Lipoplexes and Polyplexes: From Gene Delivery to Gene Expression - Nanotechnology for the Delivery of Therapeutic Nucleic Acids - page 18

that the reducible complexes
form normal complexes with DNA but when treated with reducing
conditions the complexes disrupt as expected. The complexes were
tested for expression of SEAP after incubation with 3T3-BALB/c
fibroblasts accompanied by cell viability assays using XTT kit as
compared to the known standard RPR-120535 (see Fig. 1.19). All
the polypeptides displayed low level of transfections (below 10%
of the activity of the standard RPR-12535); however, dendrimer
FIM-2126 displayed a substantially higher transfection efficiency as
compared to the standard RPR-120535.
We acknowledge that all the products disclosed no significant
toxicity at any charge ratio as compared to previously developed
synthetic agents (similar levels as shown for FIM-2126). We conclude
that the introduction of the degradable disulfides along polycationic
peptide chains brings about a substantial reduction in toxicity at any
charge ratio and for any of the disulfide containing polypeptides,
however the complexes displayed moderate transfection probably
due to early release of the DNA from the complex upon cell entry.
On the other hand, the dendrimer product displayed substantial
transfection efficiency. We have measured the size of some of the
complexes used for transfection, and, interestingly, the complex
dendrimer/DNA disclosed a size of about 20-40 nm, while the
polycationic peptides displayed sizes of about 200-800 nm. We
conclude that polycationic peptides should be long enough so that
DNA can be released at a slower rate [37].

These results proved in vitro

1. Towards Non-Electrostatic DNA

Complexing Agents

Cationic lipids, cationic polymers, and cationic peptides (histone
sequences) form compacted complexes with DNA. Along the dife-
rent approaches, many advantages have been demonstrated for a
variety of cationic entities, linkers, and lipids.
Nevertheless, the possibility exists to complex DNA through
proton donor and proton acceptor non-electrostatic interactions
with DNA-grooves. This type of non-electrostatic complexes has
been developed especially for sequence-specific binding to DNA
and not for gene delivery. Several prominent works were recently
accomplished in this field [38-40].