Inorganic Chemistry
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PtDP-N NPs could disperse in water uniformly. The loading
content of PtDP-N NPs was calculated by the standard curve
shown in Figure 2a, PtDP-N NPs have uniform sizes with
diameters of around 50 nm, which were measured by
S7, the hydrodynamic size measured by dynamic light
scattering was 92 nm, which was very suitable for
bioapplication. Also, the hydrodynamic size changed negligibly
at 72 h, indicating the excellent stability of PtDP-N NPs in
water. In addition, the energy-dispersive X-ray spectrum of
PtDP-N NPs verifies the presence of the Pt atom (Figure S8).
The presence of Pt(II) ions in the obtained nanoparticles was
further confirmed by X-ray photoelectron spectroscopy (XPS).
As shown in Figure 2b, there were two peaks at 71.1 and 74.5
eV, indicating the existence of Pt(4f) in PtDP-N NPs. In
addition, the maximal absorption peak of PtDP-N NPs was at
results demonstrated that the PtDP-N NPs have good O
generation ability for realizing a PDT effect.
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In Vitro Photothermal and Photodynamic Properties
of PtDP-N NPs. With the purpose of exploring the biomedical
applications of PtDP-N NPs, their PDT and PTT effects were
detected in vitro. First, 2′,7′-dichlorofluorescin diacetate
(DCFH-DA, a ROS indicator) was used to detect ROS
generation of PtDP-N NPs in HeLa cells. As shown in
Figure 3a, the green fluorescence was observed in PtDP-N
NPs-treated cells after 5 min of light irradiation (730 nm, 500
mW cm ), while no or weak fluorescence could be seen in the
control groups. The result confirmed the effective ROS
generation ability of PtDP-N NPs in HeLa cells. Next, the
cytotoxicity of PtDP-N NPs was investigated by MTT assays.
The HeLa cells were incubated with PtDP-N NPs at a series of
concentrations. The pretreated cells were irradiated with 730
48
−
2
−
2
nm light (500 mW cm ) for 5 min or not to measure the light
or dark cytotoxicity of PtDP-N NPs. As shown in Figure 3b,
the viability of HeLa cells was more than 80% in the dark even
with concentrations of up to 100 μM, which indicated low dark
cytotoxicity and excellent biocompatibility. Under irradiation,
the viability of PtDP-N NPs-treated HeLa cells sharply
decreased with increasing PtDP-N NPs concentration. When
the concentration of PtDP-N NPs was 20 μM, the viability of
HeLa cells was about 50% of the original value. The results
demonstrated that PtDP-N NPs have a good phototherapy
effect for effectively killing cancer cells. In order to further
illustrate the phototherapy effect of PtDP-N NPs to cause cell
apoptosis and cell death, flow cytometry experiments were
completed via an Annexin V-FITC/propidium iodide (PI) cell
apoptosis kit to ensure the amounts of viable and dead cells of
different stages with the given conditions. As shown in Figure
3c, few HeLa cells were at the late apoptotic stage in the
groups of phosphate-buffered saline (PBS) only, PBS with a
laser, and PtDP-N NPs only. However, 20.8% HeLa cells at
the late apoptotic stage were detected when they were
incubated with PtDP-N NPs and treated with a laser.
Hence, PtDP-N NPs with an excellent phototherapy effect
could effectively inhibit the growth of cancer cells.
To evaluate the synergistic PDT and PTT effects of PtDP-N
NPs, a live−dead cell staining experiment was applied to HeLa
cells. The green fluorescence of Calcein AM and red
fluorescence of PI expressed live and dead cells, respectively.
N-Acetyl-L-cysteine (NAC) could react with ROS to inhibit
the PDT effect of PtDP-N NPs and leave the PTT effect only.
To rule out the fluorescence interference of PtDP-N NPs,
confocal fluorescence (PtDP-N NPs without AM, PI, and
shown in Figure S13, no fluorescence was observed under 488
nm laser irradiation, indicating that PtDP-N NPs cannot affect
this test. As shown in Figure 3d, there was only green
fluorescence before laser irradiation in every group. However,
intense red fluorescence was observed in the PtDP-N NPs and
PtDP-N NPs + NAC groups. Also, the intensity of the green
fluorescence in the PtDP-N NPs group was obviously weaker
than that of the PtDP-N NPs + NAC group. The results
demonstrated that PtDP-N NPs exhibited good synergistic
PDT and PTT effects for killing cancer cells.
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32 nm. As shown in Figure 2c, the absorption band of PtDP-
N NPs in the NIR region was broadened and red-shifted
compared with free PtDP-N, which was caused by π−π
S9, the PtDP-N NPs aqueous solution showed weak
luminescence because of their low luminescent quantum
efficiencies and aggregation-induced quenching.
Photothermal and Photodynamic Properties of PtDP-
N NPs. At first, the photothermal effect of PtDP-N NPs was
investigated. The temperature changes of the PtDP-N NPs
aqueous solution with different concentrations were measured
under continuous irradiation of a 730 nm laser (500 mW
−
2
cm ) for 5 min. As shown in Figure 2e, a quick elevation of
the temperature was observed in the PtDP-N NPs solution at
every concentration, while the temperature of pure water
showed no obvious change. On the basis of the data in Figure
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2
f and the reported method,
the photothermal conversion
efficiency of PtDP-N NPs was calculated as 27.9%. This value
is significantly higher than that of commercial dye ICG
(
15.1%), which has been approved by the Federal Drug
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Administration for NIR photothermal agents. Importantly,
the temperature change of azadipyrromethene nanoparticles
(
7-N NPs) at 30 μM was 15.7 °C (Figure 2e). The results
confirmed that the photothermal effect of PtDP-N was
produced by the azadipyrromethene skeleton. Furthermore,
thermocycling test was performed. As shown in Figure S10,
PtDP-N NPs exhibited a negligible temperature change after
five repeated cycles, suggesting the excellent photothermal
stability of PtDP-N NPs. Hence, PtDP-N still retained
excellent photothermal effect and stability after being
encapsulated in PtDP-N NPs.
Next, the photostability test of PtDP-N NPs was carried out
irradiation of a 730 nm laser. As shown in Figure S11, the
intensity of the maximal absorption peak of PtDP-N NPs
exhibited almost no change even under irradiation for 30 min,
suggesting the excellent photostability of PtDP-N NPs. The
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O generation of PtDP-N NPs was confirmed by monitoring
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the 414 nm absorption changes of DPBF, when the mixed
DPBF, superoxide dismutase, catalase, and PtDP-N NPs
In Vivo Photothermal and Photodynamic Properties
of PtDP-N NPs. Considering the good synergistic PDT and
PTT effects of PtDP-N NPs in cells, the phototherapy effect
on HeLa tumor-bearing mice was further investigated. All
animal experiments conformed to the National Institutes of
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2
solution was irradiated by a 730 nm laser (500 mW cm ). As
shown in Figures 2d and S12, the absorption intensity of DPBF
decreased about 40% after 2 min of irradiation. In contrast, a
slight decrease was observed in the DPBF-only group. The
E
Inorg. Chem. XXXX, XXX, XXX−XXX
Feng, Teng
