Defect-engineered porphyrinic metal-organic framework nanoparticles for targeted multimodal cancer phototheranostics

Article abstract of DOI:10.1039/d0cc07903k

Defect-engineered porphyrinic MOF nanoparticles were fabricated with anin situone-pot protocol using cypate as the co-ligand and modulator. This multifunctional nanoplatform integrated the photothermal and multimodal imaging properties of cypate with the photodynamic effects of porphyrins, thus achieving targeted multimodal cancer phototheranostics after folic acid modification.

Full text of DOI:10.1039/d0cc07903k

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Defect-engineered porphyrinic metal–organic
framework nanoparticles for targeted multimodal
cancer phototheranostics†
Cite this: Chem. Commun., 2021,
57, 4035
Received 4th December 2020,
Accepted 17th March 2021
Chenyuan Wang,a Chuxiao Xiong,a Zhike Li,a Liefeng Hu,a Jianshuang Weib and
a
Jian Tian
*
DOI: 10.1039/d0cc07903k
rsc.li/chemcomm
Defect-engineered porphyrinic MOF nanoparticles were fabricated (FLI) has high sensitivity and rapid response of light but suffers
with an in situ one-pot protocol using cypate as the co-ligand and from limited penetration depth. Thus, the integration of PAI and
modulator. This multifunctional nanoplatform integrated the FLI could surmount the respective drawbacks and provide more
photothermal and multimodal imaging properties of cypate with comprehensive biomedical imaging information.11,12 Cypate is a
the photodynamic effects of porphyrins, thus achieving targeted dicarboxylic acid-containing carbocyanine fluorophore, which is
multimodal cancer phototheranostics after folic acid modification. used as an imaging agent for PAI, FLI and photothermal imaging
(PTI). It also exhibits high photothermal conversion efficiency for
Phototherapy, including photodynamic therapy (PDT) and PTT with concurrent PDT effects under NIR irradiation.13,14
photothermal therapy (PTT), has attracted great attention Therefore, cypate has great advantages as a phototheranostic
owing to its advantages of minimal invasion, high selectivity, agent. Nonetheless, its applications are severely limited by its
and broad-spectrum anti-tumor effects.1,2 PDT relies on photo- poor aqueous solubility and stability. To solve these issues, the
sensitizers to convert O2 into cytotoxic reactive oxygen species most common strategy is conjugating cypate onto nanocarriers to
(ROS) under light irradiation, which would cause tumor cell improve its stability and bioavailability.15,16 However, the synthetic
apoptosis and necrosis.3,4 In PTT, photothermal agents convert processes are relatively cumbersome and limited by the reactivity of
near-infrared (NIR) light into local heat energy, thereby inducing chemical bonds. This prompted us to develop a simple and
apoptosis of cancer cells by hyperthermia.5 However, it is difficult effective cypate-based phototheranostic nanoplatform.
to achieve complete tumor eradication using PDT or PTT alone.
Metal–organic frameworks (MOFs), assembled from metal
PDT is restricted by tumor hypoxia, and PTT induces thermo- ions and organic linkers, are emerging as a versatile platform
resistance of tumor cells. Nevertheless, PTT can promote PDT for biomedical applications.17,18 Recently, porphyrinic MOFs
effects by increasing the blood flow rate to improve the oxygen (pMOFs) have attracted significant research attention due to
supply to tumor tissues, and PDT further eliminates the heat- their intriguing PDT properties.19,20 Carboxylated porphyrins
resistant tumor cells in PTT.6 Therefore, the cooperation of PDT are used as organic linkers to assemble pMOFs, thereby pre-
and PTT could achieve synergistic effects for highly effective venting porphyrins from self-aggregation and improving the
tumor elimination.7
overall PDT efficacy. Porphyrinic Zr-MOFs, such as PCN-224,
Phototheranostics integrate diagnosis and therapy, which contain abundant binding sites on their constituent Zr6 clusters,19
permits light-triggered real-time imaging and concurrent in situ which provides opportunities for the carboxyl coordination of
treatment of tumors, improving the effect of phototherapy. cypate and the introduction of multimodal functionalities.
