Thermal Stimuli-Triggered Drug Release from a Biocompatible Porous Metal–Organic Framework

Article abstract of DOI:10.1002/chem.201701904

Drug delivery carriers with a high drug loading capacity and biocompatibility, especially for controlled drug release, are urgently needed due to the side effects and frequently dose in the traditional therapeutic method. In our work, a Zr-based metal–organic framework named ZJU-801, which is isoreticular with NU-801, has been designed and further demonstrated as an excellent drug delivery system (DDS) with a high drug loading of 41.7 %. Such a high drug loading capacity may be ascribed to the appropriate match of the size and the large pore volume of this kind of Zr MOF material. Compared with DS@NU-801, this DDS has successfully achieved on-command heating-activated drug release, which was probably attributed to the bulkier ligand, the better stability, and the intense π–π interaction between ZJU-801 and diclofenac sodium (DS) demonstrated comprehensively by SEM, powder X-ray diffraction (PXRD), FTIR and ¹³C solid-state NMR spectroscopy as well as computer simulations. It is worth noting that premature drug release was avoided effectively without any complicated post-modifications. The low cytotoxicity and good biocompatibility of our DDS were certificated by the in vitro favorable results from an MTT assay, a WST-1 assay, and confocal microscopy imaging.

Full text of DOI:10.1002/chem.201701904

DOI: 10.1002/chem.201701904
Full Paper
&
Drug Delivery
Thermal Stimuli-Triggered Drug Release from a Biocompatible
Porous Metal–Organic Framework
Ke Jiang+,[a] Ling Zhang+,[a] Quan Hu,[b] Qi Zhang,[a] Wenxin Lin,[a] Yuanjing Cui,*[a] Yu Yang,[a]
and Guodong Qian*[a]
Abstract: Drug delivery carriers with a high drug loading ca-
pacity and biocompatibility, especially for controlled drug re-
lease, are urgently needed due to the side effects and fre-
quently dose in the traditional therapeutic method. In our
work, a Zr-based metal–organic framework named ZJU-801,
which is isoreticular with NU-801, has been designed and
further demonstrated as an excellent drug delivery system
(DDS) with a high drug loading of 41.7%. Such a high drug
loading capacity may be ascribed to the appropriate match
of the size and the large pore volume of this kind of Zr MOF
material. Compared with DS@NU-801, this DDS has success-
fully achieved on-command heating-activated drug release,
which was probably attributed to the bulkier ligand, the
better stability, and the intense p–p interaction between
ZJU-801 and diclofenac sodium (DS) demonstrated compre-
hensively by SEM, powder X-ray diffraction (PXRD), FTIR and
13C solid-state NMR spectroscopy as well as computer simu-
lations. It is worth noting that premature drug release was
avoided effectively without any complicated post-modifica-
tions. The low cytotoxicity and good biocompatibility of our
DDS were certificated by the in vitro favorable results from
an MTT assay, a WST-1 assay, and confocal microscopy imag-
ing.
Introduction
a high drug capacity and a controllable release ability still re-
mains to be challenging.
Drugs are extensively used as bioactive compounds to cure ill-
ness and even kill stubborn cancer cells. However, the thera-
peutic efficacy of drugs has to be discounted drastically due to
their poor solubility, burst release, short circulation, and non-
selective biodistribution.[1] With the fast development of nano-
technology, plenty of nanoscale drug delivery systems includ-
ing polymer–protein conjugates, liposomes, carbon nanotubes,
dendrimers, and mesoporous silica nanoparticles[2] were de-
signed and synthesized to overcome the aforementioned
problems. Nevertheless, these proposed routes also suffer from
differently fatal limitations, such as degradation resistance for
inorganic platforms, low drug capacity for polymers, and inad-
equate control of drug release for organic platforms.[3] In this
regard, developing a drug delivery system (DDS) with both
Recently, metal–organic frameworks (MOFs), a series of novel
porous crystal materials self-assembled from different metal
ions or clusters and organic linkers, have received much atten-
tion for various applications, such as gas sorption and separa-
tion,[4] catalysis,[5] and sensing.[6] Especially, MOFs have an ex-
hibited high potential as favorite drug carrier by the virtue of
their irresistible advantages, such as ultra-high surface areas,
tunable functionalities, designable host–guest interaction, and
multiple topologies.[7] With these in mind, the elaboration of
MOFs with high drug loading capacity and temperature re-
sponsiveness is of benefit for thermal stimuli-triggered drug re-
lease.
Many researches have reported in succession about the per-
formance of MOFs[8] at drug release. Yang et al. reported a pH-
controlled drug delivery system based on UMCM-1-NH2
capped by a carboxylatopillar[5]arene supramolecule. Yang
and co-workers also successfully realized the double response
of the Zn2+ triggering and the thermal-activated drug release
by using the above-mentioned method with UiO-66-NH2.[9] Ap-
parently, these two groups have successfully achieved the con-
trol of drug release in spite the drug loading capacity is not
mentioned. However, the procedure of the post-modification
was tedious and it still needed to be improved. First, the po-
rosity of the MOFs had to be reduced due to the grafted sub-
stance, thus reducing the drug loading capacity. Second, the
unnecessary leak of drugs was very likely to be caused during
the tedious procedures. Third, the long-winded steps certainly
increased the unfavorable cost as for practical applications.
[a] K. Jiang,+ L. Zhang,+ Q. Zhang, W. Lin, Prof. Dr. Y. Cui, Dr. Y. Yang,
Prof. Dr. G. Qian
State Key Laboratory of Silicon Materials
Cyrus Tang Center for Sensor Materials and Applications
School of Materials Science and Engineering, Zhejiang University
Hangzhou, 310027 (P. R. China)
E-mail: cuiyj@zju.edu.cn
gdqian@zju.edu.cn
[b] Prof. Q. Hu
Department of Pharmacology, School of Medicine
Hangzhou Normal University, Hangzhou 310036 (P. R. China)
[+] These authors contributed equally to this work.
