Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles

Article abstract of DOI:10.1021/jacs.8b04929

Light-emitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the chemical and biological sciences. Herein, we report the coordination-driven self-assembly of two highly emissive platinum(II) supramolecular trian

Full text of DOI:10.1021/jacs.8b04929

Subscriber access provided by UNIVERSITY OF TOLEDO LIBRARIES
Article
Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles
Jiong Zhou, Yuzhen Zhang, Guocan Yu, Matthew R Crawley, Cressa Ria Palencia Fulong, Alan
Eric Friedman, Sanghamitra Sengupta, Jifu Sun, Qing Li, Feihe Huang, and Timothy R. Cook
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b04929 • Publication Date (Web): 22 May 2018
Downloaded from http://pubs.acs.org on May 22, 2018
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 8
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Highly Emissive SelfꢀAssembled BODIPYꢀPlatinum Supramolecular
Triangles
†,‡
‡
,†,§
‡
‡
Jiong Zhou, Yuzhen Zhang, Guocan Yu,* Matthew R. Crawley, Cressa Ria P. Fulong, Alan E.
ǁ
‡
†
†
,†
,‡
Friedman, Sanghamitra Sengupta, Jifu Sun, Qing Li, Feihe Huang,* and Timothy R. Cook*
†
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
State Key Laboratory of Chemical Engineering, Center for Chemistry of HighꢀPerformance and Novel Materials,
Department of Chemistry, Zhejiang University, Hangzhou 310027, P. R. China
‡
Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260, United
States
§
Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering,
National Institutes of Health, Bethesda, Maryland 20892, United States
ǁ
Department of Materials Design and Innovation, University at Buffalo, The State University of New York, Buffalo, New
York 14260, United States
Email addresses: guocanyu@zju.edu.cn; fhuang@zju.edu.cn; trcook@buffalo.edu
ABSTRACT: Lightꢀemitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the
chemical and biological sciences. Herein, we report the coordinationꢀdriven selfꢀassembly of two highly emissive platinum(II)
supramolecular triangles (1 and 2) containing BODIPYꢀbased bridging ligands. The metallacycles exhibit favorable anticancer
activities against HeLa cells (IC50 of 6.41 ꢀM and 2.11 ꢀM). The characteristic ~570 nm fluorescence of the BODIPY moieties in
the metallacycles permits their intracellular visualization using confocal microscopy. Additionally, the BODIPY fluorophore is an
excellent photodynamic agent, making the metallacycles as ideal therapeutics for photodynamic therapy (PDT) and chemotherapy.
In vitro studies demonstrate that the combination indexes against HeLa cells are 0.56 and 0.48 for 1 and 2, respectively, confirming
their synergistic anticancer effect. More importantly, these SCCs also exhibit superior anticancer efficacy towards
cisplatinꢀresistant A2780cis cell line by combining PDT and chemotherapy, showing promise in overcoming drug resistance. This
study exploits a multiꢀcomponent approach to selfꢀassembled metallacages that enables design of effective theranostic agents
wherein the platinum acceptors are toxic chemotherapeutics and the BODIPY donors are imaging probes and photosensitizers.
Since each piece may be independently tuned, i.e. Pt(II) polypyridyl fragment swapped for Pt(II) phosphine, the activity may be
optimized without a total redesign of the system.
used in photodynamic therapy, bioimaging, chemosensors, and
light harvesting. Collectively, BODIPY dyes exhibit
INTRODUCTION
6
numerous favorable properties, including high fluorescence
quantum yields, large molar absorption coefficients, easy
functionalization, and excellent photostability. Although
tetraphenylethene (TPE) and other fluorescent molecules have
been used as imaging probes in SCCs, highly emissive SCCs
based on BODIPYꢀcontaining donors are rare and
Coordinationꢀdriven selfꢀassembly is a powerful synthetic
methodology providing access to discrete supramolecular
coordination complexes (SCCs) with wellꢀdefined shapes and1
sizes by the spontaneous formation of metal–ligand bonds.
Owing to the wide range of metals and ligands that are
compatible with this strategy, an expansive library of
structurally complex twoꢀdimensional (2D) metallacycles and
threeꢀdimensional (3D) metallacages has emerged over the
7
Pt(II)ꢀBODIPY SCCs have not been explored as theranostic
8
agents.
