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Fig. 26 Photothermal heating of passively targeted AuNRs in tumors. PEG-AuNRs or saline was
given i.v. to mice bearing MDA-MB-435 tumors on opposing flanks. After AuNRs had cleared
from circulation (72 h after injection), the right flank was irradiated (beam size indicated by
dotted
circle
). Figure reprinted with kind permission from [
187
]
the three-dimensional distribution of PEG-NRs in tumors, showing clear distinc-
tion between AuNRs and soft tissues, as seen in Fig.
26
.
To prolong the circulation time, optimize the tumor targeting, and decrease the
liver uptake, Choi et al. prepared AuNR-loaded, chitosan-conjugated, pluronic-
based nanocarriers which could serve as imaging agents for cancer cells and as a
very effective hyperthermia agent for PTT [
184
]. By delivering the nanocarriers via
an intravenous injection followed by NIR laser irradiation to the tumor site resulted
in a very efficient thermolysis in vivo, achieving a complete tumor resorption
without damage to the surrounding tissue.
Xia and coworkers studied AuNCs as photothermal transducers for therapeutic
applications [
104
,
144
,
169
-
171
]. They utilized PEGylated AuNCs with an edge
length of 45 nm for selective destruction of neoplastic tissue using a bilateral tumor
model. The particles accumulated in tumors with a relatively high efficiency
leading to a slightly higher amount of AuNCs in the tumor periphery than in the
inner core. With an infrared camera the temperature increase during photothermal
treatment was monitored which is shown in Fig.
27
.
The effect of PTT on cells by larger, more rapid temperature increases, often
referred to as “ablative” treatments, is considered to be necrosis with the
corresponding melting of cell membranes and organelles [
188
]. In contrast to that
mild temperature increases (known as hyperthermia), mostly proceed via apoptotic
pathways, and are known to perturb a variety of normal cellular functions
[
183
]. Huang et al. designed AuNR elastin-like polypeptide matrices loaded with
the heat shock protein (HSP) inhibitor 17-(allylamino)-17-demethoxygel-
danamycin (17-AAG) to give insights into the release of heat shock proteins
(HSPs), which help to restore normal processes to the cell, and their relation to
PTT [
181
]. They demonstrated that AuNRs in combination with 17-AAG improve
significantly (
90%) death of cancer cells, while “single treatments” (i.e., hyper-
thermia alone and 17-AAG alone) demonstrated minimal
>
loss of cancer cell
