Microwave-assisted synthesis of arene ruthenium(ii) complex as apoptosis inducer of A549 cells

Article abstract of DOI:10.1071/CH13269

An arene ruthenium(ii) complex coordinated with 2-(2-chlorophenyl)-1H- imidazo[4,5-f][1,10]phenanthroline, [(η6-C6H6)Ru(o-ClPIP)Cl]Cl (1), has been prepared by using microwave-assisted synthesis technology. The anti-tumour activity of this complex against

Full text of DOI:10.1071/CH13269

CSIRO PUBLISHING
Aust. J. Chem. 2013, 66, 1422–1427
Full Paper
http://dx.doi.org/10.1071/CH13269
Microwave-Assisted Synthesis of Arene Ruthenium(II)
Complex as Apoptosis Inducer of A549 Cells
A
A
A C
,
A
A
Qiong Wu, Jian Wu, Wen-Jie Mei,
Qi Wang, Zhao Zhang,
A
B C
,
A
A
Xiao-Hui Wu, Fen-Yong Sun,
Xiao-Ying Hu, and Yun-Yi Tao
Wei-Li Wu, Yan-Hua Chen,
A
A
A
School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou,
510006, China.
B
Department of Clinical Laboratory Medicine, Shanghai Tenth People’s
Hospital of Tongji University, Shanghai, 200072, China.
C
Corresponding authors. Email: wenjiemei@126.com; sunfenyong@263.net
An arene ruthenium(II) complex coordinated with 2-(2-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline,
[(Z6-C6H6)Ru(o-ClPIP)Cl]Cl (1), has been prepared by using microwave-assisted synthesis technology. The anti-tumour
activity of this complex against various tumour cells has been evaluated by MTT assay and the results show that complex 1
exhibits selective inhibitory activity against the growth of human lung adenocarcinoma A549 cells with IC50 ¼ 31.58 mM.
Further studies by flow cytometric analysis showed that apoptosis of A549 cells was observed when dealt with complex 1.
Furthermore, complex 1 exhibits excellent binding affinity with DNA molecules which was confirmed by spectroscopy
methods, as well viscosity and melting point experiments. As a result, the conformation of DNA molecules was disturbed
by complex 1.
Manuscript received: 28 May 2013.
Manuscript accepted: 25 July 2013.
Published online: 13 September 2013.
Introduction
research group found that imidazole phenanthrolines them-
selves displayed excellent inhibitory activity by induced apo-
ptosis of lung cancer A549 cells via the NF-kB signalling
pathway.[25] Studies in our research group suggest that an arene
RuII complex coordinated with imidazole phenanthroline shows
promising anti-tumour activity by inducing cell cycle arrest at
the S-phase.[26] However, the anti-tumour mechanism and the
DNA-binding behaviour of these kinds of arene complexes is
still not clear, and it is still very important to design novel
candidates with high activity and selectivity.
In this paper, we report the microwave synthesis of an arene
RuII complex coordinated by 2-(2-chlorophenyl)-1H-imidazo
[4,5-f][1,10]phenanthroline, [(Z6-C6H6)Ru(o-ClPIP)Cl]Cl (1),
as shown in Scheme 1. We found that complex 1 could
selectively inhibit the growth of A549 cells with similar levels
to cisplatin. Apoptosis of A549 cells induced by complex 1 was
observed by flow cytometric analysis. The DNA-binding prop-
erties of complex 1 with calf thymus deoxyribonucleic acid
(CT-DNA) was investigated by spectroscopic methods and the
DNA cleavage ability of complex 1 was evaluated through gel
Arene RuII complexes have long been studied as promising anti-
tumour candidates, because of their low toxicity to human
normal cells but high inhibitory activity against various tumour
cells.[1–5] In recent years, several arene ruthenium(II) complexes
have been designed,[6–8] and their in vivo and in vitro anti-
tumour activity,[9–11] as well as their mechanism to inhibit
the growth of tumour cells has been investigated. Dyson and
co-workers reported that (Z6-p-MeC6H4Pri)Ru(p-pta)Cl2
(RAPTA-C), a classic arene RuII complex, exhibited prominent
anti-tumour activity by inhibiting cell cycle progression at the
G2/M phase and inducing apoptosis of tumour cells.[12,13] Sadler
et al. also indicated that arene RuII complexes coordinated by
phenanthroline lighands could suppress the growth of various
tumour cells at low initial concentration by intercalating into the
base-pair of duplex DNA,[14–16] and the presence of the arene
ligand played a key role for binding affinity of these RuII
complexes with DNA molecules.[17,18]
Furthermore, a large body of evidence suggests that Ru
complexes coordinated with phenanthroimidazole derivatives,
a large aromatic planar ligand, usually exhibit high anti-tumour
activity by inducing apoptosis of tumour cells.[19–22] Ji and
co-workers showed that RuII polypyridyl complexes bearing
1H-imidazo[4,5-f][1,10]phenanthroline analogues, such as
[Ru(bpy)2(bfipH)]2þ and [Ru(phen)2(bfipH)]2þ (bpy ¼ 2,20-
ꢀ·Clꢁ
Cl
N
NH
Ru
N
N
bipyridine;
phen ¼ 1,10-phenanthroline;
bfipH ¼ 2-
Cl
(benzofuran-2-yl)imidazo[4,5-f][1,10]phenanthroline), showed
high binding affintiy to DNA, which was attributed to the ideal
planarity of the intercalating ligand.[23,24] More recently, our
Scheme 1. The molecular structure of arene RuII complex 1.
