Nanoparticles Enhanced Hyperthermia - Intracellular Delivery: Fundamentals and Applications - page 582

in conducting heat. There are various types of nanotubes, such as SWNTs and
MWNTs. SWNTs, a class of prototypical one-dimensional nanomaterials, possess
exceptional electronic and mechanical properties (Jorio et al. 2008 ). Most SWNTs
have a diameter close to 1 nm, with a tube length that can be many millions of
times longer. Alkali-halide salts, particularly potassium bromide, can reduce the
photothermal emission from SWNTs (Manning et al. 2003 ), so trapping salts inside
SWNTs and coating SWNTs with the salt has a more pronounced impact on reduc-
ing photothermal emission and therefore enhancing optical energy absorption
by SWNTs.
MWNT consists of multiple rolled layers of graphite, and Russian Doll model
(Galanov et al. 2002 ) and Parchment model can be used to describe the structures of
MWNT. Compared with the specific resonance absorptions of SWNTs, MWNTs
behave as highly efficient dipole antennae with broad absorption spectra, which
resulting in rendering them amenable to stimulation by a range of NIR energy
sources (Burlaka et al. 2010 ). Additionally, MWNTs as the metallic tubes can be
expected to absorb significantly more NIR irradiation because, per weight, SWNTs
contain both metallic and semiconducting ones. CNTs have extraordinary strength
and unique electrical (Minati et al. 2010 ), optical (Zhang et al. 2010 ; Lefrant et al.
2010 ) and thermal conduction properties (Savin et al. 2009 ).

3.2.6 Graphene

Grapheme is a one-atom-thick planar sheet. Since it was first created in 2004
by Geim and Novoselov at University of Manchester, researchers are amazed by
its unique properties. Recently, Acik et al. reported reduced graphene oxide can
strongly absorb infrared radiation (Acik et al. 2010 ). This implied that such kind
of material may have the possibility to provide better performance in PTT in the
future.

3.3 Latest Progress in Clinical Trials

3.3.1 DNA-Encasement Improves Carbon Nanotubes

The CNTs will stick to each other and self-associate, which limits the utility of
CNTs for in vivo use. The solution is to bind DNA to the CNTs. The studies on
DNA-encasement of SWNTs have demonstrated their feasibility and effect (Hughes
et al. 2007 ). For MWCNTs, it is more difficult to interact with DNA because they
have larger diameters than SWNTs and present a surface with a large radius of
curvature. Supratim et al have demonstrated that DNA-encasement enhance heat
production efficiency relative to non-DNA-encasement following NIR irradiation
of MWNTs, and DNA-encased MWNTs can be used to safely eradicate a tumor