Recent Developments in Lyotropic Liquid Crystals as Drug Delivery Vehicles - Self-Assembled Supramolecular Architectures: Lyotropic Liquid Crystals - page 234

measurements, is consistent with a dehydration of the GMO hydroxyl groups,
that is, a breakage of hydrogen bonds between GMO polar groups caused by
the presence of the highly polar DNA. Additionally, the modifi cations within
the vicinity of the GMO-water interface imply a less ordered state with the
increased content of gauche conformations, which is again coherent with the
shrinkage of the H II cylinders.
According to Amar-Yuli et al. (2011a), these results indicated that the DNA
is confi ned within the aqueous domains of the H II cylinders, stabilized by
hydrogen bonds with the water and/or GMO head groups, and leading to an
observable rupture of the H bonds in the H-bond donor part of the GMO
polar heads (OH) and a decrease in the frequency of the H-bond acceptor
bands of the GMO polar heads (CO-O). The role of DNA in this case is thus
consistent with moving away bound water from the interfacial region of the
water channels.
Examination of the second H II system, which contains the cationic surfac-
tant oleyl amine, shows very moderate changes upon incorporation of DNA
in all the bands considered when compared to the nonionic mesophase. These
data clearly suggested that in the presence of a cationic surfactant decorating
the interface of the water channels, the interactions between the lipid polar
heads and DNA change in nature, as the hydrogen bonding of D 2 O and the
GMO polar heads, is mostly unaffected by the presence of DNA. It was
inferred that the DNA is confi ned in the water channels as well as in the cat-
ionic H II mesophases, and electrostatically bound to their surfaces.
The DNA cumulative release profi le from the two mesophases is depicted
in Figure 8.12, which illustrates the difference in release rate from the nonionic
and cationic H II host mesophases. While practically no release of DNA mol-

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Time (days)

Figure 8.12 Release profi le of DNA from the two columnar H II mesophases consid-
ered: release from the nonionic system (fi lled circle, GMO-tricaprylin-water-ascorbic
acid) and release from the cationic-based columnar hexagonal phase (open circle,
GMO/oleyl amine-tricaprylin-water/ascorbic acid) at room temperature (Amar-Yuli
et al., 2011a ).