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when interacting with the surface (Dong et al., 2011). The HPNPs show faster
adsorption kinetic and free energy gain upon particle adsorption due to the
release of internal stress from the unfavorable internal packing geometry.
Once adsorbed on the surface, HPNPs may experience greater structural
relaxation and spreading than the CPNPs, which can lead to a lower quantity
of adsorbed HPNPs. This is consistent with the high viscosity of liquid crystal-
line cubic phases compared to the hexagonal phase (Larsson, 1989).
The adhesion strength of the nanoparticle was found to be dependent on
the lipid system (Dong et al., 2011). GMO-based CPNP showed weaker surface
adhesion compared to the phytantriol (PHYT)-based CPNP even though the
same stabilizer, Pluronic F-127, stabilizes both types of CPNPs. The difference
in the adhesion strength was proposed to be dependent on the different inter-
actions between the Pluronic stabilizer and the lipid crystalline structure. It is
believed that the hydrophobic domain of Pluronic anchors to the crystalline
particle, either by direct adsorption or by interpenetration into crystalline
phases, thereby allowing the hydrophilic chains to extend into the surrounding
bulk water to provide steric stabilization (Dong et al., 2011; Kaasgaard and
Drummond, 2006). It has been proposed that strong interdigitation between
Pluronic and GMO-based CPNP inhibits strong particle adsorption and results
in weak particle surface adhesion. On the other hand, Pluronic loosely adheres
on the surface of PHYT-based CPNP, which can be easily displaced to allow
strong particle adhesion with the surface. The PHYT-based CPNP has been
shown to withstand extensive agitation, which may be of interest for agricul-
ture applications where mechanical resistance is desirable.
10.5
FORMATION OF SURFACES
Formation of liquid crystalline structures on surfaces can be obtained in many
different ways. Depending on the desired application and result, different
methods can be utilized, ranging from adsorption and deposition of liquid
crystalline particles to the formation from chemical reaction.
10.5.1
Adsorption of LCNP
One of the most convenient methods to form a crystalline structure on a
surface is through adsorption of LCNP. The use of stabilizer preserves
the liquid crystalline structure of LCNP in a dispersed form, which in turn
allows easy delivery and application. The property of the particle stabilizer,
solution condition, and also surface chemistry can signifi cantly affect the
adsorption interaction. Studies have shown strong adsorption dependence on
physical parameters such as particle size, ionic strength, and pH conditions
(Svensson et al., 2008a,b; Vandoolaeghe et al., 2006, 2008, 2009b,c). GMO-
based cubic LCNP stabilized with Pluronic F-127 was found to adsorb intact
on hydrophilic silica in the presence of an electrolyte, except at high alkaline
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