A novel drug-drug nanohybrid for the self-delivery of porphyrin and: Cis-platinum

Article abstract of DOI:10.1039/c9ra07085k

The thriving development of nanotechnology has greatly promoted the development of drug delivery systems (DDSs) in the past decades. However, most DDSs themselves cannot serve as diagnostic reagents and must be metabolized, by which they may become poisonous and even cause immune reactions. In this study, a novel self-delivery drug-drug system (SDDS) nanohybrid based on the coordination assembly of a photodynamic reagent, tetra-(4-carboxyphenyl)porphyrin (TCPP), and a chemotherapy reagent, cis-platinum, was designed and synthesized. The four carboxyl groups of TCPP can compete with the chloride ions of cis-platinum by coordination interactions, forming a TCPP-cis-platinum nanohybrid (PCNH) for the purpose of photodynamic/chemotherapeutic synergistic treatment with a combinational index of 0.28. Meanwhile, the PCNH system can effectively protect the photosensitizer TCPP from photobleaching when irradiated continuously in the photodynamic therapy (PDT) process, which is very crucial for PDT. Furthermore, introduction of the heavy atom platinum can greatly enhance the producing efficiency of ¹O₂ by 46%. In addition, the red emission fluorescence of TCPP is beneficial for monitoring and tracing the process of drug delivery when used in vitro. This work may pave a new way for the design of new integrated nanohybrids for diagnosis and synergistic treatment.

Full text of DOI:10.1039/c9ra07085k

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PAPER
A novel drug–drug nanohybrid for the self-delivery
of porphyrin and cis-platinum†
Cite this: RSC Adv., 2019, 9, 37003
b
a
a
Changfu Shan,a Jiaxi Ru,
Meina Zhang,a Jing Cao,
Weisheng Liu,
*
b
a
*
*
Huichen Guo and Yu Tang
The thriving development of nanotechnology has greatly promoted the development of drug delivery
systems (DDSs) in the past decades. However, most DDSs themselves cannot serve as diagnostic
reagents and must be metabolized, by which they may become poisonous and even cause immune
reactions. In this study, a novel self-delivery drug–drug system (SDDS) nanohybrid based on the
coordination assembly of
a photodynamic reagent, tetra-(4-carboxyphenyl)porphyrin (TCPP), and
a chemotherapy reagent, cis-platinum, was designed and synthesized. The four carboxyl groups of TCPP
can compete with the chloride ions of cis-platinum by coordination interactions, forming a TCPP-cis-
platinum nanohybrid (PCNH) for the purpose of photodynamic/chemotherapeutic synergistic treatment
with
a combinational index of 0.28. Meanwhile, the PCNH system can effectively protect the
photosensitizer TCPP from photobleaching when irradiated continuously in the photodynamic therapy
(PDT) process, which is very crucial for PDT. Furthermore, introduction of the heavy atom platinum can
greatly enhance the producing efficiency of 1O2 by 46%. In addition, the red emission fluorescence of
TCPP is beneficial for monitoring and tracing the process of drug delivery when used in vitro. This work
may pave a new way for the design of new integrated nanohybrids for diagnosis and synergistic treatment.