Herein, we report the coordinationꢀdriven
selfꢀassembly of two novel Pt(II) supramolecular triangles
containing a pyridylꢀfunctionalized BODIPY ligand. The
presence of Pt(II) ions serving as the metal nodes of triangles
provide a mechanism for anticancer activity, resulting in
biological activity. The BODIPY cores within triangles enable
their transport within cancer cells to be visualized by confocal
laser scanning microscopy. Moreover, the BODIPY ligands
also form the basis for use as a photosensitizer for
photodynamic therapy (PDT). The combination of PDT and
chemotherapy greatly enhances anticancer efficacy through a
synergistic therapeutic effect. More interestingly, these SCCs
exhibited high cytotoxicity against drug resistant cancer cells
due to their dual mechanism of action (PDT and
chemotherapy), thereby obviating the ubiqutous problem of
2
past few decades. These metallosupramolecular architectures
are of particular interest not only for their aesthetic properties
but also because of their extensive applications in catalysts,
sensors, supramolecular polymers, amphiphilic selfꢀassembly,
3
host–guest chemistry, and biomedicines. Due to the
anticancer activity of organometallic platinum (Pt) complexes
and the large number of metallacycles and cages constructed
from Pt(II) nodes, biologically active SCCs have emerged in
4
recent years. Unlike mononuclear clinical drugs, such as
cisplatin, imaging capability can also be integrated into these
SCC platforms by simply choosing fluorescent ligands as
5
components of the building blocks.
Boron dipyrromethene (BODIPY) dyes have been widely
1
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 8
Scheme 1. (Left) Structures of 3−5 and SelfꢀAssembled Triangular Metallacycles 1 and 2. (Right) Cartoon Illustration of the
Cellular Uptake of Nanoparticles Prepared from 1 and 2.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
drug resistance.
RESULTS AND DISCUSSION
Preparation and Characterization of Triangular
Metallacycles. The BODIPY ligand 3 was synthesized by a
Sonogashira coupling following iodonation of the dye core
(Scheme S1). A single crystal of 3 suitable for Xꢀray
diffraction was obtained by slow diffusion of nꢀhexane into
the dichloromethane solution at room temperature (Figure 1).
In the BODIPY core, the central sixꢀmembered ring is almost
coplanar with the adjacent fiveꢀmembered pyrrole rings with
the maximum deviations of all nonꢀhydrogen atoms from the
mean plane of 0.079 Å, indicating strong πꢀelectron
9
delocalization within the indacene plane. The phenyl ring at
the mesoꢀposition is twisted by 79.61° from the BODIPY
plane. The average bond lengths for B–N and B–F and the
N–B–N and F–B–F angles are 1.555(2), 1.387(2) Å, 106.8(1),
1
09.7(1)°, respectively. The pyridyl rings are also twisted
away from the indacene plane. The dihedral angle between the
pyridine rings and the indacene plane is 15.66°. See Table S1
for complete crystallographic details. The nearly linear
directional nature of 3 makes it an excellent buliding block for
SCCs. Treatment of Pt(II) acceptors 4 or 5 with 3 in a 1:1 ratio
in CH Cl /DMA at 60 °C for 24 h led to the formation of
Figure 1. Crystal structure of 3: (a) side view; (b) top view.
Hydrogen atoms are omitted for clarity. Thermal ellipsoid is
drawn at 50% probability level. CCDC Number 1569252.
The formation of two triangular metallacycles was
1
supported by multinuclear NMR spectroscopy ( H NMR and
2
2
31
1
selfꢀassembled [3+3] triangular metallacycles
respectively (Scheme 1).
1
or 2,
P{ H} NMR), electrospray ionization mass spectroscopy
(ESIꢀMS), 2D diffusionꢀordered spectroscopy (DOSY),
UV–vis spectroscopy, and fluorescence spectroscopy. In the
1
H NMR spectrum of 1, the peak corresponding to pyridyl
proton H (from 8.54 to 8.57 ppm) displayed a downfield shift
3a
as compared to that of the free ligand 3. The peaks for
bipyridyl protons H4a (from 8.65 to 8.87 ppm) and H4b (from
8
.34 to 8.41 ppm) showed downfield shifts relative to those of
Pt(II) acceptor 4 (Figure 2b), consistent with coordination of
8b
1
the N atoms to Pt centers. Similarly, in the H NMR
spectrum of 2, the peak for pyridyl proton H3a (from 8.54 to
8
.62 ppm) displayed a downfield shift compared with that of
2
ACS Paragon Plus Environment

Page 3 of 8
Journal of the American Chemical Society
3
1
1
free ligand 3 (Figure 2d). Additionally, the P{ H} NMR
spectrum of 2 exhibited a lone singlet at –3.04 ppm, consistent
with a single phosphorus environment (Figure 2g). This peak
was shifted upfield relative to that of Pt(II) acceptor 5 by 7.98
ppm. The wellꢀdefined signals in both the H NMR and P{ H}
NMR spectra supported the formation of discrete, highly
symmetric species.