Supporting information for this article can be found under:
https://doi.org/10.1002/chem.201701904.
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Herein, an organic ligand, namely, (2E,2’E)-3,3’-(naphthalene-
1,4-diyl)diacrylic acid (H2NPDA), was designed and thus a Zr-
based MOF named ZJU-801 (ZJU=Zhejiang University) isoretic-
ular with NU-801 was synthesized.[11] ZJU-801 was further dem-
onstrated to be an excellent drug delivery system, which suc-
cessfully encapsulates the model drug diclofenac sodium (DS)
with a high loading capacity of 41.7%. The naphthalene
moiety was introduced into the ligand in order to augment
the interaction between the framework and the drug so that
the premature release was avoided effectively and thus weak-
ening the side effects to normal tissues. As expected, the DDS
realized the thermal stimuli-triggered drug release without any
tedious post-synthetic modifications, the premature releases at
25 and 378C were negligible and the drug releases obviously
accelerated up to 45 and 608C. Besides the high drug loading
capacity and the significantly heat-activated drug delivery, the
low cytotoxicity of our DDS was double checked according to
the in vitro results from a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphe-
nyltetrazolium bromide (MTT) assay and a WST-1 (WST=water
soluble tetrazolium) assay, and the good biocompatibility was
visualized through confocal microscopy images and favorable
sizes from SEM and TEM images.
Figure 2. Construction of the framework of ZJU-801. a) The two-coordination
ligand H2NPDA for ZJU-801. b) The twelve-coordination secondary building
units (SBUs) Zr6O4(OH)4(CO2)12 of the framework. c) The smaller tetrahedral
cage with a diameter of about 10.0 ꢁ constructed from four SBUs and six li-
gands. d) The larger octahedral cage with a diameter of about 13.6 ꢁ com-
posed of six SBUs and twelve ligands (C=dark gray, O=red, Zr=light gray,
hydrogen atoms are omitted for clarity).
Results and Discussion
al.[12] The two-coordination ligand H2NPDA (Figure 2a), as the
prolongation of the classical ligand H2BDC, is connected with
the twelve-coordination secondary building units (SBUs)
Zr6O4(OH)4(CO2)12 (Figure 2b) to construct the 3D framework.
Moreover, there exist two distinct polyhedral cages. The larger
octahedral cage is composed of six SBUs and twelve ligands
with a diameter of approximately 13.6 ꢁ and the smaller tetra-
hedral cage of about 10.0 ꢁ is constructed from four SBUs and
six ligands. Apparently, the sufficient pore volume and the
robust framework offer the bright potential for further charac-
terization.
The organic linker (2E,2’E)-3,3’-(naphthalene-1,4-diyl)diacrylic
acid (H2NPDA) was synthesized through Heck cross-coupling
reactions on the basis of the previously reported work.[10] 1,4-
Dibromonaphthalene reacted with ethyl acrylate, followed by
hydrolysis, acidification, and drying off. The solvothermal reac-
tion of ZrOCl2·8H2O and H2NPDA with the addition of a small
amount of formic acid afforded ZJU-801 as a yellow powder
and the favorable adoption of formic acid guaranteed the high
quality of the crystals.
The powder purity of ZJU-801 was further confirmed by
powder X-ray diffraction analysis (PXRD), which demonstrated
that ZJU-801 is isoreticular with NU-801 (Figure 1), first synthe-
sized and characterized by Farha et al.[11] As illustrated in
Figure 2, ZJU-801 has the novel fcu topology, the same as the
UiO series, which demonstrates the robustness of the materi-
After an acetone-exchange reaction, ZJU-801 was evacuated
at 333 K for 12 h and at 373 K for 2 h under high vacuum to
evaluate the permanent porosity of ZJU-801. Subsequently, the
permanent porosity of activated MOF ZJU-801a was estimated
by N2 adsorption at 77 K. The of N2 sorption isotherms at 77 K
demonstrated type-I adsorption characteristic for ZJU-801a.
The saturation of the N2 sorption isotherms at 77 K attained
420.7 cm3 gÀ1 (Figure S3 in the Supporting Information), to-
gether with
a
pore volume of 0.64 cm3 gÀ1. Thus, the
Brunauer–Emmett–Teller (BET) surface of ZJU-801a was esti-
mated to be 1140 m2 gÀ1.
Diclofenac sodium (DS), one of the most useful non-steroidal
anti-inflammatory drug (NSAIDs) agents, was chosen as
a model drug for a subsequently controllable release due to its
short half-period and hydrophilic character. In most cases, or-
ganic solvents including methanol[13a] and ethanol,[13b] were
employed as drug loading solvents on account of the limita-
tive stability of the MOFs, which could do harm to the biologi-
cal tissues more or less whereas deionized water was selected
for encapsulating DS during our work based on the suitable
stability of ZJU-801. The DS loading procedure was carried out
in deionized water at room temperature with gently stirring
Figure 1. Powder X-ray diffraction patterns of the as-synthesized NU-801,
ZJU-801, and DS@ZJU-801 along with the simulated NU-801.
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for twelve hours. ZJU-801 after DS loading was termed
DS@ZJU-801 and the crystallinity of ZJU-801 before and after
the drug loading was remained evidenced by PXRD (Figure 1).
Furthermore, SEM and TEM were applied to characterizing the
morphology of ZJU-801 before and after drug encapsulating.
There is almost no influence on the regular octahedron mor-
phology of ZJU-801 after drug loading (Figure 3) and the aver-
Figure 3. a) SEM image of ZJU-801. b) SEM image of DS-loaded ZJU-801.
c) TEM image of ZJU-801. d) TEM image of DS-loaded ZJU-801.