Among the existing diagnostic techniques, photoacoustic imaging
Herein, we report a simple and efficient one-pot method to
(PAI) exhibits high temporal resolution and deep penetration construct nanoscale defect-engineered porphyrin/cypate-based
depth but lacks sensitivity.8–10 Conversely, fluorescence imaging MOFs (PC-MOFs) for multimodal cancer phototheranostics
(Scheme 1).21,22 The combined properties of cypate and por-
a Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (MOE),
School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China.
E-mail: jian.tian@whu.edu.cn
b Collaborative Innovation Center for Biomedical Engineering,
Wuhan National Laboratory for Optoelectronics-Huazhong University of Science
and Technology, Wuhan, Hubei 430074, China
phyrin as dual ligands enabled the MOF nanoagent to perform
FLI/PAI/PTI trimodal imaging-guided PDT/PTT synergistic ther-
apy. In addition, folic acid (FA), a typical tumor cell-targeting
ligand, was conjugated onto the surfaces of the PC-MOFs via
coordination interactions.23,24 The obtained nanoplatform
PC-MOFs-FA could actively target tumor tissue to achieve
high-efficacy multimodal cancer phototheranostics. This work
† Electronic supplementary information (ESI) available: Experimental details,
characterization and Fig. S1–S20. See DOI: 10.1039/d0cc07903k
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The UV-visible absorption spectra of PC20-MOFs revealed the
co-existence of cypate and H2TCPP in the NPs (Fig. 1b), with a
1
cypate/H2TCPP ratio of about 1 : 6.2 as determined by H NMR
spectroscopy of dissolved NPs (Fig. S6, ESI†). Besides, the UV-
vis absorbance of the cypate moiety in both cypate-Zr4+ and
PC20-MOFs had a slight redshift compared to free cypate,
implying the formation of cypate-based coordination com-
plexes (Fig. S8, ESI†). It was also observed that the content of
cypate in PC20-MOFs remained stable after extensive dialysis,
while cypate-loaded PCN-224 NPs showed significant leaking,
implying that cypate was part of the coordination network of
PC20-MOFs instead of being encapsulated in porous channels
(Fig. S9, ESI†). The powder X-ray diffraction (PXRD) pattern of
PC20-MOFs was consistent with that of simulated PCN-224,19
indicating that it had the PCN-224-type crystal structure
(Fig. 1c). The nitrogen adsorption isotherm of PC20-MOFs
revealed the characteristics of mesopore distribution (Fig.
S10, ESI†), ascribed to the defected PCN-224 structure with
the use of cypate as the co-ligand and modulator. The BET
surface area was calculated to be about 477.1 m2 gÀ1, which was
larger than that of pristine PCN-224 NPs,25 indicating that
cypate served as the framework of PC20-MOFs rather than being
loaded into the pores. FA was then modified onto PC20-MOFs by
the coordination of its carboxyl group to the unsaturated Zr6
cluster. The absorption peak of FA was observed at 289 nm in
Scheme 1 Schematic illustration of the fabrication of the PC20-MOF-FA
nanoplatform and its application in PTI/FLI/PAI trimodal imaging-guided
PDT/PTT synergistic cancer therapy.
provides an effective strategy for assembling multiple photo-
therapeutic agents into a MOF-based multifunctional theranos-
tic platform.
A one-pot solvothermal protocol was used to construct the
dual-ligand Zr-MOF nanosystem. By varying the cypate/
tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) feeding ratio,
PCX-MOF nanoparticles (NPs) with different morphologies were
obtained (Table S1, ESI,† x represents the feed weight of
cypate). As shown in Fig. 1a and Fig. S4 and S5 (ESI†), with
the increasing content of cypate, the crystallinity of the PCX-
MOF NPs gradually decreased. When the dose of cypate
increased to 40 mg, the resulting PC40-MOF NPs became
shapeless with substantially small crystalline regions, which
was because the very high cypate/H2TCPP ratio interferes with
the crystal nucleation and growth. Considering the optimized
morphology of the NPs and the content of cypate in PCX-MOF
NPs, PC20-MOF-FA was selected for further studies.
the UV spectra, proving the successful modification of PC20
-
MOFs with FA (Fig. S11, ESI†). The hydrodynamic size and zeta
potentials of the samples before and after FA modification were
monitored by dynamic light scattering (DLS). The average
diameter of PC20-MOFs-FA increased from 127.8 nm to
153.7 nm (Fig. 1d) and the zeta potential changed from 25.0
mV to À23.2 mV (Fig. S13, ESI†). The stability of PC20-MOFs-FA
in a biological medium was further evaluated by DLS and ICP-
MS. After being incubated in DMEM or saline for 4 days, the
particle size, polydispersity index (PDI), and Zr4+ content of
PC20-MOF-FA NPs remained stable (Fig. S14, ESI†).