Journal compilation Ó CSIRO 2013
www.publish.csiro.au/journals/ajc

A549 Cell Apoptosis Induced by Arene RuII Complex
1423
electrophoresis experiments. Results show that complex 1
intercalates to CT-DNA, inducing DNA damage resulting in
apoptosis of A549 cells.
(100 units/mL), and streptomycin (50 units/mL) at 378C in a CO2
incubator (95 % relative humidity, 5 % CO2).
MTT Assay
Experimental
Cell viability was determined by measuring the ability of cells to
transform 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (MTT) to a purple formazan dye.[30] Cells were seeded
in 96-well tissue culture plates for 24 h. The cells were then
incubated with the tested compounds at different concentrations
for different periods of time. After incubation, 20 mL of MTT
solution (5 mg mLꢀ1 in phosphate buffered saline, PBS) was
added to each well, followed by incubation for a further 5 h. The
medium was aspirated and replaced with 150 mL/well of DMSO
to dissolve the formazan salt formed. The colour intensity of the
formazan solution, which reflects the cell growth condition, was
measured at 570 nm using a microplate spectrophotometer
(SpectroAmaxTM 250).
Chemicals
Ruthenium(III) chloride hydrate was obtained from Mitsuwa Che-
micals. 1,10-Phenanthroline monohydrate, 1,3-cyclohexadiene,
and 2-chlorobenzaldehyde were purchased from Aldrich. All
chemicals including solvents were obtained from commercial
vendors and used as received. Calf thymus DNA (CT-DNA) and
pBR-322 DNA was purchased from Guangzhou Ruizhen Bio-
technology Co. 1,10-Phenanthroline-5,6-dione was prepared by
a similar method reported in the literature.[27] [(Z6-C6H6)
RuCl2]2 was prepared according to literature.[6] All aqueous
solutions were prepared with doubly distilled water. The Tris-
HCl buffer was made from tris(hydroxymethyl)aminomethane,
Tris (617 mg) and NaCl (292.5 mg), adjusted to pH 7.2 by HCl
(0.1 M); this buffer was used for ultraviolet (UV) titration,
fluorescence quenching, thermal denaturation, circular
dichroism (CD) spectra, and viscosity measurements.
Flow Cytometric Analysis
The apoptosis rate was analysed by flow cytometry as previ-
ously described.[31] Treated or untreated cells were trypsinised,
washed with PBS, and fixed with 75 % ethanol overnight at
ꢀ208C. The fixed cells were washed with PBS and stained with
propidium iodide (PI) for 4 h in darkness. The stained cells were
analysed with an Epics XL-MCL flow cytometer (Beckman
Coulter, Miami, FL).
Synthesis of 2-(2-Chlorophenyl)-1H-imidazo[4,5f][1,10]
phenanthroline (o-ClPIP)
The ligand 2-(2-chlorophenyl)-1H-imidazo[4,5f][1,10] phe-
nanthroline (o-ClPIP) was prepared by a similar method as the
literatures with some modifications.[28] 1,10-Phenanthroline-
5,6-dione (347 mg, 1.6 mmol), 2-chlorobenzaldehyde (224 mg,
1.6 mmol), and ammonium acetate (2.53 g) was dissolved in
20 mL acetic acid and the resulting solution was heated at reflux
at 1108C for 4 h. Then 20 mL of water was added and the pH
value was adjusted to 7.0 at room temperature. A yellow
precipitate was obtained after filtration, before drying
undervaccum. The products were purified silica gel chroma-
tography using ethanol as eluent to give the title compound
(348 mg, 65.9 %).
