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The internal crystalline structure of LCNP is conserved at the interfacial
layer upon adsorption as a distinctive Bragg diffraction peak is present in
neutron refl ectivity measurement (Vandoolaeghe et al., 2009b). The neutron
refl ectivity curve in Figure 10.7 shows that the intact CPNP binds to hydro-
philic surfaces with minimal collapsing and spreading for over 40 h. The curves
fi t very nicely to the cubic phase model with a repeating structure of 5.2 nm,
representing the cubic phase of the organized lipid molecules (Vandoolaeghe
(a)
10
0
bare surface
3.3 h
10
−1
15.3 h
28.7 h
34 h
39.2 h
44.8 h
10
−2
10
−3
10
−4
10
−5
10
−6
0.03
0.06
0.09
0.12
0.15
Q
(Å
−1
)
(b)
10
0
z
Layer adjacent to surface
Up to 3 layers:
d
surf
,
p
surf
,
§
surf
10
−1
10
−2
SiO
2
Si
p
10
−3
10
−4
10
−5
10
−6
0
0.03
0.06
0.09
0.12
0.15
Q
(Å
−1
)
Figure 10.7
Neutron refl ectivity,
R
, as a function of momentum transfer,
Q
, recorded
for adsorption of GMO-based LCNPs on hydrophilic silica: (a) in 0.1 M NaCl at pH
4.4 in D
2
O at different incubation times and (b) in D
2
O (fi lled squares) and Si contrast
matched water (open circles) at 45 h time. The solid lines correspond to the modeled
fi ts to the data using the cubic phase model, shown in the schematic drawing (inset),
where scattering density profi le is modeled as a sinusoid. [Reprinted with permission
from Vandoolaeghe et al. (2009b). Copyright 2009 by the American Chemical Society.]
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