Chemistry Reference
In-Depth Information
10
0
Bare surface
3.3 h
15.3 h
28.7 h
34 h
39.2 h
44.8 h
10
-1
10
-2
10
-3
10
-4
10
-5
10
-6
0.03
0.06
0.09
0.12
0.15
Q
(Å
-1
)
Figure 4.17
Neutron refl ectivity profi les at different time points for GMO cubosome
adsorption on an SiO
2
surface at a concentration of 0.05 mg/ml (Vandoolaeghe et al.,
2009b ).
using neutron refl ectometry (NR). Figure 4.17 shows evolving refl ectivity pro-
fi les for silica surfaces interacting with glyceryl monooleate (GMO) cubo-
somes recorded in D
2
O at different incubation times. The appearance of a
distinctive Bragg diffraction peak at
Q
- 0.12 Å
− 1
demonstrates the presence of
an organized repeating structure perpendicular to the plane of the surface,
which is thought to correspond to the ordered arrangement of lipid molecules
in the cubosomes. Different models were used in an attempt to optimize the
fi ts to the experimental refl ectivity profi les, all of them consisting of a single
layer adjacent to the surface with an adjoining layer with a repeating structure
with a total layer thickness of around 1500, which is close to the size of the
cubosomes.
They further used neutron refl ectometry to study exchange mechanisms
between cubosomes and lipid bilayers. A lipid exchange mechanism was pro-
posed that involved an initial absorption of material from the GMO cubo-
somes to form a mixed bilayer, and a subsequent release of material/particles
from the surface, as the uptake of GMO reached a maximum (Vandoolaeghe
et al., 2009).
Recently, Shen et al. (2010, 2011) studied phytantriol-based cubosomes
interactiong with 1 - palmitoyl - 2 - oleoyl - sn - glycero - 3 - phosphocholine (POPC)
bilayers. This system also showed growth of a Bragg peak even at high cover-
age of the POPC bilayer (98%), which is in contrast to the GMO study, where
the Bragg peak only appeared at low (55%) bilayer coverage. It was concluded
that the difference was due to incorporation of bilayer phospholipids within
the internal cubic structure of the nanoparticles, and hence the phytantriol-
Search WWH ::
Custom Search