Results and Discussion
Synthesis and Characterisation
The use of microwave reactors are becoming a rapidly
expanding area in synthetic chemistry in both organic and
inorganic synthesis.[32] The technique potentially reduces
overall processing time, while enhancing yield and product
purity over traditional synthesis methods, especially in the
synthesis of Ru complexes which typically require many hours
of heating at reflux in high-boiling solvents to affect a reaction.
Arene RuII complex 1 was prepared from [(Z6-C6H6)RuCl2]2
and o-ClPIP at 608C under microwave irradiation for 30 min in a
Pyrex vessel, in a yield of 90.7 %, which is markedly higher than
the methof from conventional synthesis.[33]
Synthesis of [(C6H6)Ru(o-ClPIP)Cl]Cl (1)
The arene ruthenium(II) complex 1 was prepared according to a
literature procedure[29] but with some modifications. A mixture
of [(Z6-C6H6)RuCl2]2 (75 mg, 0.15 mmol) and o-ClPIP(99.3 mg,
0.3 mmol) in dichloromethane (20 mL) was heated at reflux at
608C in a sealed reaction vessel in a microwave reactor (Anton
Paar Monowave 3000, Graz, Austria) for 30 min. A yellow
precipitate was obtained after rotary evaporation, which was
purified by recrystallisation from distilled water to give the title
compound (105 mg, 90.7 %). 1H NMR (500 MHz, [D6]DMSO)
d 10.00 (d, J ¼ 4.6 Hz, 2H), 9.35 (s, 2H), 8.20 (dd,
J ¼ 8.0, 5.4 Hz, 2H), 7.99 (dd, J ¼ 7.4, 1.6 Hz, 1H), 7.72 (d, 1H),
7.58 (dt, J ¼ 16.1, 7.3 Hz, 2H), 6.35 (s, 6H). 13C NMR
(126 MHz, [D6]DMSO) d 154.67, 150.99, 143.90, 133.13,
132.72, 132.52, 132.15, 130.93, 129.68, 127.98, 126.63, 87.32.
m/z (ESI) 547.1 [M-Cl]þ.
The electrospray ionisation mass spectrum (ESI-MS) of
complex 1 exhibited a peak at m/e 547.1 (100 %) ascribed to
[M-Cl]þ, which was in agreement with the theoretical value.
1
The peak at d 6.33 ppm (s, 6H) in the H NMR spectrum was
assigned to resonance of the corresponding protons H-1 in the
C6H6 ring; the peaks at d 10.00 (d, J ¼ 5.0 Hz, 2H), 9.35 (s, 2H),
and 8.20 (dd, J ¼ 8.0, 5.0 Hz, 2H) ppm were ascribed to protons
in the phenanthroline ring o-ClPIP of H-2, H-4, and H-3,
respectively (Fig. 1a). This was confirmed by the 1H-1H COSY
spectrum of complex 1 (Fig. 1b) which shows H-3 coupled with
H-2 and H-4, and H-6, H-7, H-8, and H-9 in the benzene ring of
phenanthroline coupled with each other.
Biological Studies
Cell Lines and Cell Culture
Complex 1 was evaluated in a comparative in vitro MTT cell
viability assay with three tumorigenic cell lines, human lung
adenocarcinoma A549, human hepatocellular carcinoma
SMMC-7721, and colorectal adenocarcinoma SW620, versus
normal cells (human immortalised keratinocyte HaCaT cells).
The IC50 values for complex 1 and the positive control cisplatin
are depicted in Table 1. These data indicate that 1 selectively
inhibits A549 cells at similar levels to cisplatin, whereas the
activity is much lower against SMMC-7721 and SW620 cells.