Figure 4. a) DS released from ZJU-801 in PBS at 25, 37, 45, and 608C. b) DS
released from NU-801 in PBS at 25, 37, and 608C.
age sizes of ZJU-801 and DS@ZJU-801 are around 200 nm,
which is favorable for good biocompatibility and uptake for
cells. The diameter of the DS is approximately 10 ꢁ, matching
well with the framework of ZJU-801 together with the suitable
pore volume of ZJU-801 that is very likely to contribute to the
high drug loading capacity. As was expected, ZJU-801 exhibit-
ed an outstanding drug loading capacity of approximately
41.7 wt%, calculated from 1H NMR spectra (Figure S7 in the
Supporting Information) and thermogravimetric analysis (TGA;
Figure S9 in the Supporting Information), which is higher than
those of plenty of famous MOFs, such as bio-mof-
1 (22 wt%)[14a] and Fe-MOF-74 (16 wt%).[14b]
nificance for the transport of the nanoparticle to cancer tis-
sue.[15a] Hence, the nanoscale ZJU-801 could accumulate in
tumor sites through an enhanced permeation and retention
(EPR) effect.[15b] Thus the release mainly occurred in the local
hyperthermia tissues or organs. Combined with chemotherapy,
the synergetic therapy method could be more effective. In-
spired by the interesting phenomenon, the kinetic profiles of
the drug delivery from NU-801 encapsulating DS in PBS
(pH 7.4) at 25, 37, and 608C further demonstrated the delivery
mechanism of DS@ZJU-801. Markedly, there are absolutely dif-
ferent behaviors between DS@ZJU-801 and DS@NU-801 (Fig-
ure 4b). The burst release phenomena were discovered in
DS@NU-801 for all three temperatures. What is more, more
than 70% cumulative drug release was detected within five
hours at 378C.
Why is there a stimuli-triggered phenomenon for the drug
release of ZJU-801? The totally different behaviors of DS@ZJU-
801 and DS@NU-801 have given an effective proof to specu-
late on the significance of the naphthalene group. Apparently,
the ligand of ZJU-801 is bulkier than that of NU-801, thus slow-
ing down the diffusion of DS within the framework of ZJU-801.
Apart from the simple bulk comparison of the different ligands,
it is reasonable enough to speculate that the naphthalene
groups inside the framework of ZJU-801 play a key role in en-
hancing the interaction between the drug and the framework.
Herein, Fourier transform infrared (FTIR) spectroscopy was em-
As shown in Figure 4a, the sustained drug delivery profiles
were obtained from DS@ZJU-801 lasting 24 h monitored by
HPLC in phosphate-buffered saline (PBS; pH 7.4) at 25, 37, 45,
and 608C. Interestingly, there is a significantly heat-activated
drug delivery phenomenon. The premature releases at 25 and
378C were negligible, whereas the DS release was apparently
accelerated when the temperature ascended to 458C, and es-
pecially to 608C. The release rate of 608C was approximately
3.4 times higher than that at 378C and almost 10.3 times
higher than that at 258C. The higher the temperature, the
quicker the release of the cargo. Obviously, ZJU-801 can be an
excellent candidate for thermal stimuli-triggered drug release,
which will bring inappreciable injury to normal tissues. What is
more, the characteristic of all tumors including leaky neovascu-
latures and ineffective lymphatic drainage, causes an enhanced
permeability and retention (EPR) effect. The EPR effect is of sig-
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tween the organic linker of ZJU-801 and the drug DS is strong
enough to enhance tremendously the interaction between the
framework and DS„ which contribute to the thermal stimuli-
triggered drug delivery of ZJU-801 without any post-modifica-
tion. Apart from the bulkier ligand and the intense p–p conju-
gation of DS@ZJU-801, the different stability of ZJU-801 and
NU-801 is PBS has sparked another new view on the reason-
able explanation about the discrepant release behavior. As il-
lustrated in Figures S13 and S14 in the Supporting Information
showing the characterization by SEM and PXRD, the stability of
ZJU-801 is better than that of NU-801. Apparently, ZJU-801
could maintain the initial morphology at 25 and 378C and col-
lapsed partly at 608C whereas a partial collapse of NU-801 oc-
curred at 25, 37, and 608C. Compared with NU-801, it is clear
to see that the introduction of naphthalene to some extent
has attributed to the robustness of ZJU-801. However, decom-
position actually occurred in both MOFs with time, further fea-
turing the biodegradation of ZJU-801.
Based on the above-described results, ZJU-801 has a great
potential as drug delivery system with thermal stimuli-trig-
gered release. Furthermore, the cytotoxicity and biocompatibil-
ity have already verified the significance of ZJU-801 as for the
more rigorous standard. In order to evaluate the cytotoxicity of
ZJU-801, an MTT assay was employed through incubating with
PC12 cells. PC12 cells (neuron cell line from Rattus norvegicus)
are widely used in the MTT assay due to their adhesion to cul-
ture plates. Consequently, PC12 cells were chosen to assess
the cytotoxicity of nanomaterials.[17] Furthermore, the MTT
assay depends on the change from MTT to formazan caused
by the mitochondria of living cells and the transformation
from MTT to formazan implies the metabolism decrease of the
mitochondria. Hence, the number of viable cells is correlated
to the absorbance of formazan. As depicted in Figure 6a, the
cell viability was above 90% even if the concentration of ZJU-
801 was as high as 200 mgmLÀ1 indicating the negligible cyto-
toxicity of ZJU-801. Apart from MTT, the WST-1 assay was se-
lected for double checking; the obtained result was consistent
with that of the MTT assay (Figure 6b).
