Page 140 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

138 CHAPTER 6 Laser-assisted cancer treatment

presence of silica on the surface improves further modification by employing silane
coupling reactions. To increase the PTT efficiency, the large amounts of GNRs need
to accumulate in the desired region. Several approaches have been studied to meet
this goal, one of which was layer-by-layer assembly techniques composed of posi-
tive charged layer of poly(diallyldimethylammonium chloride) and negative charged
layer of poly(sodium-p-styrenesulfonate). Qiu et al. claimed that the self-assembled
GNR increased the nanoparticles accumulation and reduced the toxicity compared to
nonassembled GNR [24].

6.2.3 Gold nanocage
GNCs with hollow interiors and porous walls were first introduced by Sun et al. The
general method to synthesize GNCs is based on galvanic replacement reaction which
occurred between nanocubes like silver template and gold precursor. The difference
in electrochemical potential between these two leads to the depositing of the gold
nanoparticles on the template. The SPR peak adjusts in the range of 600–1200 nm
by controlling the amounts of precursors. Some studies focused on the application of
GNS in PTT are reviewed in Table 6.1.
Not only GNSs have been used for PTT but also considered for dual PTT/PDT.
Khlebtsov et al. functionalized the surface of silica-coated GNCs using a PDT sen-
sitizer, Yb-2,4-dimethoxyhematoporphyrin [29]. Their introduced nanocomposite
produced both free radical oxygen and heat during laser emission. Also, the pres-
ence of Yb-2,4-dimethoxyhematoporphyrin in the structure exhibited NIR lumi-
3+
nescence originated from Yb . In another study, hypocrellin B photosensitizer was
incorporated into the lipid-coated GNCs [30]. Synergistic PTT and PDT effects were
observed during pulse laser irradiation on HeLa cells.

6.2.4 Gold nanostars
GNSTs are novel stars shape nanoparticles composed of a small core and multiple
sharp tips, the optical properties of which related to the size of the tips. The strong
SPR effect of GNSTs is mainly related to the SPR difference between the core and
the tips. The main method to produce GNSTs is typically seed-mediated growth
method or seedless procedure using 2-[4-(2-hydroxyethyl)-1-piperazinyl] ethanesul-
fonic acid (HEPES) having a role of both reducing agent and shape controller. The
main studies of using GNSTs in PTT summarized in Table 6.1.

6.2.5 Carbon nanotubes
Compared to metallic nanoparticles, carbon nanostructures have several advantages.
First, the large number of functional groups which allow proper surface modification
to increase stability and blood circulation, thereby increasing drug accumulation in
the tumorogenic side. Second, strong optical absorption in NIR region with high
penetration depth to soft tissues.