Human cancer cell lines, including human lung adenocarcinoma
A549, human hepatocellular carcinoma SMMC-7721, colorec-
tal adenocarcinoma SW620, and human immortalised kerati-
nocyte HaCaT cell lines were purchased from American Type
Culture Collection (ATCC, Manassas, VA). All cell lines were
maintained in either Roswell Park Memorial Institute 1640
(RPMI-1640) or Dulbecco’s Modified Eagle Medium (DMEM)
media supplemented with fetal bovine serum (10 %), penicillin

1424
Q. Wu et al.
1
(a)
2
9
3
8
7
6
4
3
(b)
6.0
6.5
7.0
7.5
8.0
8.5
1
2
4
5
Cl
3
1
1
6
N
2
4
NH
2
Cl
Ru
5
7
6
N
NH
N
N
9
8
Ru
Cl
7
N
N
9
8
Cl
3
9
6
87
4
9.0
9.8
9.2
8.6
f1 [ppm]
8.0
9.5
10.0
9.7
9.1
8.5
7.9
7.3
6.7
10.0
9.4
8.8
8.2
7.6
7.0
6.4
f1 [ppm]
f2 [ppm]
Fig. 1. (a) 1H NMR spectra of complex 1. (b) 1H-1H COSY of complex 1.
attributed to the IL (intraligand charge transfer) absorption,
and an absorption appeared at 295 nm which was attributed to
LMCT (ligand to metal charge transfer) absorption. Upon
the addition of CT-DNA, the absorption of IL and electronic
spectra undergoapparenthypochromism, and the hypochromism
calculated for IL absorption and LMCT absorption was ,16 and
12 %, respectively.
The intrinsic binding constant (K) was calculated according
to the decay of the IL absorption using the Stern–Volmer
equation:[34]
Table 1. IC50 values of complex 1 on tumorigenic cell lines after 72 h
of incubation, determined using the MTT assay
Complexes
IC50 [mM]
A549
SMMC7721
SW620
HaCaT
1
31.58
16.54
.100
2.92
.100
.100
Cisplatin
5.74
7.48
Arene ruthenium complex 1 exhibited low toxicity towards
normal human HaCaT cells compared to cisplatin, which shows
that 1 is a selective inhibitor for lung adenocarcinoma with low
toxicity against normal human cells.
ðea ꢀ ef Þ=ðeb ꢀ ef Þ ¼ ½b ꢀ ðb2 ꢀ 2K2Ct½DNAꢁ=SÞꢁ1=2=2KCt
b ¼ 1 þ KCt þ K½DNAꢁ=2S
At this point it was unclear what the anti-tumour mechanism
of arene RuII complexes was. To investigate the anti-tumour
mechanism of complex 1 further, A549 cells were exposed to
different concentrations of 1 (0, 50, 75, and 100 mM) for 24 h and
examined by flow cytometric (FCM) analysis. Results show a
prominent increase in cell apoptosis at 24 h in Fig. 2. Upon
increasing the concentration of complex 1, the level of apoptosis
rises markedly, reaching 39.88 % for the 100 mM experiment,
approximately four-fold higher than that of the control
(10.86 %), indicating that the arene RuII complex might be
inhibiting the growth of A549 cells by induced apoptosis.
The intrinsic binding constant K calculated for complex 1 is
,2.47 ꢂ 105 Mꢀ1, which shows that complex 1 exhibits a
certain DNA-binding affinity.
Fluorescence Quenching
Owing to the low fluorescence of complex 1 in Tris-HCl
buffer (pH ¼ 7.2), fluorescence quenching of ethidium bromide
(EB) and DNA was carried out to further study the DNA-binding
behaviour of complex 1. Fluorescence quenching can be used to
study the affinity of a complex to DNA, not just its binding
mode,[35] and the results are illustrated in Fig. 4.
DNA-Binding Properties of Arene Ruthenium(II) Complexes
Electronic Spectra
Electronic absorption spectroscopy is one of the most com-
mon methods to study the interaction of ruthenium complexes
with DNA. In general, ruthenium complexes have characteristic
spectroscopic properties, which undergo hypochromism and red
shift in the presence of DNA; the degree of change is usually
proportional to the binding strength. Electronic spectra were
recorded to clarify the interaction of complexes 1 with
CT-DNA, as shown in Fig. 3.
A strong fluorescence was observed in the range of
550–690 nm at room temperature, the maxima was at
,600 nm when excited at 530 nm. Upon increasing the con-
centration of complex 1, the emission intensity of the EB-DNA
system deceased dramatically, resulting from the replacement
of EB which is a classical DNA intercalator.[36,37] According to
these results we conclude that complex 1 competitively binds
with DNA over EB, which is in agreement with the electronic
spectra, indicating that complex 1 interacts with DNA in an
intercalative mode.