Received 4th September 2019
Accepted 23rd October 2019
DOI: 10.1039/c9ra07085k
rsc.li/rsc-advances
permeability and retention effect (EPR).7 Numerous research
results show that the EPR effect can enhance the accumulation
of drugs in tumours up to 5 to 10 fold.1 Meanwhile, elaborately
designed drug delivery systems (DDS) can also release their
cargo spatio-temporally when triggered endogenously (pH,
redox, enzymes) or exogenously (light, heat, magnetism, ultra-
sound).8–11 As a result, large amounts of drug carriers have been
developed in the progress of nanomedicine, such as meso-
porous silicon, magnetic nanoparticles, polymer materials,
quantum dots, and gold and carbon nanomaterials.12,13
However, introducing non-drug materials as carriers causes
two problems. One is limited loading efficiency because the
carriers should occupy a certain mass.14 The other is safety
issues. Some of the metabolites of carriers are poisonous and
even cause immune reactions, which brings great risk to
patients and impedes the clinical use of nanomedicines.15 To
resolve these carrier-dependent problems, the self-delivery
concept was proposed, where the carriers are constructed only
from drugs.16 This concept tremendously improves the delivery
efficiency and fundamentally decreases side effects by elimi-
nating the use of non-drug materials as carriers. To the best of
our knowledge, most self-delivery drug–drug systems (SDDS)
are constructed based on covalent bonds or supramolecular
interactions such as hydrogen bonding, p–p stacking, C–H/p
interactions, van der Waals interactions and halogen bonding.17
As a member of the supramolecular interaction family, coordi-
nation interactions between different drugs have rarely been
1 Introduction
Precise diagnosis and treatment are of great signicance for
highly selective and efficient cancer therapy. In traditional
cancer treatments, doxorubicin (DOX), paclitaxel (PTX), camp-
tothecin (CPT) and cis-platinum remain indispensable owing to
their advantages of mature theories and application.1–3
However, these micromolecule drugs possess inherent limita-
tions, including random distribution, poor solubility, low
bioavailability and short cycling periods, which clinically result
in dose-dependent toxicity.4 Beneting from the active devel-
opment of nanotechnology, nanomedicine can endow micro-
molecule drugs with better solubility, chemical stability and
decreased biodegradation or excretion.2,5,6 Certain sizes of
molecules, such as liposomes, nanoparticles, and macromo-
lecular drugs, tend to accumulate in tumour tissue much more
than they do in normal tissues; this is known as the enhanced
aState Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous
Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry
and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China.
E-mail: tangyu@lzu.edu.cn; caoj@lzu.edu.cn
bState Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research
Institute, Chinese Academy of Agricultural Sciences, Lanzhou 730046, P. R. China.
E-mail: guohuichen@caas.cn
† Electronic supplementary information (ESI) available: Synthetic and
experimental details, additional spectra and in vitro experimental data. See DOI:
10.1039/c9ra07085k
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used to construct SDDS. Meanwhile, coordination bonds 2H-tetrazolium (MTS), HOTEST-33258 and 20,70-dichlorodihy-
should be broken in weak acidic neoplastic microenviron- drouorescein diacetate (DCFH-DA) were purchased from
ments; thus, drugs can be released precisely within tumour cells YESEN (Shanghai, China). Fetal bovine serum (FBS) was
by an endogenous trigger.
purchased from Biosharp Life Science (Guangzhou, China). Cell
Herein, we designed a SDDS nanohybrid based on the culture medium was purchased from Hyclone Laboratories, GE
coordination assembly of a photodynamic reagent, 5,10,15,20- Healthcare Life Science (Utah, America). Other reagents were all
tetra(4-carboxylphenyl)porphyrin (TCPP), and a chemotherapy purchased from Rionlon (Tianjin, China).
reagent, cis-dichlorodiammine platinum(II) (cis-platinum)
(Scheme 1). The design strategy of the TCPP-cis-platinum 2.2 Instruments
nanohybrid (PCNH) was established based on coordination
UV-vis absorption spectra were recorded on a UV-vis-NIR spec-
characteristics, where platinum can combine with the carboxyls
trometer (Agilent Technologies, Cary-5000, America); FT-IR
of TCPP more strongly than chloride ions under weak alkaline
spectra were recorded on an FT-IR spectrometer (Bruker,
Vertex 70, Germany) with the KBr method; uorescence spectra
were recorded on a uorescence spectrophotometer (Shimadzu,
conditions. Meanwhile, the four carboxyls of TCPP should be
available to construct topological structures, and cis-platinum
can function as a bridge to link TCPP together. In contrast to
RF5301-PC, Japan; Edinburgh, FLS 920, Germany); near
normal physiological pH (7.2 to 7.4), the extracellular pH
infrared (NIR) spectra were measured by an Edinburgh Instru-
around solid tumours is acidic (pH 6.5 to 6.9), and that in late
ments spectrometer (FLS 920, UK); 1H-NMR spectra were
endosomes is even more acidic (pH 5.5).18 The coordination
recorded on a JNM-ECS 400 MHz spectrometer with TMS as the
internal reference; transmission electron microscopy (TEM)
images and EDX were recorded on a TECNAI G2 with 200 kV
accelerating voltage (TECNAI G2, America); cell images were
recorded on a uorescent microscope with blue light as the
excitation (Olympus, IX71, Japan) or on a laser scanning
bonds between –COOꢀ and Pt can be broken in the weakly
acidic neoplastic microenvironment. Thus, TCPP and cis-plat-
inum can be released from the nanohybrid PCNH, which is
fundamental for synergistic therapy of photodynamic therapy
(PDT) and chemotherapy. Meanwhile, due to the heavy metal
effect of the platinum coordinated with TCPP, the production
confocal microscope (Leica, SP8, Germany). The z-potential was
efficiency of singlet oxygen can be elevated by 46% over TCPP as
recorded on a Malvern Instruments system (UK).
