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ChemComm
DOI: 10.1039/C6CC02571D
Journal Name
COMMUNICATION
APMCRs@MB, or APMECRs experiments was observed under that APMECRs can act as good carriers which not only tightly
the laser irradiation (Figure 2d). As expected, only co-existence bind MB, but also retain the optical properties of MB that can
of MB and [Eu(THA)3(phen)] on the APMCRs samples can result be applied for further PDT treatments.
in a high rate of the DPBF decay due to a continuous
The hypoxic cells in solid tumors can produce endogenous
generation of ROS, confirming the ability of APMECRs@MB to H2O2,16 which can react with the catalase shell of
produce ROS via an efficient energy transfer process.
APMECRs@MB to generate O2 in situ and thus enhance the
PDT efficacy upon the 808 nm irradiation via the formation of
ROS. To prove this concept, we cultured the prostatic cancer
(PC-3) cells in a hypoxic incubator under a mixed atmosphere
(0.3% O2, 5% CO2, 94.7% N2). 2,7-Dichlorofluorescin diacetate
(DCFH-DA) was used to detect the generated ROS. In the
presence of ROS, DCFH-DA oxidizes to
dichlorofluorescein (DCF), which emits
a
fluorescent
a
bright green
fluorescence. Confocal images of the DCFH-DA fluorescence
after the 808 nm irradiation in PC-3 cells incubated with
APMECRs@MB (Figure 3a) reveal a strong fluorescence of DCF,
1
suggesting a high O2 production level. In contrast, little or no
fluorescence is seen in the cells that were incubated with
APMERs@MB or free MB, demonstrating a specific H2O2
activation of APMECRs@MB to produce 1O2 in tumor cells.
Besides, the APMECRs@MB NCs are not only highly active
toward the H2O2 activation to produce 1O2 for PDT, but also act
as efficient photothermal agents for PTT due to the
longitudinal SPR peak of AuNRs.17 If irradiated by the 808 nm
laser, a water suspension of APMECRs@MB shows a rapid
increase in temperature and reaches a plateau within 10 min
(Figure S12). Temperature rising rate and final temperature
are proportional to the NCs concentration and laser function
power. This result reveals a great heat generation capacity of
APMECRs@MB for PTT upon irradiation with 808 nm NIR light.
After establishing the PTT effect of APMECRs@MB, we
simulated PTT in deep-set tumor conditions in vitro. In these
experiments, pork tissue of varying thickness was placed
between the NIR laser and PC-3 tumor cells exposed to
APMECRs@MB (Figure S13a), followed by the cell temperature
analysis. With an additional distance between pork tissue and
cells (i.e., the height of the well and the media bathing the
cells), the simulated depths were greater than the measured
thickness of pork tissue. Temperature of cells exceeds 60 °C
after 10 min of the irradiation with 808 nm light (1 W/cm2) in
the experiment with no pork tissue (0 mm, Figure S13b),
whereas tests using the 10 and 14 mm tissue thickness lead to
the ~45 and ~40 °C temperatures, respectively (Figure S13c,d).
These data establish and validate the feasibility of
APMECRs@MB as a NIR-triggered PTT at a deep-tissue level
(>1 cm).
Figure 2. (a) Overlapping between the emission spectrum of [Eu(THA)3(phen)]
(λex = 808 nm, black line) and the UV-vis absorption spectrum of MB (red line).
(b) Emission spectra of APMEs and APMEs@MB (λex
= 808 nm, equal
concentrations of Eu3+). (c) Absorption spectra of the DPBF solution incubated
with APMECRs@MB under irradiation at 808 nm for different time periods (808
nm laser, 1W/cm2). (d) Absorption at 410 nm of DPBF as a function of the 808
nm irradiation time (NIR light alone, incubated with APMCRs@MB, APMECRs, or
APMECRs@MB). (e) Absorption spectra of the DPBF solution incubated with free
MB under irradiation at 660 nm for different time periods. (f) Evolution of the
DPBF absorption profile at 410 nm within several days (incubated with free MB
or APMECRs@MB under 660 or 808 nm irradiation, respectively).
The formation of ROS induced by free MB upon the 660 nm
light irradiation was aslo assessed (Figure 2e). An exposure to
free MB results in a high rate of the DPBF decay, but it
decreases after 6 min due to a poor water-stability of MB. The
1O2 production by free MB decreases within several days
(Figure 2f). However, the formation of 1O2 induced by
APMECRs@MB after the 808 nm light irradiation remains
almost unchanged for at least 5 days, demonstrating a long-
term stability of APMECRs@MB in PBS; this is also confirmed
by fluorescence spectroscopy (Figure S8). Thus, the phenyl
mesoporous channels of APMs with super hydrophobicity
serve as a protector for improving the stability and inhibiting
the premature leaking of MB. Two-photon luminescence (TPL)
spectra of APMECRs under different time intervals and in the
presence of 1O2 were also measured (Figure S9). The Eu3+
emission intensities have no change, suggesting a long-term
stability of APMECRs in PBS and in the presence of 1O2.
Due to a potent activity of catalase shell, APMECRs@MB
quickly reacts with H2O2 to generate O2. This process can be
visually observed as a formation of the O2 bubbles upon
exposure of APMCRs to a low concentration of H2O2 (Figure
S10a), thus confirming the generation of more dissolved O2 (as
evidenced by the quantitative O2 generation experiments,
Figure S10b). In addition, after the incubation with H2O2, the
1O2 generation by APMECRs@MB upon the 808 nm irradiation
in vacuum was tested. A decreased DPBF absorption intensity
upon addition of H2O2 demonstrates a significantly enhanced
To investigate the therapeutic effect of APMECRs@MB, PC-3
cancer cell viabilities were measured after different
treatments. Firstly, the targeting ability of APMECRs@MB was
evaluated using the cRGD-unmodified APMECs@MB
nanosphere as a control. Confocal microscopy and flow
cytometry analysis (Figure S14 and S15) show that
APMECRs@MB exhibits a higher cellular uptake than the
unmodified APMECs@MB. Both APMECRs@MB and
APMECs@MB have no apparent cellular uptake in normal cells.
These results demonstrate the targeting ability of cRGD to
1
production of O2 (Figure S11), mainly via the decomposition
of H2O2 catalyzed by a catalase shell; this can lead to an ultra-
1
efficient O2 production by APMECRs@MB in the hypoxic solid
tumors. Moreover, catalase shell generates O2 and prevents
the leakage of [Eu(THA)3(phen)] and MB. These results indicate
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Chem. Commun., 2015, 00, 1-4 | 3
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