As shown in Fig. 3, there was a characteristic absorption at
271 nm in the electronic spectra of complex 1 which was

A549 Cell Apoptosis Induced by Arene RuII Complex
1425
0.6
0.5
0.4
0.3
0.2
0.1
0
(a)
1.0
0.8
0.6
0.4
0.2
0
50 µM
Control
17.01 %
10.86 %
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
[DNA] ꢂ 1 ꢃ 10ꢁ6 M
100
101
102
103
104100
101
102
103
104
FL1-H
FL1-H
100
µ
M
75 µM
250
300
350
400
450
500
Wavelength [nm]
39.88 %
29.21 %
Fig. 3. Electronic spectra of 1 in Tris-HCl buffer (pH ¼ 7.2) in the absence
and presence of calf thymus DNA. [Ru] ¼ 10.0 mM.
100
(b)
101
102
103
104100
101
102
103
104
0.12
250
0.10
0.08
FL1-H
FL1-H
200
0.06
40
30
20
10
0
0.04
0.02
150
0
2
4
6
8
10 12 14 16
[DNA] ꢂ 1 ꢃ 10ꢁ6M
100
50
0
570
600
630
660
690
0
50
75
100
Wavelength [nm]
Concentration [µM]
Fig. 4. Emission spectra of EB-DNA in Tris-HCl buffer (pH ¼ 7.2) in the
absence and presence of complex 1. [EB] ¼ 16 mM, [DNA] ¼ 100 mM.
Arrow shows the emission intensity changes upon increasing concentration
of 1.
Fig. 2. (a) FCM analysis of the apoptosis of A549 cells treated with
complex 1 after 24 h. The effect of complex 1 (50, 75, and 100 mM) on A549
cell apoptosis was determined by flow cytometry. Untreated (control) cells
or cells treated for 24 h were harvested, fixed, stained with Annexin V/PI,
and assessed for cell apoptosis distribution by flow cytometric analysis.
(b) Percentages of apoptotic cells were measured by the annexin V/PI flow
cytometry analysis, as described in the Experimental section. The y-axis
plots the sum of early and late apoptotic cells as the mean ꢃ standard
deviation of three independent experiments.
10
5
Circular Dichroism
0
The interaction of complex 1 with CT-DNA was further
studied by circular dichroism.[8] By observing the change in CD
signal of CT-DNA upon addition of complex 1, conformational
changes of DNA caused by the binding of complex 1 can be
elucidated. These results are shown in Fig. 5.
There is a positive CD signal apparent in the range of
230–290 nm for CT-DNA, with the maxima at 280 nm. When
complex 1 was added to the solutions, the positive CD signal of
CT-DNA decreased distinctly, which indicated the conforma-
tion of double-stranded DNA was disturbed by complex 1. On
the basis of the above analysis, complex 1 disturbs the DNA
conformation after binding with DNA, which might lead to a
series of changes in the biological process.
ꢁ5
ꢁ10
ꢁ15
240
260
280
300
320
Wavelength [nm]
Fig. 5. The change of CD spectra of CT-DNA with the increasing
concentration of complex 1. [DNA] ¼ 100 mM, [Ru] ¼ 0, 2, 4 mM.

1426
Q. Wu et al.
1.25
1.20
1.15
1.10
1.05
1.00
1.5
0
ꢁ1.5
ꢁ3.0
ꢁ4.5
0
0.02
0.04
0.06
0.08
0.10
30
40
50
60
70
80
90
Temperature [ꢄC]
[Ru]/[DNA]
Fig. 6. Effects of complex 1 (’) and [Ru(bpy)3]þ (£) on the relative
viscosity of CT-DNA.
Fig. 7. Typical CD melting curves of CT-DNA without (—) or with 1
(- - -) in Tris-HCl buffer (pH ¼ 7.2). The CD signal was recorded with a
positive band at 280 nm. [DNA] ¼ 100 mM; [Ru] ¼ 10 mM.
Viscosity Experiments
The relative viscosity of DNA increases with the addition
of metal complexes that bind by intercalation. Viscosity
measurements have proven to be an important method to
study the mode of binding of compounds to DNA. In general,
intercalation of a compound into DNA is known to cause an
observable increase in the viscosity of a DNA solution due to
an increase in the distance of base pairs at the intercalation
site.[38] Viscosity changes were measured using CT-DNA
with increasing concentrations of the complex 1, as shown
in Fig. 6.