a reference under the same conditions. Also, PCNH can effec-
tively protect the photosensitizer from photobleaching when
continuously irradiated by light, and the red uorescence of
TCPP can be used to monitor the process of drug delivery.
TCPP-OMe was synthesized according to the literature with
2.3 Synthesis of 5,10,15,20-tetra(4-methoxycarbonylphenyl)
porphyrin (TCPP-OMe)
slight modication.19 Methyl-4-formylbenzoate (16.5 g, 100
mmol) was dissolved in n-propionic acid (250 mL), and the
2 Experimental
2.1 Materials
solution was heated to 135 ꢁC until slightly boiling. Newly
distilled pyrrole (6.7 mL) in n-propionic acid (30 mL) was
dropped into the solution within 20 min, and the colour became
All chemicals were used without purication unless otherwise
specied. Methyl-4-formylbenzoate, cis-platinum and pyrrole
were purchased from HEOWNS (Tianjin, China). 3-(4,5-dime-
thylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-
ꢁ
dark. Aer 1 h, the temperature was allowed to cool to 80 C,
and some of the n-propionic acid (100 mL) was removed by
a rotary evaporator. The mixture was stored in a refrigerator (4
ꢁC) overnight and the sediment was ltered, followed by
washing with water and ethanol three times. The crude product
was puried by column chromatography with CH2Cl2 as the
eluent. 1H-NMR (400 MHz, DMSO-d6): d 8.81 (s, 8H), 8.44 (d, 8H,
J ¼ 8.4 Hz), 8.29 (d, 8H, J ¼ 8.4 Hz), 4.10 (s, 12H), ꢀ2.83 (s, 2H).
Micro-TOF, m/z calcd [M + H]+: 846.27, found: 846.40.
2.4 Synthesis of 5,10,15,20-tetra(4-carboxylphenyl)porphyrin
(TCPP)
TCPP was synthesized by hydrolysing TCPP-OMe. Briey, TCPP-
OMe (500 mg) was transferred into a mixed solution containing
methanol (100 mL), THF (50 mL) and 40% KOH (12 mL). Aer
ꢁ
the mixture was heated at 40 C for 4 h, the temperature was
allowed to cool to R.T. and the pH was adjusted to 4 to 5 by
adding concentrated hydrochloric acid in an ice-water bath.
Next, the sediment was removed by ltration, and the TCPP was
obtained by removing the solvent using a rotary evaporator.
Lastly, the crude product was washed with large amounts of
water and CH2Cl2. 1H-NMR (400 MHz, DMSO-d6): d 13.0 (S,
Scheme 1 Illustration of the synthetic procedure of PCNH and the
imaging-guided synergetic therapy of PDT and chemotherapy.
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COOH), 8.38 (d, 8H, J ¼ 8.0 Hz), 8.32 (d, 8H, J ¼ 8.0 Hz), ꢀ2.86 Aer 3 h, the optical density (OD) at 490 nm was recorded.
