Biomedical Engineering Reference
In-Depth Information
(PPA) segment. This PEG-b-PPA copolymer carrier formed PIC micelles upon
condensation with plasmid DNA in aqueous solution. The PEG-b-PPA/DNA
micelles exhibited uniform and reduced particle size, ranging from 80 to
100 nm, and lowered the surface charge, compared with complexes of DNA
with the corresponding cationic PPA carrier. The PIC micelles maintained
similar transfection efficiency as PPA/DNA complexes, which was comparable
to that of PEI/DNA complexes in HepG2 cells, but yielded about 16-fold lower
transgene expression in primary rat hepatocytes than PPA/DNA complexes.
Following bile duct infusion in Wistar rats, PEG-b-PPA/DNA micelles
mediated four-fold higher and more uniform gene expression in the liver than
PPA/DNA complexes. Liver function tests and histopathological examination
indicated that PEG-b-PPA/DNA micelles showed low toxicity and good
biocompatibility in the liver. This study demonstrated the potential of PEG-b-
PPA/DNA micelles as an efficient carrier for liver-targeted gene delivery.
Kataoka et al.
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developed a supramolecular nanocarrier of siRNA from the
PEG-based block catiomer PEG-b-DPT carrying a diamine side chain with a
pK
a
directed to enhance intracellular gene silencing (Figure 9.17). The
distinctive polymer design managed both a sufficient siRNA complexation
and a buffering capacity of the endosomes. The PEG-DPT/siRNA PIC
micelles revealed remarkable knockdown of the endogenous gene, even after
serum incubation. Different PIC micelles of siRNA with PEG-DPT, PEG-
DMAPA, and PEG-PLL showed sufficient knockdown of the GL3 luciferase,
while the naked siRNA did not show any knockdown. These results indicated
that siRNA was successfully delivered into the cytoplasm. Notably, the gene
knockdown abilities of the PEG-DPT/siRNA PIC micelles were superior to
those of the other two complexes, especially at higher N/P ratios. The high
efficacy of PEG-b-DPT was attributed to the existence of additional secondary
amines with a lower pK
a
to promote the internalization of the siRNA
molecules into the cytoplasm through buffering of the endosomal cavity.
Similar results were also observed with the polyethylenimine-based polyplex
that showed an enhanced transfection efficiency at the higher N/P ratios.
d
n
4
y
3
n
g
|
7
Figure 9.17
Formation of PIC micelles by the block catiomer PEG-b-DPT and
siRNA.
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