1
2
3
4
5
6
7
8
9
1
31
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 3. Experimental (red) and calculated (blue) ESIꢀMS
spectra of (a) 1 [M − 5OTf] and (b) 2 [M − 5OTf] .
5+
5+
The fluorescence properties of the BODIPY ligand 3 and
triangular metallacycles 1 and 2 were also studied in a range
of solvents (Figures S21b, S22b, and S23b). Metallacycles 1
and 2 were highly fluorescent when excited at 365 nm and
showed an emission peak at ~577 nm, originating from the
BODIPY cores (Figure 4). Both triangles showed small shifts
in their emission maxima depending on the solvent used
(Figure S24). Using Rhodamine B (Φ = 31% in water) as a
F
10
standard, the quantum yields (Φ ) of ligand 3 and triangular
F
metallacycles 1 and 2 were determined in different solvents
(
Table S2). Although some variation was observed, we note
that in all cases the emission quantum yields remained high. It
has been observed that if the Pt(II) nodes are too close to the
BODIPY cores, emission may be quenched, presumably due
to the heavyꢀmetal effect that populates dark triplet states.
Introducing ethynyl spacers to move the Pt(II) centers further
away has been observed to limit the attenuation of quantum
1
31
1
Figure 2. (a−e) H and (f,g) P{ H} NMR spectra (acetonitrileꢀd ,
3
293 K) of free building blocks 4 (a), 3 (c), and 5 (e,f) and
triangular metallacycles 1 (b) and 2 (d,g).
8a
yield.
Electrospray ionization mass spectrometry (ESIꢀMS)
provided strong evidence for the stoichiometry of formation of
triangular metallacycles 1 and 2. In the mass spectrum of 1,
three peaks were found that were consistent with the
assignment of a [3 + 3] assembly (Figures S8 and S9). Among
these were a peak at m/z 623.62 corresponding to an intact [M
5OTf] core (Figure 3a). For metallacycle 2, two such peaks
were found (Figures S12 and S13), including a peak at m/z
00.82 corresponding to an intact [M − 5OTf] core (Figure
3b). All of these peaks correspond to intact triangular
metallacycles that become charged resulting from the loss of
triflate counterions. Furthermore, the isotropic distributions
were all in good agreement with those predicted from
simulation. In a 2D diffusionꢀordered spectroscopy (DOSY)
experiment, the observation of a single band supports the
formation of a single product (Figures S14 and S15). The
measured diffusion coefficients of metallacycles 1 and 2 were
5+
−
5
+
6
Figure 4. Fluorescence emission spectra of metallacycles 1 (a)
and 2 (b) in different solvents (λex = 556 nm, c = 1.00 ꢀM).
Photographs of 1 (c) and 2 (d) under UV lamp at 365 nm in
different solvents (c = 1.00 ꢀM). DMSO, dimethylsulfoxide;
DMF, dimethylformamide; DMA, Dimethylacetamide.
−10
−10
2
found to be 4.23 × 10 and 4.31 × 10 m /s, respectively.
Photophysical Studies. The UV–vis absorption spectra of
the BODIPY ligand 3 and triangular metallacycles 1 and 2
were recorded in solvents with different polarities (Figures
S21a, S22a, and S23a). The spectra showed similar absorption
bands at around 556 nm, which was attributed to the π–π*
Cell Imaging and in Vitro Anticancer Treatment.
Nanoparticles (NPs) containing metallacycle 1 or 2 were
5a
prepared through the matrixꢀencapsulation method. Solution
8
c
transition of the BODIPY moieties.
of these NPs of 1 or 2 exhibited a clear Tyndall effect (Figure
S27 insets), supporting the existence of nanoaggregates.
Transmission electron microscopy (TEM) and dynamic light
scattering (DLS) techniques were used to reveal the
3
ACS Paragon Plus Environment

Journal of the American Chemical Society
morphology and size of these nanostructures. Solid spherical
Page 4 of 8
fluorescence intensity arising from 1 or 2 was much higher
than that of the BODIPY ligand 3 under the same conditions,
indicating that HeLa cells had a faster uptake rate and higher
intracellular accumulation after incubation with the NPs
containing metallacycle 1 or 2. For example, HeLa cells
ingested about four times the amount of the NPs containing
metallacycle 1 or 2 than the BODIPY ligand 3 after incubation
for 4 h. The reason was that the cationic nature of the NPs was
favorable for the cellular internalization because the potential
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
structures with an average diameter of ∼40 nm formed from 1
were observed in the TEM image (Figure S26a). In DLS
experiment, a unimodal peak distribution with an effective
average hydrodynamic diameter of 42 nm was observed
(
Figure S27a), in good agreement with the result obtained
from TEM experiments. Metallacycle 2 also formed spherical
aggregates with diameters of ~45 nm (Figure S26b). Similar
DLS experiment showed an average diameter of ∼48 nm
11
(
Figure S27b), consistent with the TEM measurements.
of cell membrane is negative (Figures S29 and S30).