The photothermal effect of PC20-MOFs-FA was subsequently
assessed. As shown in Fig. 2a and Fig. S15 (ESI†), the tempera-
ture of PC20-MOF-FA aqueous dispersion increased with the
extension of 808 nm laser irradiation time, and the photother-
mal effect was concentration-dependent and laser power-
dependent. Moreover, the photothermal conversion efficiency
of PC20-MOFs-FA was calculated to be B32.2%, suggesting the
great potential of PC20-MOFs-FA for PTT applications (Fig. S16,
ESI†). In order to evaluate the ROS productivity of PC20-MOFs-
FA, 1,3-diphenylisobenzofuran (DPBF) was selected as the ROS
probe to explore the 1O2 generation. As depicted in Fig. 2b, the
DPBF absorbance at 415 nm in PC20-MOF-FA solution
decreased by 72.72% under 660 nm laser irradiation and by
36.63% under 808 nm laser irradiation, while the control
groups only showed a slight decrease. These results revealed
that the ROS generation capability of the porphyrin was much
stronger than that of cypate in PC20-MOFs-FA. To further
investigate the intracellular ROS production of PC20-MOFs-FA
under laser irradiation, DCFH-DA was selected as the fluores-
cent probe to monitor intracellular ROS levels. As illustrated in
Fig. 1 (a) TEM images of PCN-224, PC10-MOF, and PC20-MOF NPs.
(b) UV-Vis absorption spectra of cypate, H2TCPP, and PC20-MOF aqueous
dispersion. (c) PXRD patterns of simulated PCN-224, PCN-224 and
PC20-MOF NPs. (d) Number-average diameters of PC20-MOF and PC20
-
MOF-FA NPs in H2O.
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(Fig. S23, ESI†), indicating that MOFs modified with FA could
target the overexpressed folate receptor on 4T1 cells and
increase the cellular uptake. To investigate the in vitro photo-
therapy effect of PC20-MOFs-FA, MTT assays were then
employed to compare the survival rates of 4T1 cells after
different treatments. The phototherapy effect was concentration-
dependent, and a lower cell survival rate was observed for the
dual-laser treatment, which has a half-maximal inhibitory concen-
tration (IC50) of 45.9 Æ 0.3 mg mLÀ1 (Fig. S24, ESI†). Furthermore,
dead/live cell staining demonstrated the same result as MTT
assays, indicating that PC20-MOFs-FA plus the dual-laser irradia-
tion was more effective in cancer cell killing (Fig. 2c).
In vivo FLI/PAI/PTI of PC20-MOFs-FA for precise tumor
diagnosis was further explored using 4T1 tumor-bearing mice.
The FLI studies showed that the fluorescence intensity of the
tumor site gradually increased after IV injection of PC20-MOFs-FA
(15 mg kgÀ1), and the fluorescence signal reached the highest
24 h post-injection. Comparatively, only a weak fluorescence
signal could be observed at the tumor site 2 h after IV injection
of PC20-MOFs, illustrating the excellent active-targeting ability of
Fig. 2 (a) Photothermal effect of PC20-MOFs-FA under 808 nm laser
irradiation (1 W cmÀ2, 3 min) with different concentrations. (b) ROS
generation of PC20-MOFs-FA under 660 nm (0.1 W cmÀ2, 5 min)/
808 nm (1 W cmÀ2, 5 min) laser irradiation for different times. (c) Live/
dead assay of 4T1 cells after different treatments. Green fluorescence:
calcein-AM; red fluorescence: propidium iodide (PI). Scale bars = 100 mm.
