Biomedical Engineering Reference
In-Depth Information
2
Gold Nanoparticles
In the majority of experimental approaches, photosensitizers have a limited
solubility in water. Thus, these molecules require a vehicle to deliver the drug to
the tumor tissue, and gold nanoparticles (AuNPs) can play this role. One major
advantage of AuNPs is their chemical inertness and their biocompatibility. The
functionalization of the surface of the AuNPs with the PS requires the existence of
interactions between the two components. These interactions can be covalent
bonds or weak interactions such as van der Walls interactions and electrostatic
interactions.
2.1
Phthalocyanines Gold Nanoparticles Conjugates
Phthalocyanine (Pc) derivatives are tetrapyrrolic macrocycles which can be used for
PDT. These molecules upon irradiation can transfer their excited state energy to the
ground state of molecular oxygen to produce singlet oxygen species which are
highly cytotoxic. Hone et al
.
synthesized small AuNPs (2-4 nm diameter) stabi-
lized with a zinc(II) phthalocyanine derivative bearing a mercaptoundecyl group
attached to the surface of the nanoparticle through the formation of stable S-Au
bonds (Hone et al.
2002
) (Fig.
1
). AuNP-phthalocyanine conjugates are able to
generate singlet oxygen upon irradiation with enhanced quantum yields compared
to the free phthalocyanine. Camerin et al
.
also compared the
in vivo
efficacy of the
C11Pc molecule and the AuNP-C11Pc conjugates for the photodynamic therapy of
amelanotic melanoma cells (Camerin et al.
2010
) (Fig.
2
). C11Pc molecules and the
AuNP-C11Pc conjugates are not water-soluble and dispersed in a Cremophor EL
emulsion before injection. Biodistribution studies performed on C57 mice bearing
a subcutaneously transplanted amelanotic melanoma showed that cancer tissues are
more selectively targeted by the AuNP-C11Pc conjugates compared to the free
C
6
H
13
C
6
H
13
H
13
C
6
C
6
H
13
N
N
N
N
Zn
N
N
N
N
C
6
H
13
H
13
C
6
Fig. 1
1,4,8,11,15,18-
Hexaethyl-22-methyl-25-
(11-mercaptoundecyl)
phthalocyaninato zinc
H
3
C
(CH
2
)
9
HS
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