Hierarchically Organized Systems Based on Liquid Crystalline Phases - Self-Assembled Supramolecular Architectures: Lyotropic Liquid Crystals - page 161

surfactants (Engelskirchen et al., 2011; Mezzenga et al., 2005; Sagalowicz et al.,
2006b; Ubbink et al., 2008; Yaghmur et al., 2006a, 2009). Further details on the
nanostructural tuning of ISAsomes are provided elsewhere in this topic.
Temperature (Guillot et al., 2006; Yaghmur et al., 2010) or pressure
(Yaghmur et al., 2010) can be used to interconvert ISAsome nanostructures;
for instance, from H 2 to L 2 . The internal structure of ISAsomes can be also
triggered by changes in effective charge (Muller et al., 2010b; Salonen et al.,
2008, 2010b) or pH (Salentinig et al., 2010). It is possible to mix two different
types of ISAsomes and—due to the interparticle transfer of hydrophobic
molecules—one can create new types of ISAsomes different from either of
the starting ISAsomes (Moitzi et al., 2007). The rate of transfer can be modu-
lated by changing the ISAsomes' components; this feature is explained in more
detail in Section 6.4.
Liquid crystalline materials and their hierarchical structures have similari-
ties at the nanostructural level; however, the hierarchical structures have
certain advantages over the bulk systems: The consistency of the bulk phase
is broken in ISAsomes (by shear or ultrasonication), which eases their han-
dling, mainly due to reduced viscosity, and also reduces the effective cost by
utilizing less bulk material. The bulk phase is usually oil continuous; in con-
trast, ISAsome systems are water continuous and contain a variable volume
of water. These nanostructured assemblies are a well-known vehicle for drug
delivery as well as for the controlled release and uptake of functional mole-
cules (Garg et al., 2007; Hirlekar et al., 2010; Lee et al., 2009; Nguyen et al.,
2010; Rizwan et al., 2010; Sagalowicz et al., 2006a; Yaghmur and Glatter, 2009).
They fi nd further applications in the fi elds of pharmaceuticals and foods
since they can be made easily from food-grade or biocompatible components
(Mezzenga et al., 2005; Sagalowicz et al., 2006a; Ubbink et al., 2008; Yaghmur
and Glatter, 2009). ISAsomes act as bioadhesives (Geraghty et al., 1997) in
some applications, as they are (or can be made) biodegradable by simple
enzyme action.
The release and uptake rates of ISAsomes can be controlled by adding
certain gelling agents to the dispersion; this arrests the dynamics of the ISA-
somes by creating a hydrogel in the continuous water phase. ISAsomes
entrapped in thermoreversible hydrogels (Guillot et al., 2009b; Tomsic et al.,
2009) and their properties are discussed in Section 6.5. Recently, we have
shown that it is also possible to dry the ISAsome-arrested polymer matrix and
obtain a solid fi lm that can be later resolubilized to restore the ISAsomes
(Kulkarni et al., 2011a), as elucidated further in Section 6.5.
6.3 ISA SOMES STABILIZED BY NANOPARTICLES:
PICKERING EMULSIONS
Although surfactant stabilizers are widely used for stabilizing structured emul-
sions, including ISAsomes, they have certain disadvantages; for instance, they