Nanoparticles for Photodynamic Therapy Applications - Intracellular Delivery: Fundamentals and Applications - page 549

for the dye-TiO 2 particle than for chlorin e6 alone. The survival rate in the presence
of dye-TiO 2 gradually decreased with increasing dye concentration. In contrast, the
survival rate in the TiO 2 -free chlorin e6 system remained 100%, indicating that no
cytotoxic effect occured with TiO 2 alone in the dark as well as under visible light
irradiation. The measured photocytotoxicity would be caused by reactive oxygen
species, for example, singlet oxygen, superoxide, and hydroxy radical, generated
by the photoexcited dye-TiO 2 particles although the nature of reactive oxygen spe-
cies involved has not been specified. It was expected, however, that the positively
charged TiO 2 nanocrystals have higher affinity to tumor cells, which are more nega-
tively charged than normal cells (Miyasaka and Kijitori 2004 ).
Electroporation (Labanauskiene et al. 2007 ; Lambreva et al. 2004 ; Nolkrantz
et al. 2002 ; Underhill et al. 2003 ; Xu et al. 2007b ) is an important bioengineering
technique that has been used to deliver genes or anticancer drugs into the cytoplasm
through the micropores on the cell membrane produced through electric stimulation
and has been successfully utilized in photodynamic therapy. Xu et al. reported for
the first time that the combination of the electroporation and the conjugation of the
TiO 2 nanoparticles with the monoclonal antibody could improve the photokilling
selectivity and efficiency of photoexcited TiO 2 on cancer cells in PDT because the
conjugation of the TiO 2 nanoparticles with monoclonal antibodies could increase
the photokilling selectivity of TiO 2 nanoparticles to cancer cells and the electropora-
tion could accelerate the delivery speed of the TiO 2 nanoparticles to cancer cells.
They firstly conjugated TiO 2 nanoparticles with a specific antibody against the
carcinoembryonic antigen (Hefta et al. 1998 ) of human LoVo cancer cells.
Electroporation was used to improve the delivery of antibody-TiO 2 bioconjugates
into the cancer cells.
To obtain their nanoparticles, anti-carcinoembryonic antigen antibody was
mixed to fluorescein isothiocyanate-dimethylsulfoxide solution to obtain a FITC-
antibody solution which was added to a pH adjusted TiO 2 suspension (ratio of 800 mL
antibody solution with 1 mg TiO 2 nanoparticles). The selective binding of the
FITC-antibody-TiO 2 conjugate was compared between LoVo cancer cells and
TE353.sk normal cells. They observed that after the incubation in the culture
medium containing the FITC-antibody-TiO 2 conjugate for 30 min, LoVo cancer
cells clearly exhibit a green fluorescence light, in contrast TE353.sk normal cells
did not show any fluorescence, indicating that the FITC-antibody-TiO 2 conjugate
bind only to the LoVo cancer cells.
Using the combination of PDT and electroporation, 100% human LoVo cancer
cells were photodestroyed within 90 min, versus 39% for normal cells under ultra-
violet (UV) light (365 nm). Furthermore, the combination might be used to photo-
kill other types of cancer cells, by using other antibodies.
In 2010, Lopez et al. developed novel nanostructured TiO 2 and SiO 2 based bio-
catalysts, with 3-4 wt.% of Pt (Lopez et al. 2010b ). In fact, since the pioneer work
of Rosenberg in 1965, Pt complexes have been widely used in cancer therapy
(Rosenberg et al. 1965, 1969 ). From then on, numerous attempts to obtain new
platinum complexes with better therapeutic performances than cis-platin have been
made (Kovala-Demertzi et al. 2007 ; Marković et al. 2005 ).