Chemistry Reference
In-Depth Information
8.5.1 Cellular Uptake and Phototoxicity of Transition Metal Polyazine Complexes
Recent studies of the interaction of platinum group polyazine complexes with cells
indicate that uptake of metal complexes by cells is greater with a compromised cel-
lular envelope. Dobrucki investigated [Ru(bpy)
3
]Cl
2
and [Ru(phen)]Cl
2
as confocal
microscopy imaging dyes of J144 mouse macrophages and normal human fi broblasts
(NFB).
80
The metal complexes were internalized by the cells with endocytosis.
Neither metal complex penetrated intact plasma membranes under dark conditions.
Visible light photolysis of cells with internalized metal complex resulted in redistri-
bution of the observed luminescence within the cell. Dobrucki suggests that Type
II photooxidation of the cell membrane compromises its integrity, allowing passage
of the metal complexes. Photoinduced cell death was noted for concentrations of
[Ru(phen)
3
]
2+
greater than 0.2 mM and irradiation with 490 nm light. Jimenez-
Hernandez, Orellana,
et al
. studied [(bpy)
2
Ru(ddz)]
2+
as a selective stain of nonvia-
ble rat hepatocytes.
81
A commonly used technique to image nonviable cells with
fl uorescence microscopy uses intercalation of the ethidium homodimer ion into
DNA, which greatly enhances ethidium emission. This provides red fl uorescent
imaging of the nonviable cells. The planar aromatic ddz ligand of [(bpy)
2
Ru(ddz)]
2+
readily intercalated DNA, also exhibiting a potent DNA light switch effect. Upon
passing through the leaky membrane of dead cells, [(bpy)
2
Ru(ddz)]
2+
is rapidly
bound by nuclear DNA to give an emissive label of nonviable cells.
A metal complex bound to an octa(arginine) tether [(arg)
8
] exhibited enhanced
cellular uptake and association with nuclear DNA.
82
Brunner and Barton studied
the cellular uptake of [(phen)(chrysi)Rh{dmb-(arg)
8
- DYE}](O
2
CCF
3
)
11
, where DYE
is a fl uorescein or thiazole orange fl uorescent tag. Uptake of the fl uorescein dye-
labelled metal complex was studied by confocal microscopy of metal complex bound
HeLa cells. Confocal microscopy images of cells incubated with 5
M showed that
the dye was rapidly incorporated into the nucleus. The authors suggest that the
design of the studied complexes could be adapted to build and understand the cel-
lular uptake mechanisms of other metal complexes.
Mononuclear ruthenium(II) and rhodium(III) polyazine complexes exhibit cel-
lular uptake mechanisms related to the lipophilicity of the metal complex. Puckett
and Barton studied the cellular uptake of a series of [(TL)
2
Ru(dppz)]Cl
2
complexes,
with TL = bpy, phen, Ph
2
phen, and 4 - carboxy - 4
µ
- bipyrindine (mcmb).
79
Uptake was observed using confocal microscopy with direct excitation of the Ru-
centred chromophore
′
- methyl - 2,2
′
ex
488
. The complex [(Ph
2
phen)Ru(dppz)]Cl
2
dis-
played the largest mean luminescence intensity inside the cell. The authors related
uptake to the octanol/water partition coeffi cient of the metal complexes, suggesting
a passive transport mechanism. Minimal emission was observed within the nucleus,
suggesting that transport across the nuclear envelop is retarded. Loganathan and
Morrison reported a similar enhanced cellular uptake with increasing lipophilicity
for
cis -
[(TL)
2
RhCl
2
]Cl as a function of TL methylation.
66
The authors report that
[(Me
4
phen)
2
RhCl
2
]Cl, at 55
λ
max
=
nm
400 nm light irradiation, caused a 20%
reduction in cell growth relative to dark controls. The authors were unable to assess
the mechanism of cell killing, but noted [(Me
4
phen)
2
RhCl
2
]Cl to be an effi cient
photobinder of DNA. Another DNA photobinding complex, [(phen)(dppz)RhCl
2
]Cl,
was reported to be phototoxic at 40
µ
M and with
>
M with 311 nm irradiation.
65
This complex was
µ