Figure 5. FTIR spectra of: a) NU-801, NU-801 after drug loading, and NU-801
after drug release in PBS solution for 12 h. b) FTIR spectra of ZJU-801, ZJU-
801 after drug loading, and ZJU-801 after drug release in PBS solution for
12 h.
ployed to investigate theoretically the vibrational properties of
ZJU-801 before and after DS encapsulating, to further confirm
the microscopic mechanism of the host–guest interaction. As
shown in Figure 5, the band of ZJU-801 at n˜ =1658 cmÀ1 as-
signed to n(C=C) from the double bond drifted to n˜ =
1635 cmÀ1 after drug loading and the band of ZJU-801 at n˜ =
1555 cmÀ1 assigned to n(C=C) from naphthalene drifted to n˜ =
1538 cmÀ1 after drug release after 12 h. Such red-shifted band
in the FTIR spectrum reflected an intense p–p conjugation.[16]
On the contrary, there are no changes occurring in NU-801. Be-
sides the analysis of the Fourier transform infrared spectra, 13C
solid-state NMR spectra and computer simulations were further
adopted to demonstrate the intense p–p conjugation between
the DS and ZJU-801. According to Figure S10 in the Supporting
Information, after drug loading, the peaks of ZJU-801 at d=
131.8 and 125.1 ppm assigned to naphthalene have drifted to
d=130.9 and 124.5 ppm, respectively. Such drift in the 13C
solid-state NMR spectrum reflected an intense p–p conjugation
as well. Furthermore, computer simulations were also selected
to strengthen the aforementioned argument. The energy of
DS@ZJU-801 was determined to be 197.50 kcalmolÀ1 (Fig-
ure S11c in the Supporting Information) lower than the sum of
the individual compounds ZJU-801 and DS, which testified an
energy reduction of the DDS after drug loading, thus demon-
strating an intense p–p conjugation between ZJU-801 and DS.
Herein, it is clear to understand that the p–p conjugation be-
To explore the visualization of the cytotoxicity as well as the
biocompatibility, confocal imaging was further carried out rely-
ing on the enriched neurites of PC12 neuron cells. The mor-
phology of PC12 neuron cells represents the state of viability
and the microtubular cytoskeleton and the nuclei were stained
red and blue by using b-tubulin and 4’,6-diamidino-2-phenylin-
dole (DAPI), respectively, which were easily visualized through
confocal microscopy. Two samples of ZJU-801 with concentra-
tions of 5 and 50 mgmLÀ1 were incubated with PC12 cells for
24 h. As shown in Figure 7, the appreciable neuritis extension
of PC12 cells convincingly indicated the good biocompatibility
and negligible cytotoxicity of ZJU-801. Overall, the low cyto-
toxicity and good biocompatibility permitted ZJU-801 to be an
excellent nanocontainer for a heat-triggered drug release.
Conclusions
In summary, a new organic ligand has been designed and
thus, its first MOF, that is, an isoreticular Zr-cluster-based
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of DS within the framework, strengthened the robustness of
ZJU-801, and enhanced the interaction between the frame-
work and DS so that DS@ZJU-801 exhibits a thermal stimuli-
triggered drug delivery. Furthermore, the simple and conve-
nient method without any post-modification makes ZJU-801
another non-negligible preponderance. Meanwhile, the negligi-
ble cytotoxicity and good biocompatibility of ZJU-801 were
further demonstrated by in vitro studies, including MTT and
WST-1 assays as well as confocal imaging. Overall, it is conceiv-
able that this biocompatible DDS could be a potential candi-
date in anti-inflammatory or antitumor therapy.
Experimental Section
Materials
All starting materials were obtained from commercial resources
without any purification including 1,4-dibromonaphthalene, ethyl
acrylate, palladium diacetate (Pd(OAc)2), and tetrabutylammonium
bromide (TBAB). (from Alfa Aesar) ZrOCl2·8H2O was purchased
from Aladdin. Phosphate buffered saline (PBS) was obtained from
Beijing Chem. Co. Ltd. Sodium hydroxide, hydrochloric acid, formic
acid, chloroform, dioxane, and dimethyl formamide were obtained
from Sinopharm Chemical Reagent Co., Ltd. 3-(4,5-Dimethylthiazol-
2-yl-2,5-diphenyl tetrazolium bromide (MTT), 4’,6-diamidino-2-phe-
nylindole (DAPI), and b-tubulin were purchased from Sigma–Al-
drich Co. Dulbecco’s modified eagle medium (DMEM, Neuronbc),
fetal bovine serum (FBS), penicillin/streptomycin (P/S, Boster), and
Triton X-100 were obtained from Gibco Invitrogen. Diclofenac
sodium (DS) was purchased from TCI. All other reagents were of
analytical grade from a periodical chemical company.
Figure 6. a) Results of the MTT assay of ZJU-801 incubated with PC12 cells
for 24 h. b) Results of the WST-1 assay of ZJU-801 incubated with PC12 cells
for 24 h.