Fig. S17 (ESI†), 4T1 cells treated with PC20-MOFs-FA showed PC20-MOFs-FA toward 4T1 tumors with the overexpressed folate
green fluorescence after being irradiated using a 660 nm laser receptor (Fig. 3a and b). The PA signal of PC20-MOF-FA solution
or an 808 nm laser, and the fluorescence intensity of the exhibited a linear enhancement with increasing concentration
660 nm group was stronger than that of the 808 nm group.
(Fig. S25a, ESI†), indicating its great potential for in vivo PA
Notably, the intracellular fluorescence intensity under dual imaging. Hence, we performed PAI of PC20-MOFs-FA on 4T1
808 nm and 660 nm laser irradiation was the strongest, tumor-bearing mice. After IV injection of PC20-MOFs-FA, the PA
indicating the highest intracellular ROS production. These signal intensity at the tumor site gradually increased and reached
results implied that PC20-MOFs-FA held great promise as a the highest at 24 h (Fig. S25b, ESI†), consistent with the FLI
potent PDT/PTT dual-modal therapeutic nanoagent. 3-(4,5- outcomes. Next, in vivo photothermal experiments were con-
Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) ducted 24 h after IV injection of PC20-MOFs-FA using 808 nm
and in vitro hemolysis assays were applied to assess the laser irradiation (1 W cmÀ2) for 5 min. PTI of tumor tissues was
biocompatibility of PC20-MOFs-FA. The survival rates of cells performed using a thermal imaging system and revealed that the
(L929, 4T1, HepG2, CT26) after 24 h incubation with different local temperature of the tumors increased from 35.4 1C to 56.7 1C
concentrations of PC20-MOFs-FA were greater than 90% under (Fig. S26, ESI†), suggesting the great potential of PC20-MOFs-FA
dark conditions (Fig. S18, ESI†). Besides, PC20-MOFs-FA did not for in vivo PTT applications. Altogether, the results indicated that
show any hemolysis after co-incubation with red blood cells in PC20-MOFs-FA could achieve tumor-selective delivery and FLI/PAI/
a simulated physiological environment (Fig. S19, ESI†). Healthy PTI tri-modal diagnostic imaging.
BALB/c mice were used to further evaluate the systemic toxicity
The combined PDT/PTT anticancer effect of PC20-MOFs-FA
of PC20-MOFs-FA. No obvious pathological abnormalities of was next investigated in vivo. When the tumor volume reached
major organs were observed from hematoxylin and eosin B80 mm3, 4T1 tumor-bearing mice were randomly divided into
(H&E) stained images for the mice 14 days after intravenous six groups receiving different treatments. According to the
(IV) injection of PC20-MOFs-FA (Fig. S20, ESI†). Furthermore, results of FLI/PAI/PTI tri-modal imaging, the corresponding
the serum biochemical indicators of the treatment group laser radiation was applied to the tumor site 24 h post-
showed no significant difference from the control group injection. The tumor volumes of the mice were recorded every
(Fig. S21, ESI†), suggesting the excellent biocompatibility and
biosafety of PC20-MOFs-FA.
To study the uptake of PC20-MOFs-FA into 4T1 cells, the
intracellular fluorescence intensity was monitored by confocal
laser scanning microscopy (CLSM) after incubation with
PC20-MOFs-FA (100 mg mLÀ1) for different hours. After 8 h of
incubation, the intracellular fluorescence intensity became the
strongest (Fig. S22, ESI†). Therefore, 8 h was selected for the
co-incubation time with 4T1 cells for subsequent experiments.
In addition, PC20-MOFs-FA and PC20-MOFs were incubated with
Fig. 3 In vivo fluorescence imaging. (a) Near-infrared (NIR) fluorescence
images and (b) NIR signal intensity changes in 4T1 tumor-bearing mice
4T1 cells for 8 h and the cellular uptake of PC20-MOFs-FA
exceeded that of PC20-MOFs under the same conditions
before and after IV injection of PC20-MOF and PC20-MOF-FA NPs. White
circles indicate tumor sites.
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one multivariate MOF for synergistic effects, opening up new
perspectives in the development of versatile nanoplatforms for
cancer theranostics.
This work was financially supported by the National Natural
Science Foundation of China (NSFC) (No. 21601140 and
21871214) and the Fundamental Research Funds for the
Central Universities (2042017kf0186).
Conflicts of interest
There are no conflicts to declare.
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