(s, 2H).Micro-TOF, m/z calcd [M + H]+ m/z ¼ 791.21, found m/z ¼ Meanwhile, to verify the effects of photodynamic therapy, the
791.18.
experimental procedures were repeated, except that the 96-well
plates were irradiated by an LED lamp (the total power was 20 W
and the time was 10 min). The cell viability was calculated
according to the formula below:
2.5 Synthesis of porphyrin cis-platinum nanohybrid (PCNH)
cis-Platinum (15.0 mg) in DMF (1 mL) was dropped into DMF
(25 mL) which contained TCPP (19.8 mg) within 10 min. When
the temperature was elevated to 120 C, triethylamine (80 mL,
Cell viability (%) ¼ (ODdrug/ODcontrol)ꢂ100%
ꢁ
120 mL, 160 mL, 320 mL and 640 mL, respectively) was dropped
within 2 days; then, the temperature was allowed to cool to
room temperature. Meanwhile, to study the assembly behaviour
in water, TCPP was dissolved in water and the pH was adjusted
to 8. Then, cis-platinum in 5 mL wateꢁr was added dropwise, and
the temperature was elevated to 50 C for 8 h. PCNH was ob-
tained by centrifugation (18 000 r, 20 min) and washed with
DMF and water. Finally, the PCNH was dried with freeze drying
equipment.
where ODdrug refers to the OD value with the addition of TCPP,
cis-platinum or PCNH and ODcontrol refers to the OD value of
a well without addition of TCPP, cis-platinum or PCNH.
2.9 Test of singlet oxygen in vitro
The singlet oxygen in vitro was tested in a Petri dish. In brief,
HeLa cells were cultured for 3 h. Then, 1 mL DCFH-DA was
added, and the culture was continued for another 20 min. The
uorescence images were recorded on a confocal laser scanning
microscope or uorescence microscope with green light exci-
tation. To record the increasing uorescence intensity of singlet
oxygen, photos were taken every 2 min with blue light as
excitation.
2.6 Determination of uorescence quantum yields
TCPP and PCNH were dissolved or distributed in D2O, and the
pH value was adjusted to 7.24 with triethylamine. The absor-
bance was controlled below 0.05 under the special peaks. The
uorescence data were subsequently collected. Fluorescence
quantum yields were calculated according to the formula below:
3 Results and discussion
As mentioned above, PCNH was synthesized based on
competitive coordination of the carboxyls (–COOH) of TCPP
against the chloride ions of cis-platinum. Because the coordi-
nation ability of carboxyls is greatly inuenced by the deproto-
nation degree, the shape of PCNH varied from rods with
micron-sized lengths to spheres with 117 nm in diameter
when the amount of triethylamine was varied. However, when
a larger amount of triethylamine was added, the nanoparticles
become crosslinked (Fig. S3, ESI†). On the other hand, when the
assembly proceeded in water, the morphology became severely
crosslinked. All the mentions of PCNH below refer to the
117 nm nanospheres from the transmission electron micro-
scope image (Fig. 1a). The average hydrodynamic diameter of
PCNH characterized by dynamic light scattering (DLS) is
168 nm (Fig. 1b); this is slightly larger than the value obtained
by TEM, which can be ascribed to the dry state in TEM and the
hydrodynamic diameter in DLS.22 Meanwhile, the energy-
dispersive X-ray (EDX) (Fig. 1c) and energy dispersive
F1/F2 ¼ (A2ꢂF1)/(A1ꢂF2)
where F refers to the uorescence quantum yield, A refers to the
absorbance value and F refers to the integral area of the uo-
rescence spectrum.
2.7 Calculation of combination index (CI)
The combination index is an important parameter to distin-
guish different drugs that have synergistic, antagonistic or
additive effects when used simultaneously. CI was calculated
using the following formula:20
CI ¼ D1/Df1 + D2/Df2 + D1D2/Df1Df2
where Df1 is the dose of TCPP alone required to achieve X
percent viability and D1 is the dose of TCPP in PCNH required to
achieve the same cell viability. Similarly, Df2 is the dose of cis-
platinum alone required to achieve X percent viability and D2 is
the dose of cis-platinum in PCNH required to achieve the same
cell viability. In this paper, X equals 50%, that is, the IC50 value.