Synthesis and characterization
Synthesis of (2E,2’E)-3,3’-(naphthalene-1,4-diyl)diacrylic acid
(H2NPDA): (2E,2’E)-3,3’-(Naphthalene-1,4-diyl)diacrylic acid was syn-
thesized by employing the procedure represented in Scheme S1 in
the Supporting Information. 1,4-Dibromonaphthalene (11 g,
38.46 mmol), ethyl acrylate (9 mL, 84.6 mmol), K2CO3 (6.63 g,
48 mmol), tetrabutyl ammonium bromide (TBAB; 2.06 g, 6.4 mmol),
Pd(OAc)2 (0.2 g, 0.82 mmol), and DMF (100 mL) were successively
added in a 250 mL round-bottomed flask. After the mixture was
rigorously stirred at 1308C for 24 h, it was extracted with chloro-
form and water three times. The combined organic phases were
dried over anhydrous MgSO4 while the organic solvent was dis-
tilled under reduced pressure. The residue was subjected to
column chromatography (petroleum/ethyl acetate 5:1 v/v) for fur-
ther purifying to get the diethyl 3,3’-(naphthalene-1,4-diyl)(2E,2’E)-
diacrylate. Yield: 6.6 g (60%). The purified product (3 g, 9.26 mmol)
was then suspended in a mixture of 1,4-dioxane (20 mL) and
a 10m aqueous solution of NaOH (100 mL). The mixture was rigor-
ously stirred and heated to reflux overnight, then dilute HCl was
added to the above-mentioned solution until the pH value was ad-
justed to 3. The solid was collected by filtration, washed with
water for several times until the pH value attained to neutral
before drying at 658C to obtain a yellow powder. Yield: 2.7 g
(90%); 1H NMR (500 MHz, DMSO): d=8.17 (d, J=13 Hz, 2H), 8.04
(s, 2H), 7.78 (s, 2H), 7.52 (s, 2H), 6.44 ppm (d, J=13 Hz, 2H).
Figure 7. Confocal microscopy images of PC12 cells incubated with ZJU-801
with concentrations of 5 mgmLÀ1 (a1, a2, and a3) and 50 mgmLÀ1 (b1, b2,
and b3) for 24 h. The nuclei (blue) and the microtubular cytoskeleton (red)
were fluorescently stained by DAPI and tubulin, respectively. Scale
bar=20 mm.
metal–organic framework named ZJU-801, has been synthe-
sized successfully. ZJU-801 appears to be an excellent drug car-
rier with a high drug capacity of approximately 41.7 wt%,
which could drastically lessen the dosing times. Compared
with the already known MOF NU-801, it is reasonable to specu-
late that the bulkier organic linkers have slowed the diffusion
Synthesis of (2E,2’E)-3,3’-(1,4-phenylene)diacrylic acid (H2PDA):
1,4-Dibromobenzene (9.44 g,40 mmol), ethyl acrylate (9 mL,
84.6 mmol), K2CO3 (10.35 g, 75 mmol), Pd(OAc)2 (0.561 g,
2.5 mmol), and DMF (100 mL) were mixed in a 250 mL round-bot-
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tomed flask. The mixture was stirring for 24 h at 1308C. Then, it
was extracted with ethyl acetate and water for several times. The
organic phases were combined and dried over anhydrous MgSO4
while the organic solvent was distilled under reduced pressure.
After that, the mixture was subjected to column chromatography
(petroleum/ethyl acetate 4:1 v/v) to obtain the white powder di-
ethyl 3,3’-(1,4-phenylene)(2E,2’E)-diacrylate. Yield: 6 g (64%). The
white powder (4 g, 14.6 mmol) was suspended in a mixture of THF
(20 mL), H2O (50 mL), and a 10m aqueous solution of NaOH
(100 mL). The mixture was stirred and heated to reflux for 12 h,
then THF was removed under reduced pressure. Finally, the pH
value of the solution was adjusted to three by using dilute HCl.
The solid was collected by filtration, washed with water, and dried
In vitro drug delivery
The DS delivery assays was carried out in PBS (pH 7.4) with differ-
ent temperatures including 25, 37, and 608C. A sample of the DS-
loaded ZJU-801 or NU-801 (10 mg) was suspended in PBS solution
(20 mL). The PBS was replaced with fresh PBS at particular time in-
tervals, and the amount of drug release in the delivery medium
was analyzed by high performance liquid chromatography by
using an Agilent 1200 chromatographic system. A Zorbax eclipse
XDB-C 18 reverse-phase column (5 m, 4.6 mm* 250 mm) was em-
ployed. The mobile phase consisted of 20% phosphoric acid and
40% distilled water in methanol. The effluent was monitored at
l=264 nm with a flow rate of 1.0 mLminÀ1 and an injection
volume of 25 mL. The adsorption peak for DS was observed at
around t=7.6 min.
1
to obtain a white powder. Yield: 3.5 g (87.5%); H NMR (500 MHz,
DMSO): d=7.71 (s, 4H), 7.58 (d, J=13.5 Hz, 2H), 6.58 ppm (d, J=
13.5 Hz, 2H).
Synthesis of ZJU-801: ZrOCl2·8H2O (60 mg, 0.186 mmol) of was
dissolved in DMF (5 mL) as main solvent and formic acid (0.2 mL)
was added as regulator in a screw-capped vial (15 mL) under 5 min
sonication. The ligand H2NPDA (54 mg, 0.201 mmol) was then
added and the mixture was heated to 708C for 96 h. The resulting
crystals were collected by decanting the solvent after centrifuga-
tion (10000 rpm, 15 min) for three times with DMF and acetone,
respectively.
Cell culture, imaging, and in vitro cytotoxicity assay
Rat pheochromocytoma (PC12) cells were incubated in a humidified
incubator (378C, 5% CO2) for three days employing Dulbecco’s
modified eagle medium (DMEM, Neuronbc) with 10% fetal bovine
serum (FBS), and 1% penicillin/streptomycin (P/S, Boster). The cyto-
toxicity of ZJU-801 was evaluated through standard MTT and WST-
1 assays in 96-well plates to assess the viability of PC12 cultured
cells, respectively. ZJU-801 at various concentrations (5, 50, 100,
150, or 200 mgmLÀ1) was incubated with PC12 cells for 24 h. After
that, 1ꢂMTT solution was added to each well and they were incu-
bated for another 4 h. An aliquot of the supernatant (200 mL) was
removed and dimethyl sulfoxide (150 mL) was added to the wells.
