Cationic Polymers for the Delivery of Therapeutic Nucleotides - Nanotechnology for the Delivery of Therapeutic Nucleic Acids - page 33

transfection efficiency than PEI alone and also coupled with better
biocompatibility and no cytotoxicity.

27
Linear PEI (LPEI) with a MW of 22 kDa has superior ability to
induce gene transfer compared to its branched form. However, the
transfection efficiency of the polymer cannot be enhanced beyond
a certain limit due to cytotoxicity. Breunig explored LPEI with

MW ranging from 1.0 to 9.5 kDa to overcome this limitation. Results
suggested that LPEI with low MW are promising candidates for non-
viral gene delivery. They are more efficient and substantially less
toxic than their higher MW counterparts.

et al.

28

reported low
MW PEI (LMW-PEI) linked to an expressing plasmid containing a
green fluorescence protein reporter gene for effective gene transfer
in CM7221 cell line. Relationship among the MW, structure of PEI,
their transfection activity, and cytotoxicity was studied. Results
showed that LMW-PEI/DNA complexes led to high levels (about
55%) of expression in the CM7221 cell line. However, with the
increasing of PEI MW, the transfection activity of PEI was decreasing
and simultaneously there was an increasing cytotoxicity with these
larger PEI molecules.

Liu et al.

29

studied the influences of plasmids factor, albumin, serum,
cell density, operation methods, and PEI/DNA preserve factors
on transfection efficiency. Linear plasmids lowered transfection
efficiency. Serum and albumin in the culture medium decreased
the transfection efficiency of PEI/DNA. Freezing of PEI/DNA
complexes significantly decreased transfection efficiency. Thus, with
PEI, optimal and reduplicate transfection results could be obtained
by controlling related factors.

Li et al.

30

reported LPEI (25 kDa)
nanoparticles (LPN) series cross-linked with 1,4-butanediol
diglycidyl ether. Size, surface charge, morphology, pDNA protection/
release, cytotoxicity, and transfection efficiency of LPN was studied.
These LPN showed increased buffering capacity with increasing
cross-linking and also exhibited excellent transfection efficiency
in comparison with LPEI and the commercial transfection agents.
These particles were relatively non-toxic

Goyal et al.

in vitro (in cell lines) and in

vivo gene expression studies in Balb/c mice

showed maximum expression of the reporter gene in the spleen.

(in Drosophila). In vivo

31
Synthesized PEI derivatives are more advantageous over
conventional PEI for gene delivery. Forrest

reported ester
cross-linked PEI derivatives prepared by reacting PEI (800 Da) with
small diacrylates mediates gene expression more efficiently than PEI

et al.