Furthermore, the in vitro stability of the nanoparticles was
evaluated in phosphateꢀbuffered saline (PBS) containing 10%
fetal bovine serum (FBS) at 37 °C. No obvious size variations
were observed over 20 h, confirming the excellent stability of
these NPs under physiological conditions (Figure S28).
Inductively coupled plasma optical emission spectrometry
ICPꢀOES) was performed to determine the amounts of Pt
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(
internalized by HeLa cells after incubation with metallacycles
12
1
and 2. The amounts of Pt in cells treated with both SCCs
continued to increase over 24 h (Figures 5m and S33). For 1,
Confocal laser scanning microscopic (CLSM) and flow
cytometry (FCM) investigations were carried out to confirm
that the NPs containing the metallacycles 1 or 2 were
the accumulation of Pt in HeLa cells was determined to be 653
6
ng/10 cells after 24 h incubation. For 2, the accumulation of
6
Pt in HeLa cells was determined to be 713 ng/10 cells after 24
5a
internalized by human cervical cancer cells (HeLa). Cells
were counterstained with 4',6ꢀdiamidinoꢀ2ꢀphenylindole
h incubation, which was much higher than that of free Pt(II)
6
acceptor 5 (274 ng/10 cells). These observations indicated
(DAPI) or fluorescein isothiocyanate (FITC)ꢀlabeled
that the cellular uptakes of Pt complexes were improved by
formation of metallacycles.
The cytotoxicities of Pt(II) acceptors 4 and 5 and
metallacycles 1 and 2 against HeLa cells were evaluated by a
phalloidin to differentiate the nuclear or cytoplasmic region.
As shown in Figure 5, the HeLa cells exhibited strong
intracellular fluorescence after incubation with the NPs
containing the metallacycles 1 or 2 for 8 h. The amount of the
NPs containing the metallacycles 1 or 2 internalized by HeLa
cells was quantified by FCM (Figure S31). The mean
3
ꢀ(4´,5´ꢀdimethylthiazolꢀ2´ꢀyl)ꢀ2,5ꢀdiphenyltetrazolium
bromide (MTT) assay with different concentrations (Figure 5n
and Table S3). Cisplatin was used as a standard drug in killing
HeLa cancer cells with the 50% growth inhibitory
concentration (IC ) value (0.81 ꢀM). Metallacycle 1 displayed
50
potent cytotoxicity, with the IC50 value (6.41 ꢀM) comparable
to that of free Pt(II) acceptor 4 (3.60 ꢀM). For metallacycle 2,
the IC50 value was 2.11 ꢀM, which was also comparable to
that of free Pt(II) acceptor 5 (1.76 ꢀM). For FDAꢀapproved
platinumꢀbased anticancer drugs, such as cisplatin, carboplatin,
and oxaliplatin, their nonꢀfluorescent nature becomes an
obstacle for tracking the processes of translocation, drug
release and excretion of anticancer agents. The introduction of
BODIPY into the SCCs introduces a fluorophore which is
absent from traditional Ptꢀbased drugs, thereby enabling
fluorescence imagingꢀguided cancer therapy.
In Vitro Photodynamic Therapy. Benefitting from their
easy modifications, low dark toxicities, high photostability,
sharp fluorescence emissions with high fluorescence quantum
yields, and high extinction coefficients, BODIPY derivatives
1
3
are ideal photodynamic agents for cancer PDT. The
1
generation of singlet oxygen ( O ) by the metallacycles was
2
monitored by using singlet oxygen sensor green (SOSG) as a
1
probe with highly selectivity for O . The fluorescence of
2
SOSG is silent in its intact form while becomes much brighter
1
after reaction with O . As shown in Figures 6c and S34, the
2
Figure 5. Confocal laser scanning microscopy (CLSM)
images of HeLa cells after incubation with the ligand 3 and
metallacycles 1 and 2 for 8 h: (a,e,i) stained with DAPI
fluorescence emission at 532 nm increased rapidly upon light
1
irradiation, confirming the successful generation of O2.
