Lipoplexes and Polyplexes: From Gene Delivery to Gene Expression - Nanotechnology for the Delivery of Therapeutic Nucleic Acids - page 19

The necessity of more efficient synthetic gene delivery methods
prompted us to search for novel, less charged or non-cationic
gene delivery systems. Such systems would thus not be based
on electrostatic interactions with DNA. These non-electrostatic
complexes can be advantageous for applications,

since unlike cationic lipid/DNA complexes, the novel molecules could
not lead to a compacted state of DNA and therefore could potentially
lead to different kinetics of DNA release from complexes. Several
compounds are able to bind to double stranded DNA along the
grooves by formation of hydrogen bonds. Groove binding typically
exerts only subtle changes in DNA conformation, and DNA remains
essentially in the native form. Therefore, groove-binding complexes
will be essentially different from cationic lipid/DNA complexes, in
which DNA is compacted within a multi-lamellar bilayer. We have
set a prototype of new DNA vectors consisting of an amphiphile
able to bind to DNA through hydrogen bond interactions based on
Hoechst 33258 (

in vitro and in vivo

) (see Fig. 1.20), a well-known minor groove DNA
binding agent [41]. Thus, alkyl derivatives of Hoechst 33258 were
synthesized, and their complexes with DNA were characterized
using physico-chemical methods and included comparative studies
using known cationic lipid/DNA complexes for gene delivery. The
synthesis of dodecyl (

1

2 ) and octadecyl ( 3 ) carbamate derivatives of

1 are shown in Fig. 1.20.

N

N

N

i

N

H

N

H

N

H

N H

N

O H

O

O

R H

1 2 , R = ( C H 2 ) 11 C H 3

3 , R = ( C H 2 ) 17 C H 3

Figure 1.0 Non-electrostatic DNA binding lipids.

The physico-chemical characterization of complexes formed
between plasmid DNA and products 2 and 3 demonstrates a different
behavior of the new lipid/DNA complexes, as compared to previously
described cationic lipids, that typically compact DNA and retard
DNA in gel electrophoresis. The different nature of the presented
complexes and especially their unperturbed electrophoretical
mobility we have observed propose them as potential self-assembling
systems for gene delivery [42].