2.8 Test of cytotoxicity in vitro
The cytotoxicity was tested on HeLa cells using the MTS
method.21 In short, HeLa cells were cultured in 96 well plates at
a density of 5000 cells per well with 10% FBS cell culture
medium at 37 ꢁC in a 5% CO2 atmosphere. The experiment was
conducted in the dark rst. PCNH, TCPP and cis-platinum were
added respectively, and the concentrations were 2.5 mg mLꢀ1
5.0 mg mLꢀ1, 10.0 mg mLꢀ1, 20.0 mg mLꢀ1, and 40.0 mg mLꢀ1
,
,
respectively (the concentration corresponds to pure TCPP and
Fig. 1 TEM ((a), scale bar 1 mm), DLS (b), EDX (c), and STEM results and
TCPP in PCNH); 24 h later, 10 mL MTS was added to each well. EDS elemental mapping of PCNH ((d), scale bar 100 nm).
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spectrometer (EDS) elemental mapping data (Fig. 1d) clearly stretching vibration peak at 1704 cmꢀ1 from the C]O of
demonstrate that carbon, nitrogen, oxygen and platinum were –COOH was bathochromically shied. The peaks located at
successfully integrated into PCNH.
1601 cmꢀ1, 1534 cmꢀ1, 1396 cmꢀ1, and 1360 cmꢀ1 belong to
Fig. 2a shows the normalized UV-vis absorption of TCPP and nas(COOꢀ) and ns(COOꢀ). The band gap between 1601 cmꢀ1 and
PCNH. The characteristic absorption peak of TCPP, which 1396 cmꢀ1 is 205 nm, which implies that the carboxyl is
belongs to the Soret band, was located at 419 nm. Meanwhile, a monodentate ligand in this situation.26,27 The characteristic
the remaining four peaks at 515 nm, 550 nm, 589 nm and peak of the pyrrole ring N–H rocking vibration at 966 cmꢀ1 was
646 nm are the peaks of the Q bands. Compared with TCPP, the still present, indicating that the platinum ions mainly coordi-
peaks of the Q bands in PCNH are bathochromically shied, nate with the carboxyls rather than the porphyrin rings.
while the Soret band in PCNH stayed the same; this is different
X-ray photoelectron spectroscopy (XPS), a highly surface-
from a pyrrole ring-metal complex, in which case the Soret band sensitive probe, was also used to ascertain the success of the
moved obviously.23 Importantly, as shown in Scheme 1, the design strategy. Binding energies centred at ca. 75.7 eV,
combination of TCPP and cis-platinum was achieved via the 199.5 eV, 284.8 eV, 401.6 eV and 533.1 eV were assigned to Pt 4f,
coordination of platinum with carboxyl groups rather than the Cl 2p, C 1s, N 1s and O 1s, respectively. In contrast with cis-
pyrrole ring. As a result, the symmetry of the pyrrole ring will platinum, the peak of Cl 2p disappeared completely, which
not be inuenced; thus, the energy levels will not be degenerate. intuitively shows that the chloride ions were removed in PCNH
Gratifyingly, the number of Q bands did not decrease, which (Fig. S4, ESI†). The platinum in PCNH functioned as a bridge to
implies that the symmetry indeed does not change and that no link TCPP together by coordination. To further analyse the
degeneracy of energy levels occurred. From these, we inferred coordination environment of the platinum ions, the ne spec-
that the platinum ions were coordinated with the carboxyls in trum of Pt 4f was examined. The binding energies located at
the nanohybrid.24 As such, the molar ratio of [TCPP4ꢀ] and 75.75 eV and 72.49 eV belong to Pt 4f5/2 and Pt 4f7/2 of pure cis-
[Pt(NH2)2]2+ in PCNH is 1 : 2, which implies that the theoretical platinum (Fig. 2c). However, both binding energies increased
mass percent of platinum is 31.9%. ICP-MS gave a result of when cis-platinum coordinated with TCPP to construct PCNH
30.5% for the mass percent of platinum in PCNH, which is (Fig. 2d), which can be explained by the fact that the coordi-
consistent with the theoretical value. Meanwhile, the surface nation bond with platinum became stronger. Importantly, the
potential is an important parameter for drug delivery carriers binding energies of the Pt–N bond at 76.61 eV and 73.13 eV were
because it greatly inuences the mobility and cycling time when maintained.28 However, the peaks at 75.75 eV and 72.41 eV
used in vivo. In comparison with TCPP, the x potential of PCNH which belong to the Pt–Cl binding energy vanished in PCNH.29
increased because of the positive value of cis-platinum (Table Meanwhile, two peaks at 75.87 eV and 72.43 eV appeared, which
S1, ESI†). Simultaneously, a slight negative potential is bene- can be assigned to the Pt–O bond. The XPS data provide strong
cial for PCNH to circulate in blood vessels.25
Fourier transform infrared (FT-IR) spectra were also used to between the carboxyls and platinum ions (Fig. 2d).