Anthraceneꢀ9,10ꢀdipropionic acid disodium (ADPA) was
employed as an indicator to further demonstrate the singlet
oxygen generation. Negligible changes in ADPA absorption
was observed for the metallacycles without light irradiation,
while a gradual decrease in ADPA absorption occurred upon
irradiation of the aqueous solution containing the
photosensitizers (Figures 6d and S35), an indication of singlet
oxygen generation. In comparison, the relative changes in
ADPA absorbance of BODIPY ligand 3 was slower than those
(nucleus); (b,f,j) stained with FITC (βꢀactin); (c,g,k)
fluorescent image; (d) merged image from (a), (b), and (c); (h)
merged image from (e), (f), and (g); (l) merged image from
(i), (j), and (k). (m) Quantitative analysis of the Pt amounts in
HeLa cells after incubation with metallacycles 1 and 2 for 1 h,
4 h, 8 h, and 24 h, respectively. (n) Cytotoxicity of
metallacycles 1 and 2 towards HeLa cells after 24 h
incubation.
4
ACS Paragon Plus Environment

Page 5 of 8
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 6. CLSM images of HeLa cells after incubation with 2 and DCFꢀDA in the (a) absence and (b) presence of vitamin C. (c)
1
Fluorescence enhancement of a SOSG solution by O generated by 2. (d) UVꢀvis spectra of APDA in the presence of 2 upon light
2
2
irradiation (400−700 nm, 50 mW/cm ) for different times. (e) Relative absorbance changes of APDA at 378 nm with 500 nM of 2 or 3
in the light and dark. (f) Cytotoxicity of 2 and 3 against HeLa cells with light irradiation. (g) Cytotoxicity of different formulations
against drug resistant A2780cis cells. (h) Flowꢀcytometric analysis of AnnexinꢀV/PI dualꢀstaining of HeLa cells after different
treatments (I: 2, II: 5, III: cisplatin, IV: 3 + light, V: 3 + 5 + light, VI: 2 + light). The concentration of the formulations was 1.00 ꢀM.
of the metallacycles (Figures 6e and S36), suggesting better
The IC50 value of 3 was determined to be 4.88 ꢀM upon light
irradiation (Figure 6f). Excitingly, the IC50 values of 1 and 2
were decreased to 0.95 and 0.37 ꢀM, respectively. Compared
with these data, we knew that 2 exhibited better anticancer
efficacy, possibly arising from its higher cytotoxicity and
more internalization efficiency. The combination indexes (CI)
were calculated to be 0.56 and 0.48, respectively. The CI
values are much lower than 1, suggesting excellent synergistic
effect is achieved for the SCCs integrating PDT and
chemotherapy.
1
O generation ability by the formation of metallacycles.
2
1
To assess the intracellular O generation by these SCCs
2
after internalization, dichlorofluorescein diacetate (DCFꢀDA)
was chosen as an oxidantꢀsensitive fluorescent dye to detect
the formed reactive oxygen species, which rapidly oxidized
DCFꢀDA into highly fluorescent dichlorofluorescein (DCF).
For the cells cultured with the SCCs, strong green
fluorescence signal from DCF was monitored inside the cells
upon light irradiation (Figures 6a and S37a), which was
1
indicative of efficient O2 generation. In contrast, the
Drug resistance, both inherent and acquired, is the main
reason for the failure of platiumꢀbased anticancer drugs,
greatly limiting their utility in cancer treatments. In order to
enhance the anticancer efficacy, combination therapy is widely
employed to combat drug resistance by “collecting” the merits
of different therapeutic modalities. PDT using the generated
fluorescence signal related to DCF significantly decreased by
preꢀtreating the cells with reactive oxygen species scavenger
vitamin C (50 ꢀM) (Figures 6b and S37b), further verifying
1
the intracellular O2 production in the presence of light
irradiation.
1
Encouraged by these observations, we evaluated the
synergistic anticancer effect of these SCCs against HeLa cells.