(a)
(b)
Form I
Form II
0
6
12
24
0
6
12
Ru [µM]
24
Ru [µM]
The effects of complex
1
versus [Ru(bpy)3]þ on
Fig. 8. Photocleavage of plasmid pBR-322 DNA in the absence and
presence of complex 1 without light irradiation (a) and with light irradiation
at 365 nm for 30 min (b).
the relative viscosity of rod-like DNA are shown in
Fig. 6. It is well known that [Ru(bpy)3]þ interacts with
DNA in a classical electronic effect.[39] On increasing the
concentration of complex 1, the relative viscosity of the DNA
increased steadily compared to [Ru(bpy)3]þ. Thissuggests
that complex 1 inserts into the base-pairs of CT-DNA via
an intercalative mode, which is in agreement with the
spectroscopic studies.
Photocleavage of pBR-322 DNA by Arene Ruthenium(II)
Complex 1
The cleavage activity on plasmid DNA induced by ruthenium(II)
complexes was tested by agarose gel electrophoresis. Circular
plasmid DNA in the intact supercoiled form moves at the front in
electrophoresis; if breakage occurs on one strand (nicked), the
supercoiled DNA migrates after the circular form.[43] The
photocleavage of plasmid pBR-322 DNA by complex 1 was
evaluated by gel electrophoresis, as shown in Fig. 8.
Gel electrophoresis was carried out for 1 on pBR-322 DNA
after incubation, with and without light irradiation at 365 nm for
30 min. As shown in Fig. 8a, little DNA cleavage was observed
for the control (0) and for the sample containing complex 1
(6, 12, and 24 mM) without light irradiation. While under light
irradiation, the amount of supercoiled conformation (Form I) of
plasmid pBR-322 DNA diminishes gradually with increasing
concentrations of complex 1, whereas the nicked formation
(Form II) of DNA increases. These results indicate that complex
1 inhibits the growth of tumour cells by disturbing the confor-
mation of DNA molecules but not by direct DNA damage,
which may be the reason for low toxicity to human normal cells.
Melting Point Experiments
Melting point (Tm) studies were undertaken to further exam-
ine the conformation of CT-DNA after binding with complex 1.
In general, double-stranded DNA will gradually dissociate to
single strands following an increase in temperature, which can
be followed by examining the CD signal decrease at 280 nm.[40]
A large change in the Tm of DNA is an indication of a strong
interaction between a complex and DNA. The interaction of
complex 1 with CT-DNA was characterised by measuring the
effects on melting temperature of DNA, and the results are
shown in Fig. 7.
The melting point (Tm) for CT-DNA in the absence and
presence of complex 1 was determined by CD spectra to be
,80.1 ꢃ 0.12 and 84.9 ꢃ 0.158C (DTm ¼ 4.88C), respectively.
These data are comparable to that observed for [Ru(bpy)2
(dpoq)](ClO4)2ꢄH2O (DTm ¼ 4.08C) and [Ru(phen)2(dpoq)]
(ClO4)2ꢄH2O (DTm ¼ 5.88C) (dpoq ¼ dipyrido[1,2,5]oxadiazolo
[3,4-b]quinoxaline),[41] indicating that complex 1 stabilises the
conformation of CT-DNA by intercalating into the base pairs of
the double helix of DNA.[42]
Conclusion
In summary, arene RuII complex 1 was synthesised using
microwave-assisted technology, in a high yield of 90.7 %.

A549 Cell Apoptosis Induced by Arene RuII Complex
1427
According to MTT results, complex 1 exhibited selective inhi-
bition to A549 cells at similar levels to cisplatin. Flow cytometry
indicated that arene RuII complex 1 could induce apoptosis of
A549 cells. The interaction of complex 1 with CT-DNA was
studied by spectroscopy, viscosity, and melting point experi-
ments and the results suggest that complex 1 interacts with
CT-DNA by intercalation, with an intrinsic binding constant of
2.47 ꢂ 105 Mꢀ1. Furthermore, studies by gel electrophoresis
indicate that complex 1 cleaves plasmid pBR-322 DNA from the
supercoiled form to the nicked form effectively under the irra-
diation of light, which shows potential utility in chemotherapy.
Taken together, these results suggest that arene RuII complex
interacts with DNA causing induction of A549 cell apoptosis.
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Acknowledgements
This work was supported by the Natural Science Foundation of China and
Guangdong Province, Key Project of Science and Technology Department
of Guangdong Province, the Science and Technology Planning Project of
Guangdong Province and the Science and Technology Planning Project of
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