The absorbance of each well was monitored at l=490 nm through
a microplate reader. The assays were repeated six times and the
data were averaged. The procedure of the WST-1 assay was similar
to the one of the MTT assay. After incubation, WST-1 (10 mL) was
added to the wells and they were incubated for another 2 h. The
absorbance of each well was monitored at l=450 nm. The assays
were repeated six times and the data were averaged. Besides, the
Synthesis of NU-801: A mixture of the organic linker H2PDA
(45 mg, 0.21 mmol) and ZrOCl2·8H2O (60 mg, 0.186 mmol) was dis-
solved in DMF (5 mL) as main solvent and formic acid (0.22 mL)
was added as regulator in a screw-capped vial (15 mL) under
15 min sonication. The mixture was heated to 708C for 120 h. The
product was washed with DMF and acetone for three times, and
collected by decanting the solvent after centrifugation
(10000 rpm, 15 min).
Measuring the porosity of ZJU-801
In order to remove the solvent molecules inside the pores of the
framework, a sample of the as-synthesized ZJU-801 (120 mg) was
guest-exchanged with dry acetone for about ten times, then the
sample was degassed at 333 K for 12 h and at 373 K for 2 h under
high vacuum to obtain the activated ZJU-801. The sorption mea-
surement was developed with liquid nitrogen at 77 K. The whole
measurement was taken on a micromeritics ASAP 2460 surface
area analyzer.
PC12 cells were seeded with ZJU-801 (5 mgmLÀ1 and 50 mgmLÀ1
)
in a 24-well plate with a coverslip at each well incubated for 24 h.
Each well was washed three times by using 1ꢂPBS and fixed by
using 4% paraformaldehyde for 15 min. Apart from that, the PC12
cells were permeabilized through triton X-100 at room temperature
for about 2 h and blocked by bovine serum albumin (BSA) and FBS
for another 2 h. Then Alexa-fluor 647-conjugated b-tubulin (1:500
in PBS) was employed to visualize filamentous tubulin for 2 h, fol-
lowed by DAPI (5 mgmLÀ1) staining for 15 min to visualize nuclear
DNA. Fluorescence images of the cells were obtained by using
a confocal laser scanning microscope in a two-channel mode with
a laser excitation wavelength of l=633 nm for Alexa-fluor 647-
conjugated b-tubulin and l=405 nm for DAPI.
Encapsulating DS in ZJU-801 or NU-801
DS (80 mg) was dissolved in deionized water (10 mL). The as-syn-
thesized dried ZJU-801 or NU-801 (40 mg) was dispersed in the ob-
tained solution. After stirring for 12 h, the nanoparticles were col-
lected by centrifugation (5000 rpm, 10 min) and washed three
times with water to get rid of the drug on the surface of ZJU-801
or NU-801. The sediment was dried in vacuum for 1H NMR and
FTIR spectroscopy as well as other tests were performed with the
obtained products.
Characterization
Powder X-ray diffraction (PXRD) analysis was carried out on a Shi-
madzu XRD7000 powder X-ray diffractometer in the 2q=3–508
range with a recording rate of 58minÀ1 at room temperature. Scan-
ning electron microscopy (SEM) was performed by using a Hitachi
S-4800 field emission scanning electron microscope. Transmission
electron microscopy (TEM) was performed on a Philips CM200 with
Measurement of the drug loading capacity
To calculate the DS loading capacity, aliquots of ZJU-801, DS@ZJU-
801 and DS (ꢀ3 mg) were dried under vacuum at 808C overnight
and digested in [D6]DMSO (500 mL) with D2SO4 (50 mL) under soni-
cation. The DS loading capacity of ZJU-801 was quantified by
1H NMR spectroscopy at 600 MHz. The molar ratio of the organic
ligand to DS was 2:1 through calculating the peak areas of the
peaks at d=8.2 (organic ligand) and 3.5 ppm (drug).
1
an acceleration voltage of 160 kV. H nuclear magnetic resonance
(1H NMR) spectra were measured on
a Bruker Avance DMX
600 MHz spectrometer with tetramethylsilane (TMS) as internal
standard. Fourier transform infrared spectroscopy (FTIR) was per-
formed by using a Thermo Fisher Nicolet iS10 spectrometer with
KBr pallets. The 77 K N2 adsorption isotherms were recorded on an
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Full Paper
8259–8262; d) D. Zhao, X. T. Rao, J. C. Yu, Y. J. Cui, Y. Yang, G. D. Qian,
Inorg. Chem. 2015, 54, 11193–11199; e) D. Zhao, Y. J. Cui, Y. Yang, G. D.
Qian, CrystEngComm 2016, 18, 3746–3759; f) Y. J. Cui, B. L. Chen, G. D.
Qian, Coord. Chem. Rev. 2014, 273, 76–86; g) Y. J. Cui, W. F. Zou, R. J.
Song, J. C. Yu, W. Q. Zhang, Y. Yang, G. D. Qian, Chem. Commun. 2014,
50, 719–721; h) Y. J. Cui, F. L. Zhu, B. L. Chen, G. D. Qian, Chem.
Commun. 2015, 51, 7420; i) Y. J. Cui, B. Li, H. J. He, W. Zhou, B. L. Chen,
G. D. Qian, Acc. Chem. Res. 2016, 49, 483–493.
ASAP (accelerated surface area and porosimetry) 2460 system. The
drug delivery profiles were obtained by using high performance
liquid chromatography (HPLC) employing an Agilent 1200 chroma-
tographic system. Confocal microscopy imaging was performed on
a FV-1000 confocal laser scanning microscope.