O2 to incude cell apoptosis/necosis by oxidating
DNA/proteins inside cells, is an ideal complementary
5
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 8
treatment to chemotherapy, thus realizing synergetic
selfꢀassembled BODIPYꢀplatinum supramolecular triangles
provides promising platform for fluorescence
imagingꢀguided cancer therapy.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
anticancer efficacy to overcome drug resistance through a
multipronged assault. From MTT assay shown in Figure 6g,
the IC50 values against drug resistant A2780cis cells were
measured to be 12.9, 14.2, 18.1, 6.09, 4.43, and 0.76 ꢀM for
cisplatin, 5, 2, 3 + light, 3 + 5 + light, and 2 + light,
respectively. In vivo toxicity studies demonstrated that the
combination of PDT and chemotherapy (2 + light) was up to
one order of magnitude more potent than the chemotherapy
alone (2), and its cytotoxicity was around 9ꢀfold higher than
that of the FDAꢀapproved cisplatin, confirming the
outstanding anticancer efficacy against drugꢀresistant cancer
cell. Compared with the metallacycle, the anticancer efficacy
decreased effectively by simply mixing the chemotherapeutic
and photosensitizer upon light irradiation (3 + 5 + light)
because of its relatively low internalization and photodynamic
effect, which emphasized that the formation of metallacycle
played a vital role in enhancing its anticancer performance.
Moreover, the CI value of 2 + light was calculated to be 0.843,
which verified its remarkable synergistic effect.
a
ASSOCIATED CONTENT
Supporting Information
Experimental details, NMR spectra, and other materials. These
material are available free of charge via the Internet at
http://pubs.acs.org.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
AUTHOR INFORMATION
Corresponding Authors
*guocanyu@zju.edu.cn
*fhuang@zju.edu.cn
*trcook@buffalo.edu
Notes
The authors declare no competing financial interest.
In order to provide more information of the synergetic
efficacy of PDT and chemotherapy, AnnexinꢀV FITC and
propidium iodide (PI) dualꢀstaining assay was conducted to
quantitatively distinguish viable cells from dead cells by flow
cytometry. Due to their low anticancer efficacy against
A2780cis cells, chemotherapy alone (cisplatin, 5, or 2) rarely
induced cell apoptosis (Figure 6h). For PDT alone, a total of
ACKNOWLEDGMENTS
F.H. thanks the National Natural Science Foundation of China
(21434005) and the Fundamental Research Funds for the Central
Universities for financial support. T.R.C. thanks the University at
Buffalo and the State University of New York (SUNY) Research
Foundation, SUNY Fredonia for the use of their Xꢀray
diffractometer, and the National Center for Research Resources
(S10RR029517) for financial support.
2
6.7% A2780cis cells showed apoptosis/necrosis after
2
irradiation for 5 min with the power of 50 mW/cm .
Additionally, the apoptotic/necrotic percentage increased to
REFERENCES
3
3.6% for the cells treated with the mixture of 3 and 5
1
2
3
(a) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B. Acc. Chem.
Res. 2005, 38, 369–378. (b) Oliveri, C. G.; Ulmann, P. A.;
Wiester, M. J.; Mirkin, C. A. Acc. Chem. Res. 2008, 41,
1618–1629. (c) Chakrabarty, R.; Mukherjee, P. S.; Stang, P. J.
Chem. Rev. 2011, 111, 6810–6918. (d) Cook, T. R.; Zheng,
Y.ꢀR.; Stang, P. J. Chem. Rev. 2013, 113, 734–777. (e) Cook, T.
R.; Stang, P. J. Chem. Rev. 2015, 115, 7001–7045. (f) McConnell,
A. J.; Wood, C. S.; Neelakandan, P. P.; Nitschke, J. R. Chem. Rev.
followed by irradiation. Notably, the population of apoptotic
and necrotic cells treated with 2 + light was 46.9%, much
higher than the other formulations, in good agreement with the
results obtained from MTT assay. Similarly, metallacycle 1
also exhibited superior anticancer efficacy and synergistic
effect against A2780cis cells (Figures S38 and S39). Together,
these studies demonstrated that these metallacycles 1 and 2
exhibited potential applications in imagingꢀguided cancer
therapy, endowing the platinumꢀbased chemotherapeutic
agents with diagnostic/imaging capability, which could be
used to trace their delivery, release, and efficacy in vitro and
in vivo.
2
015, 115, 7729–7793. (g) Yamashina, M.; Sartin, M. M.; Sei,
Y.; Akita, M.; Takeuchi, S.; Tahara, T.; Yoshizawa, M. J. Am.
Chem. Soc. 2015, 137, 9266–9269. (h) Yan, X.; Cook, T. R.;
Wang, P.; Huang, F.; Stang, P. J. Nat. Chem. 2015, 7, 342–348.
(i) Oldacre, A. N.; Friedman, A. E.; Cook, T. R. J. Am. Chem.
Soc. 2017, 139, 1424–1427. (j) Gupta, G.; Das, A.; Panja, S.; Ryu,
J. Y.; Lee, J.; Mandal, N.; Lee, C. Y. Chem. Eur. J. 2017, 23,
17199–17203.