verify the combination mode of TCPP with cis-platinum Beneting from the long wavelength uorescence emission
evidence that PCNH was constructed by coordination bonding
(Fig. 1d). Aer assembling with TCPP to form PCNH, the of porphyrin, PCNH can be used as a good imaging reagent for
tracing and diagnosis. The emission peaks for both TCPP and
Fig. 2 Normalized UV-vis spectra of TCPP and PCNH ((a); the insert is Fig. 3 Fluorescence spectra (a) and singlet oxygen fluorescence
the amplification figure of the Q bands). FT-IR spectra of TCPP, cis- spectra of TCPP and PCNH (b). Fluorescence lifetime spectra of TCPP
platinum and PCNH (b). XPS fine spectra of cis-platinum (c) and PCNH and PCNH at room temperature (c) and liquid nitrogen temperature
(d).
(d). All the excited wavelengths are 515 nm.
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PCNH were centred around 650 nm (Fig. 3a). Although the
uorescence quantum yield of PCNH (Qp) decreased to 67.8%
with TCPP as a reference under the same conditions (PBS
buffer, pH 7.24), the value of Qp was still acceptable and strong
enough for cell imaging.30 Moreover, the wavelength of uo-
rescence was situated at the edge of the near-infrared I imaging
window, which can help eliminate interference from biolumi-
nescence and decrease the absorption from surrounding
tissues.31 Additionally, when excited both at the Soret band and
Q bands for both TCPP and PCNH, a singlet oxygen uorescence
emission peak at 1276 nm will appear (Fig. S5, ESI†). Because
the lifetime of singlet oxygen is shorter than 200 ns and the
diffusion distance is no longer than 20 nm,32 ensuring appro-
priate singlet oxygen quantum yields is very crucial for PDT.
When excited by 515 nm light, although the absorbance
intensity was similar (Fig. S6, ESI†), the singlet oxygen uores-
cence intensity of PCNH was obviously stronger than that of
TCPP (Fig. 3b) and the singlet oxygen quantum yield of PCNH
was 46% higher than that of TCPP under the same conditions;
this is due to the heavy atom effect of platinum and the pro-
longed lifetime of the triplet state of the photosensitizer (Fig. 3c
and d).33 Furthermore, the photostability was also characterized
by UV-vis spectra aer exposure to natural light for 24 h. The
absorbance of TCPP decreased by 43.9%, while that of PCNH
decreased by only 11.8%; this implies that the photosensitizers
can be effectively protected when integrated into the nano-
hybrid (Fig. 4a and S7 in the ESI†). The enhancement of pho-
tostability is very crucial for practical applications because
photostability is a prerequisite for continuously producing toxic
singlet oxygen.
Fig. 5 Fluorescence images of HeLa cells (a) red channel indicating
PCNH fluorescence (a1), green channel corresponding to DCFH-DA
(a2), bright field (a3) and the merged image (a4). (b) ROS cumulative
production photographs taken by a confocal laser scanning micro-
scope with DCFH-DA as the indicator (excitation interval is 2 min).
investigated in vitro on HeLa cells at a concentration of 20 mM.
