomes.
1
,
4
: Cell treatment with PL or
Rh123-L in the green channel (Ex. 505 nm, Em. 530 nm);
2
,
5
: Cell staining treatment for visual-
ization of mitochondria with Mitotracker deep red in the deep red channel (Ex. 644 nm, Em.
665 nm);
3
,
6
: Merged
left
and
middle
panels and Hoechst stained nuclei (Blue channel. Ex.
385 nm, Em,. 470 nm).
Yellow color
indicates co-localization of mitochondria and Rh123-L.
Analysis of co-localization (Image J software) confirmed significant accumulation of targeted
liposomes in the mitochondria (Pearson's coefficient 0.55, Mander's coefficient 0.75 for Rh123-L
compared to Pearson's coefficient −0.083, Mander's coefficient 0.007 for plain liposomes)
(Grabowski
2008
; Zarate and Hopkin
2008
; van der Ploeg and Reuser
2008
).
The main approach for the treatment of LSD is enzyme replacement therapy (ERT)
based on the administration of exogenous enzymes (Grabowski and Hopkin
2003
).
This procedure remains limited in use and expensive because of poor delivery and
low stability of therapeutic enzymes. The use of liposome-immobilized enzymes
for ERT, was understood long ago (Gregoriadis
1978
). Lysosomes are also involved
in the cellular apoptosis due to the lysosome-dependent cell death pathway
(Kirkegaard and Jaattela
2009
). Moderate permeabilization of lysosomal mem-
branes can result in apoptosis of cancer cells (Boya et al.
2003
). Thus, delivery of
lysosome-destabilizing agents that cause cancer cell apoptosis may also benefit
from lysosome-targeted carriers.
We recently attempted to develop a lysosome-targeted drug delivery system
based on liposomes modified with a lysosome-specific ligand octadecyl deriva-
tive of rhodamine B (RhB). RhB is used to monitor membrane fusion (Hoekstra
et al.
1984
) and study lysosomal metabolism (Kuwana et al.
1995
). It has been
shown to specifically accumulate in the lysosomes of denervated skeletal muscle
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