(a) Therrien, B.; SüssꢀFink, G.; Govindaswamy, P.; Renfrew, A.
K.; Dyson, P. J. Angew. Chem., Int. Ed. 2008, 47, 3773–3776. (b)
Chen, L.ꢀJ.; Ren, Y.ꢀY.; Wu, N.ꢀW.; Sun, B.; Ma, J.ꢀQ.; Zhang,
L.; Tan, H.; Liu, M.; Li, X.; Yang, H.ꢀB. J. Am. Chem. Soc. 2015,
CONCLUSIONS
In summary, we report here the first examples of highly
emissive Pt(II) supramolecular triangles bearing
pyridineꢀfunctionalized BODIPY ligand
a
via
1
37, 11725–11735. (c) Frischmann, P. D.; Kunz, V.; Würthner, F.
coordinationꢀdriven selfꢀassembly for theranostic studies. The
formation of two triangular metallacycles was fully
Angew. Chem., Int. Ed. 2015, 54, 7285–7289. (d) Gupta, G.; Das,
A.; Ghate, N. B.; Kim, T.; Ryu, J. Y.; Lee, J.; Mandal, N.; Lee, C.
Y. Chem. Commun. 2016, 52, 4274–4277. (e) Zhou, Z.; Yan, X.;
Saha, M. L.; Zhang, M.; Wang, M.; Li, X.; Stang, P. J. J. Am.
Chem. Soc. 2016, 138, 13131–13134. (f) Samanta, S. K.;
Moncelet, D.; Briken, V.; Isaacs, L. J. Am. Chem. Soc. 2016, 138,
14488–14496. (g) Zhang, Y.; Crawley, M. R.; Hauke, C. E.;
Friedman, A. E.; Cook, T. R. Inorg. Chem. 2017, 56, 4258–4262.
(h) Zheng, W.; Yang, G.; Shao, N.; Chen, L.ꢀJ.; Ou, B.; Jiang,
S.ꢀT.; Chen, G.; Yang, H.ꢀB. J. Am. Chem. Soc. 2017, 139,
1
31
characterized by multinuclear NMR ( H and P), ESIꢀMS, 2D
DOSY, UV–vis spectroscopy, and fluorescence spectroscopy.
These triangles possessed promising potential applications in
cancer theranostics, in which the platinum acceptors were
toxic chemotherapeutics and the BODIPY donor was imaging
probe and photosensitizer. In vitro studies demonstrated that
the formation of metallacycles improved their anticancer
efficacy, and the combination of PDT and chemotherapy
showed excellent synergistic effect. More importantly, these
SCCs exhibited superior anticancer outcomes agaist drug
resistant A2780cis cells integrating two different therapeutic
modalities into the supramolecular platforms. The
1
3811–13820.
(a) Li, S.; Huang, J.; Cook, T. R.; Pollock, J. B.; Kim, H.; Chi,
K.ꢀW.; Stang, P. J. J. Am. Chem. Soc. 2013, 135, 2084–2087. (b)
Yan, X.; Li, S.; Cook, T. R.; Ji, X.; Yao, Y.; Pollock, J. B.; Shi,
Y.; Yu, G.; Li, J.; Huang, F.; Stang, P. J. J. Am. Chem. Soc. 2013,
6
ACS Paragon Plus Environment

Page 7 of 8
Journal of the American Chemical Society
1
35, 14036–14039. (c) Yan, X.; Cook, T. R.; Pollock, J. B.; Wei,
P.; Zhang, Y.; Yu, Y.; Huang, F.; Stang, P. J. J. Am. Chem. Soc.
014, 136, 4460–4463. (d) Li, S.; Huang, J.; Zhou, F.; Cook, T.
R.; Yan, X.; Ye, Y.; Zhu, B.; Zheng, B.; Stang, P. J. J. Am. Chem.
Soc. 2014, 136, 5908–5911. (e) Ye, Y.; Cook, T. R.; Wang, S.ꢀP.;
Wu, J.; Li, S.; Stang, P. J. J. Am. Chem. Soc. 2015, 137,
11896–11899. (f) Zhou, J.; Yu, G.; Huang, F. Chem. Soc. Rev.
2017, 46, 7021–7053.
(a) Cook, T. R.; Vajpayee, V.; Lee, M. H.; Stang, P. J.; Chi,
K.ꢀW. Acc. Chem. Res. 2013, 46, 2464–2474. (b) Grishagin, I.