Acknowledgements
[7] a) L. N. Duan, Q. Q. Dang, C. Y. Han, X. M. Zhang, Dalton Trans. 2015, 44,
1800–1804; b) M. Nazari, M. Rubio-Martinez, G. Tobias, J. P. Barrio, R. Ba-
barao, F. Nazari, K. Konstas, B. W. Muir, S. F. Collins, A. J. Hill, M. C. Duke,
M. R. Hill, Adv. Funct. Mater. 2016, 26, 3244–3249; c) W. Cai, C. C. Chu,
G. Liu, Y. X. J. Wang, Small 2015, 11, 4806–4822; d) D. D. Wang, J. J.
Zhou, R. H. Chen, R. H. Shi, G. Z. Zhao, G. L. Xia, R. Li, Z. B. Liu, J. Tian,
H. J. Wang, Z. Guo, H. B. Wang, Q. W. Chen, Biomaterials 2016, 100, 27–
40; e) H. X. Zhao, Q. Zou, S. K. Sun, C. S. Yu, X. J. Zhang, R. J. Li, Y. Y. Fu,
Chem. Sci. 2016, 7, 5294–5301; f) F. Ke, Y. P. Yuan, L. G. Qiu, Y. H. Shen,
A. J. Xie, J. F. Zhu, X. Y. Tian, L. D. Zhang, J. Mater. Chem. 2011, 21,
3843–3848; g) P. Horcajada, T. Chalati, C. Serre, B. Gillet, C. Sebrie, T.
Baati, J. F. Eubank, D. Heurtaux, P. Clayette, C. Kreuz, J. S. Chang, Y. K.
Hwang, V. Marsaud, P. N. Bories, L. Cynober, S. Gil, G. Ferey, P. Couvreur,
R. Gref, Nat. Mater. 2010, 9, 172–178; h) T. Kundu, S. Mitra, P. Patra, A.
Goswami, D. Diaz Diaz, R. Banerjee, Chem. Eur. J. 2014, 20, 10514–
10518; i) H. Oh, T. Li, J. An, Chem. Eur. J. 2015, 21, 17010–17015; j) Y.
Wang, J. Yang, Y. Y. Liu, J. F. Ma, Chem. Eur. J. 2013, 19, 14591–14599.
[8] a) W. Q. Wang, L. Wang, Z. S. Li, Z. G. Xie, Chem. Commun. 2016, 52,
5402–5405; b) C. B. He, K. D. Lu, D. M. Liu, W. B. Lin, J. Am. Chem. Soc.
2014, 136, 5181–5184; c) A. Ruyra, A. Yazdi, J. Espin, A. Carne-Sanchez,
N. Roher, J. Lorenzo, I. Imaz, D. Maspoch, Chem. Eur. J. 2015, 21, 2508–
2518; d) Y. Bai, Y. B. Dou, L. H. Xie, W. Rutledge, J. R. Li, H. C. Zhou,
Chem. Soc. Rev. 2016, 45, 2327–2367.
[9] a) L. L. Tan, H. W. Li, Y. C. Qiu, D. X. Chen, X. Wang, R. Y. Pan, Y. Wang,
S. X. A. Zhang, B. Wang, Y. W. Yang, Chem. Sci. 2015, 6, 1640–1644;
b) L. L. Tan, H. W. Li, Y. Zhou, Y. Y. Zhang, X. Feng, B. Wang, Y. W. Yang,
Small 2015, 11, 3807–3813.
[10] K. Jiang, L. Zhang, Q. Hu, D. Zhao, T. Xia, W. Lin, Y. Yang, Y. Cui, Y. Yang,
G. Qian, J. Mater. Chem. B 2016, 4, 6398–6401.
[11] D. A. Gomez-Gualdron, O. V. Gutov, V. Krungleviciute, B. Borah, J. E. Mon-
dloch, J. T. Hupp, T. Yildirim, O. K. Farha, R. Q. Snurr, Chem. Mater. 2014,
26, 5632–5639.
[12] J. H. Cavka, S. Jakobsen, U. Olsbye, N. Guillou, C. Lamberti, S. Bordiga,
K. P. Lillerud, J. Am. Chem. Soc. 2008, 130, 13850–13851.
This work was supported by the National Natural Science
Foundation of China (Nos. 51432001, 51402259, 51472067,
51472217, 51632008, and U1609219) and the Natural Science
Foundation of Zhejiang Province (No. LZ15E020001).
Keywords: drug carriers · drug delivery · medicinal chemistry ·
metal–organic frameworks · pi–pi interactions
[1] L. J. Meng, X. K. Zhang, Q. H. Lu, Z. F. Fei, P. J. Dyson, Biomaterials 2012,
33, 1689–1698.
[2] a) D. Peer, J. M. Karp, S. Hong, O. C. FaroKHzad, R. Margalit, R. Langer,
Nat. Nanotechnol. 2007, 2, 751–760; b) Z. Liu, A. C. Fan, K. Rakhra, S.
Sherlock, A. Goodwin, X. Y. Chen, Q. W. Yang, D. W. Felsher, H. J. Dai,
Angew. Chem. Int. Ed. 2009, 48, 7668–7672; Angew. Chem. 2009, 121,
7804–7808; c) W. Wijagkanalan, S. Kawakami, M. Hashida, Pharm. Res.
2011, 28, 1500–1519; d) B. Y. Lee, Z. L. Li, D. L. Clemens, B. J. Dillon,
A. A. Hwang, J. I. Zink, M. A. Horwitz, Small 2016, 12, 3690–3702.
[3] a) P. P. Bag, D. Wang, Z. Chen, R. Cao, Chem. Commun. 2016, 52, 3669–
3672; b) X. G. Wang, Z. Y. Dong, H. Cheng, S. S. Wan, W. H. Chen, M. Z.
Zou, J. W. Huo, H. X. Deng, X. Z. Zhang, Nanoscale 2015, 7, 16061–
16070.
