Biomedical Engineering Reference
In-Depth Information
avoid photobleaching. On the contrary, the mesoporous silica shell allowed the
diffusion of
1
O
2
outside of the nanoparticle. TEM images revealed a monomodal
particle size distribution around 57 nm for mesoporous core-shell nanoparticles and
37 nm for silica cores. Disodium 9,10-anthracenediyl-bis-(methylene)dimalonic
acid (ABMD) was used to chemically check the capacity of such material to pro-
duce
1
O
2
. A significant decrease of ABMD absorption for SiO
2
@HP and HP alone
was observed, but for the same amount of HP, the decrease was more important for
SiO
2
@HP or FITC@SiO
2
@HP than for HP alone, due to a higher stability of PS
covalently linked in a silica shell. Moreover, the FITC inside the non-porous silica
shell was well protected from the damage by
1
O
2
(no photobleaching). Finally, the
imaging capability was demonstrated by cell imaging on HO-8910 PM cells.
Confocal microscopy on such cells showed that most of the nanoparticles were
localized in the membrane of the cell and a few inside the cell.
Hsiao and collaborators reported the synthesis of a multifunctional nanomate-
rial conjugating a functionalized iridium complex with a Fe
3
O
4
/SiO
2
core/shell
nanocomposite (Lai et al.
2008
). The magnetic core provides capability for MRI.
The silica shell allows the embedment of the PS, with sufficient space for oxygen
diffusion. A third row transition metal (Ir(III)) complex was chosen as the PS to
serve both as a photosensitizer and as a luminescent moiety. A hydrophilic irid-
ium (III) complex (Fig.
29
) was developed to generate a good affinity with the
silica shell.
The size of the nanoparticles was determined by TEM, 55 ± 5 nm for Fe
3
O
4
/
SiO
2
(Ir) nanoparticles compared to 12 ± 1 nm for Fe
3
O
4
. Upon aeration, both emis-
sion intensity and observed lifetime decreased drastically suggesting an O
2
quench-
ing process presumably resulting in
1
O
2
production. PDT experiments were
performed on HeLa cells. The cellular uptake and imaging ability were confirmed
by MRI revealing that the cellular-uptake was dose-responsive and that the uptake
could be imaged by MRI at low concentration (6.25 mg mL
−1
). The cytotoxicity of
the particles towards HeLa cells was demonstrated upon irradiation. Evidence of
1
O
2
-induced apoptosis was found. This is the first example of a multifunctional
N
Ir
N
N
N
N
OEt
N
EtO
Si
O
EtO
O
Fig. 29
Ir(III) complex (Reproduced by permission of The Royal Society of Chemistry)
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