V.; Pollock, J. B.; Kushal, S.; Cook, T. R.; Stang, P. J.; Olenyuk,
B. Z. Proc. Natl. Acad. Sci. U. S. A. 2014, 111, 18448–18453. (c)
Chan, A. K.ꢀW.; Lam, W. H.; Tanaka, Y.; Wong, K. M.ꢀC.; Yam,
V. W.ꢀW. Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 690–695. (d)
Zheng, Y.ꢀR.; Suntharalingam, K.; Johnstone, T. C.; Lippard, S. J.
Chem. Sci. 2015, 6, 1189–1193.
(a) Yu, G.; Cook, T. R.; Li, Y.; Yan, X.; Wu, D.; Shao, L.; Shen,
J.; Tang, G.; Huang, F.; Chen, X.; Stang, P. J. Proc. Natl. Acad.
Sci. U. S. A. 2016, 113, 13720–13725. (b) Yu, G.; Zhang, M.;
Saha, M. L.; Mao, Z.; Chen, J.; Yao, Y.; Zhou, Z.; Liu, Y.; Gao,
C.; Huang, F.; Chen, X.; Stang, P. J. J. Am. Chem. Soc. 2017, 139,
1
2
3
4
5
6
7
8
9
2
4
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
5
6
1
5940–15949.
(a) Lee, C. Y.; Farha, O. K.; Hong, B. J.; Sarjeant, A. A.; Nguyen,
S. T.; Hupp, J. T. J. Am. Chem. Soc. 2011, 133, 15858–15861. (b)
Musser, A. J.; Neelakandan, P. P.; Richter, J. M.; Mori, H.;
Friend, R. H.; Nitschke, J. R. J. Am. Chem. Soc. 2017, 139,
1
2050–12059.
7
8
(a) Zhang, M.; Li, S.; Yan, X.; Zhou, Z.; Saha, M. L.; Wang,
Y.ꢀC.; Stang, P. J. Proc. Natl. Acad. Sci. U. S. A. 2016, 113,
1
1100– 11105. (b) Saha, M. L.; Yan, X.; Stang, P. J. Acc. Chem.
Res. 2016, 49, 2527–2539.
(a) KaloudiꢀChantzea, A.; Karakostas, N.; Raptopoulou, C. P.;
Psycharis, V.; Saridakis, E.; Griebel, J.; Hermann, R.; Pistolis, G.
J. Am. Chem. Soc. 2010, 132, 16327‒16329. (b) Zhang, M.; Saha,
M. L.; Wang, M.; Zhou, Z.; Song, B.; Lu, C.; Yan, X.; Li, X.;
Huang, F.; Yin, S.; Stang, P. J. J. Am. Chem. Soc. 2017, 139,
5067–5074. (c) Gupta, G.; Das, A.; Park, K. C.; Tron, A.; Kim,
H.; Mun, J.; Mandal, N.; Chi, K.ꢀW.; Lee, C. Y. Inorg. Chem.
2
017, 56, 4615–4621.
(a) Ulrich, G.; Ziessel, R.; Harriman, A. Angew. Chem., Int. Ed.
008, 47, 1184‒1201. (b) Yin, X.; Li, Y.; Zhu, Y.; Jing, X.; Li,
Y.; Zhu, D. Dalton Trans. 2010, 39, 9929–9935.
9
2
10 Williams, A. T. R.; Winfield, S. A.; Miller, J. N. Analyst 1983,
108, 1067–1071.
1 (a) Sun, C.ꢀY.; Shen, S.; Xu, C.ꢀF.; Li, H.ꢀJ.; Liu, Y.; Cao, Z.ꢀT.;
1
Yang, X.ꢀZ.; Xia, J.ꢀX.; Wang, J. J. Am. Chem. Soc. 2015, 137,
1
5217−15224. (b) Li, H.ꢀJ.; Du, J.ꢀZ.; Du, X.ꢀJ.; Xu, C.ꢀF.; Sun,
C.ꢀY.; Wang, H.ꢀX.; Cao, Z.ꢀT.; Yang, X.ꢀZ.; Zhu, Y.ꢀH.; Nie, S.;
Wang, J. Proc. Natl. Acad. Sci. U. S. A. 2016, 113, 4164−4169.
12 Xiao, H.; Qi, R.; Liu, S.; Hu, X.; Duan, T.; Zheng, Y.; Huang, Y.;
Jing, X. Biomaterials 2011, 32, 7732–7739.
3 Kamkaew, A.; Lim, S. H.; Lee, H. B.; Kiew, L. V.; Chung, L. Y.;
1
Burgess, K. Chem. Soc. Rev. 2013, 42, 77–88.
7
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 8
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
TOC Graphic:
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
8
ACS Paragon Plus Environment