Cationic Polymers for the Delivery of Therapeutic Nucleotides - Nanotechnology for the Delivery of Therapeutic Nucleic Acids - page 34

(25 kDa). In addition, these PEI derivatives did not have cell toxicity,
and the ester bonds were susceptible to hydrolysis.

32

Similarly, to
enhance the gene delivery efficiency and decrease cytotoxicity of
polyplexes, copolymers consisting of branched PEI (25 kDa) grafted
with Pluronic (F127, F68, P105) were successfully synthesized
by Liang The copolymers were tested for cytotoxicity, DNA

condensation, and complexation properties. Their polyplexes with
pDNA were characterized in terms of DNA size, surface charge,
and transfection efficiency. The complexes were of sizes below
300 nm, which implicated their potential for intracellular delivery.
The complex exhibited better condensation and complexation
properties than PEI 25 kDa, and cytotoxicity of PEI was strongly
reduced after copolymerization. These results demonstrate that
polyplexes prepared provided promising properties as stable, high
transfection efficiency vectors.

et al.

33
A series of PEI and γ-polyglutamic acid (PGA) nanocomposites
(PPGA) were prepared and evaluated by Tripathi On complexion

with pDNA, the positively charged PPGA/DNA nanocomposites
resulted in a higher level of

et al.

reporter gene transfection as
compared to native PEI and selected commercial reagents. These
nanocomposites also delivered siRNA efficiently into mammalian
cells. These results demonstrated the potential of the reported
nanocomposites for

in vitro

34

Similarly, low MW PEI was
grafted onto the block copolymer of PLL and PEG, yielding a ternary
copolymer PEG-b-PLL-g-PEI for gene delivery. Results indicate that
the copolymers to be a promising vector combining low cytotoxicity,
biodegradability, and high gene transfection efficiency.

in vivo gene delivery.

35
Branched PEI is capable of forming self-assembly complexes
with DNA to become a highly efficient agent for use in gene delivery.
Conjugation through the primary amines of PEI is an approach to
further enable the targeted delivery or to improve the stability of
the DNA-polymer complexes. Tseng

investigated the effects
of conjugation, folate, and the dextrans of MW 1500 and 10000 to
prepare three different types of PEI conjugates: dextran-PEI, folate-
PEI, and folate-dextran-PEI to form complexes with DNA. These
conjugates were able to deliver an estimated amount plasmid into
the cells and found to cause less cytotoxicity than the unmodified
PEI.

et al.

36

Similarly, with the aim to improve the specificity and to

reduce the cytotoxicity of PEI, Lee synthesized the conjugates

of the branched PEI (25 kDa) with transferrin (TF), a cell-binding
ligand. The transferrin-PEI (TP) conjugates were synthesized,

et al.