[4] a) D. A. Gꢃmez-Gualdrꢃn, Y. J. Colꢃn, X. Zhang, T. C. Wang, Y.-S. Chen,
J. T. Hupp, T. Yildirim, O. K. Farha, J. Zhang, R. Q. Snurr, Energy Environ.
Sci. 2016, 9, 3279–3289; b) Y.-S. Wei, M. Zhang, P.-Q. Liao, R.-B. Lin, T.-Y.
Li, G. Shao, J.-P. Zhang, X.-M. Chen, Nat. Commun. 2015, 6, 8348–8354;
c) Q. G. Zhai, X. H. Bu, C. Y. Mao, X. Zhao, P. Y. Feng, J. Am. Chem. Soc.
2016, 138, 2524–2527; d) Z. J. Zhang, Z. Z. Yao, S. C. Xiang, B. L. Chen,
Energy Environ. Sci. 2014, 7, 2868–2899; e) T. M. McDonald, W. R. Lee,
J. A. Mason, B. M. Wiers, C. S. Hong, J. R. Long, J. Am. Chem. Soc. 2012,
134, 7056–7065; f) S. C. Xiang, Y. B. He, Z. J. Zhang, H. Wu, W. Zhou, R.
Krishna, B. L. Chen, Nat. Commun. 2012, 3, 954–962; g) X. L. Cui, K. J.
Chen, H. B. Xing, Q. W. Yang, R. Krishna, Z. B. Bao, H. Wu, W. Zhou, X. L.
Dong, Y. Han, B. Li, Q. L. Ren, M. J. Zaworotko, B. L. Chen, Science 2016,
353, 141–144; h) L. Zhang, K. Jiang, M. Jiang, D. Yue, Y. Wan, H. Xing, Y.
Yang, Y. Cui, B. Chen, G. Qian, Chem. Commun. 2016, 52, 13568–13571;
i) L. Zhang, C. Zou, M. Zhao, K. Jiang, R. Lin, Y. He, C.-D. Wu, Y. Cui, B.
Chen, G. Qian, Cryst. Growth Des. 2016, 16, 7194–7197.
[13] a) C. Y. Sun, C. Qin, X. L. Wang, G. S. Yang, K. Z. Shao, Y. Q. Lan, Z. M. Su,
P. Huang, C. G. Wang, E. B. Wang, Dalton Trans. 2012, 41, 6906–6909;
b) J. Gordon, H. Kazemian, S. Rohani, Mater. Sci. Eng. C 2015, 47, 172–
179.
[14] a) J. Y. An, S. J. Geib, N. L. Rosi, J. Am. Chem. Soc. 2009, 131, 8376–8377;
b) Q. Hu, J. C. Yu, M. Liu, A. P. Liu, Z. S. Dou, Y. Yang, J. Med. Chem. 2014,
57, 5679–5685.
[15] a) H. Maeda, J. Controlled Release 2012, 164, 138–144; b) E. Secret, K.
Smith, V. Dubljevic, E. Moore, P. Macardle, B. Delalat, M. L. Rogers, T. G.
Johns, J. O. Durand, F. Cunin, N. H. Voelcker, Adv. Healthcare Mater.
2013, 2, 718–727.
[16] A. Tsuda, A. Osuka, Science 2001, 293, 79–82.
[17] Y. B. Zhang, S. F. Ali, E. Dervishi, Y. Xu, Z. R. Li, D. Casciano, A. S. Biris,
ACS Nano 2010, 4, 3181–3186.
[5] a) D. T. Genna, L. Y. Pfund, D. C. Samblanet, A. G. Wong-Foy, A. J. Matzg-
er, M. S. Sanford, ACS Catal. 2016, 6, 3569–3574; b) Y. Z. Chen, Q. Xu,
S. H. Yu, H. L. Jiang, Small 2015, 11, 71–76; c) Q. H. Yang, Y. Z. Chen,
Z. Y. U. Wang, Q. Xu, H. L. Jiang, Chem. Commun. 2015, 51, 10419–
10422; d) Q. H. Yang, Q. Xu, S. H. Yu, H. L. Jiang, Angew. Chem. Int. Ed.
2016, 55, 3685–3689; Angew. Chem. 2016, 128, 3749–3753; e) Y. Z.
Chen, C. M. Wang, Z. Y. Wu, Y. J. Xiong, Q. Xu, S. H. Yu, H. L. Jiang, Adv.
Mater. 2015, 27, 5010–5016; f) A. Dhakshinamoorthy, A. M. Asiri, H.
Garcia, Chem. Commun. 2014, 50, 12800–12814.
[6] a) X. M. Lin, G. M. Gao, L. Y. Zheng, Y. W. Chi, G. N. Chen, Anal. Chem.
2014, 86, 1223–1228; b) D. Zhao, X. Y. Wan, H. J. Song, L. Y. Hao, Y. Y.
Su, Y. Lv, Sens. Actuators B 2014, 197, 50–57; c) D. Zhao, J. Zhang, D.
Yue, X. S. Lian, Y. J. Cui, Y. Yang, G. D. Qian, Chem. Commun. 2016, 52,
Manuscript received: April 28, 2017
Accepted manuscript online: June 9, 2017
Version of record online: && &&, 0000
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FULL PAPER
The heat is on: The isoreticular Zr-clus-
ter-based metal–organic framework
(MOF) ZJU-801 was synthesized with
high drug loading capacity for thermal
stimuli-triggered drug release (see
figure, DS=diclofenac sodium), thus it
could be used as a local heating
method for treatment of disease includ-
ing cancer.
&
Drug Delivery
K. Jiang, L. Zhang, Q. Hu, Q. Zhang,
W. Lin, Y. Cui,* Y. Yang, G. Qian*
&& – &&
Thermal Stimuli-Triggered Drug
Release from a Biocompatible Porous
Metal–Organic Framework
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ꢀ 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!