Aer cultivation for 3 h, the whole cells were lit with red uo-
rescence; this indicates that PCNH can be taken up by HeLa
cells, which is benecial for photodynamic therapy (Fig. 5a1).
Furthermore, DCFH-DA was used as a ROS sensor (Fig. 5a2). The
green uorescence of DCFH-DA coincided well with the red
uorescence of TCPP, which further shows that PCNH can act
not only as a photosensitizer but as an imaging reagent to
monitor the procedure of drug delivery (Fig. 5a4). With
increasing irradiation time, the singlet oxygen accumulated
ceaselessly, and the green uorescence became stronger
(Fig. 5b).
To verify the therapeutic effects in vitro, the MTS assay was
used on HeLa cells with an LED lamp as the irradiation source.
Because cis-platinum kills cancer cells by binding and twisting
DNA,34 light has negligible inuence on cell viability when only
cis-platinum is added (Fig. 6a and b). Because light is one of the
prerequisites for PDT, the cell viability greatly relies on light
irradiation when TCPP is added. Therefore, the viability
remains at 85% in the dark when 40 mM TCPP is added (Fig. 6a);
however, this value decreased to 47% at the same concentration
when the cells were irradiated (Fig. 6b). Meanwhile, the IC50
values for TCPP, cis-platinum, and PCNH were 35.4 ꢃ 1.2 mg
mLꢀ1, 17.2 ꢃ 1.1 mg mLꢀ1 and 6.8 ꢃ 1.1 mg mLꢀ1 with light
(Fig. S8, ESI†), respectively. The combination index obtained by
IC50 was much smaller than 1 (combination index ¼ 0.28),
which shows the great synergistic effect of chemotherapy and
As mentioned above, the formation of PCNH was based on
the coordination of TCPP4ꢀ with cis-platinum. However, the
coordination ability of TCPP4ꢀ relies on the pH value. In an acid
environment, PCNH will disassemble gradually. The percentage
of accumulatively released TCPP was quantied (Fig. 4b). Only
10% of TCPP was released when the pH value was 7.24.
However, when the pH value decreased to 5.02, 74% of the TCPP
disassembled from PCNH within 24 h. These results showed
that PCNH is relatively stable in a normal physiological envi-
ronment and can slowly disassemble in the acidic tumor
microenvironment.
Considering that the PCNH nanohybrid contained
a porphyrin emission centre, it can help monitor the procedure
of drug delivery. Fluorescence imaging of PCNH was
Fig. 4 Photostabilities of PCNH and TCPP when exposed to natural Fig. 6 Cell viability of HeLa cells after incubation with different
light for 24 h (a). Cumulative release of TCPP from PCNH in different concentrations of TCPP, cis-platinum and PCNC in the dark (a) or with
pH solutions ((b); the concentration of PCNH is 1 mg mLꢀ1).
LED ((b), total power: 20 W).
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4 Conclusions
In conclusion, a novel SDDS nanohybrid named PCNH, based
on the coordination assembly of TCPP and cis-platinum, was
designed and synthesized. Because the nanohybrid PCNH only
contains two drugs, high loading capacity can be easily realized.
Meanwhile, PCNH can effectively protect TCPP from photo-
bleaching, which is very crucial for PDT. Due to the heavy effect
of platinum ions, which were coordinated with TCPP, the
singlet oxygen quantum yield increased by 46%. Furthermore,
on the basis of the coordination assembly of the photosensitizer
TCPP, which is widely used in PDT, and cis-platinum, which is
used in chemotherapy, synergetic therapy with high efficiency
can be realized; the combination index is only 0.28. This work
may pave a new way for the design and progress of SDDs and
precise cancer treatment.
15 S. Y. Qin, A. Q. Zhang, S. X. Cheng, L. Rong and X. Z. Zhang,
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Conflicts of interest
There are no conicts to declare.
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Acknowledgements
This work was supported by the National Natural Science
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