Chemistry Reference
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In this context, toward the design of an advanced drug delivery system
based on light-triggered phase transition of liquid crystalline phases, Fong
et al. (2010) reported the design of novel liquid crystalline matrix-gold nanorod
hybrid materials. Hydrophobized gold nanorods (GNRs) have been incorpo-
rated within the liquid crystalline matrix, composed of phytantriol and water,
to provide remote heating and trigger the phase transitions on irradiation at
close to their resonant wavelength. The surface of plasmonic metal nanopar-
ticles delivers heat into surrounding material on exposure to an appropriate
light source at the plasmon resonance. The application of near-infrared-
sensitive nanorods has signifi cance in designing systems for ophthalmic, sub-
cutaneous, or deeper tissue applications. These investigators used plasmonic
nanoparticles to achieve reversible phase transitions, hence offering a novel
practical solution. The presence of nanorods at concentrations up to 3 nM did
not change the lattice parameter of cubic (v
2
), hexagonal (H
II
), and micellar
(L
2
) systems in the absence of laser irradiation.
Irradiation of the system [at 808 nm near-infrared (NIR) diode laser], on
inclusion of a low concentration of GNRs (0.3 nM) in the matrix, did not
induce a change in phase structure away from the Pn3m bicontinuous cubic
phase. However, a small decrease in lattice dimension occurred, indicating that
heating of the matrix has occurred. The structure relaxed back to the original
position when the laser was off. On repeated application of the 5-s laser pulse,
the system again displayed the heating effect and relaxed back to the start-
ing position when irradiation was complete (Fig. 8.16). This contraction and
80
L
2
70
H
2
O
2
+H
2
60
50
O
2
40
30
20
Laser On
Off
Laser On
Off
10
0
5
10
15
20
25
30
Time (s)
Figure 8.16
Effect of laser irradiation on apparent temperature of the phytant-
riol
0 nM are white
symbols, 0.3 nM blue symbols, 1.5 nM yellow symbols, and 3 nM black symbols. Circles
indicate v
2
phase, triangles indicate v
2
+
water matrix (
T
app
) with change in GNR concentration. [GNR]
=
L
2
, and diamonds
indicate L
2
. The cartoon on the right indicates the type of phase structure present with
increasing temperature (Fong et al., 2010).
+
H
2
, squares indicate H
2
+
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