A Bimetallic Metal–Organic Framework Encapsulated with DNAzyme for Intracellular Drug Synthesis and Self-Sufficient Gene Therapy

Article abstract of DOI:10.1002/anie.202016442

Although chemotherapy is one of the most widely used cancer treatments, there are serious side effects, drug resistance, and secondary metastasis. To address these problems, herein we designed a bimetallic metal–organic framework (MOF) encapsulated with DNAzyme for co-triggered in situ cancer drug synthesis and DNAzyme-based gene therapy. Once in cancer cells, MOFs would disassemble and liberate copper ions, zinc ions, and DNAzyme under the acidic environment of lysosomes. Copper ions can catalyze the synthesis of the chemotherapeutic drug through copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction after being reduced to Cu^I; zinc ions act as the cofactor to activate the cleavage activity of DNAzyme. The anticancer drug is synthesized intracellularly and can kill cancer cells on site to minimize side effects to normal organisms. The activated DNAzyme starts gene therapy to inhibit tumor proliferation and metastasis by targeting and cleaving oncogene substrates.

Full text of DOI:10.1002/anie.202016442

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How to cite:
International Edition: doi.org/10.1002/anie.202016442
German Edition: doi.org/10.1002/ange.202016442
Metal–Organic Frameworks
A Bimetallic Metal–Organic Framework Encapsulated with DNAzyme
for Intracellular Drug Synthesis and Self-Sufficient Gene Therapy
Zhao Wang+, Jingsheng Niu+, Chuanqi Zhao,* Xiaohui Wang,* Jinsong Ren, and Xiaogang Qu*
Abstract: Although chemotherapy is one of the most widely
used cancer treatments, there are serious side effects, drug
resistance, and secondary metastasis. To address these prob-
lems, herein we designed a bimetallic metal–organic frame-
work (MOF) encapsulated with DNAzyme for co-triggered in
situ cancer drug synthesis and DNAzyme-based gene therapy.
Once in cancer cells, MOFs would disassemble and liberate
copper ions, zinc ions, and DNAzyme under the acidic
environment of lysosomes. Copper ions can catalyze the
synthesis of the chemotherapeutic drug through copper-
catalyzed azide–alkyne cycloaddition (CuAAC) reaction after
being reduced to CuI; zinc ions act as the cofactor to activate
the cleavage activity of DNAzyme. The anticancer drug is
synthesized intracellularly and can kill cancer cells on site to
minimize side effects to normal organisms. The activated
DNAzyme starts gene therapy to inhibit tumor proliferation
and metastasis by targeting and cleaving oncogene substrates.
somes.[16] By decorating with targeted ligands or exosomes,
these catalysts showed enhanced selectivity to cancer cells
and lessened damage to normal cells. Recently, Rotello and
co-workers reported an AuNPs-based bioorthogonal nano-
zyme that exhibited reversible activity through host-guest
interactions,[17] and Wang et al described an enrichment-
triggered prodrug activation approach allowing for selective
drug release following enrichment.[20] Their work realized the
activation of prodrugs in a more controlled manner. All of
these efforts have made remarkable progress in improving the
therapeutic effect and reducing the side effects by employing
target-controlled bioorthogonal catalysts. As a typical bio-
orthogonal reaction, the CuAAC reaction has been widely
used in biomacromolecules labeling,[21] organic synthesis,[22]
and drug discovery,[23] etc. Cu+ plays a key role in the CuAAC
reaction, but Cu+ is toxic to living cells and could induce the
generation of reactive oxygen species (ROS).[24] An ideal
bioorthogonal catalyst is required to possess good catalytic
activity while doing no harm to normal cells. We previously
developed a biocompatible heterogeneous MOF-Cu catalyst
for localized drug synthesis in subcellular organelles,[18] in
which the cytotoxicity of free Cu+ was avoided by using the
heterogeneous metal catalyst. Zeolitic imidazolate frame-
work-8 (ZIF-8) was considered to be the suitable delivery
vehicle for its pH-responsive degradation ability.[25–27] In-
spired by this, here we designed a Cu/Zn bimetallic MOF,
which would release copper ions in the acidic microenviron-
ment of lysosomes after uptaken by cancer cells. The
controlled release behavior not only provides the foundation
for catalyzing the CuAAC reaction but also guarantees
biological safety.
Another key challenge in cancer therapy is recurrence and
metastasis.[28] The cancer cells that survived the treatment
may metastasize through the body, so the therapeutic effect of
chemotherapy alone is limited. To overcome drug resistance
and secondary metastasis, many works focus on blocking
metastasis-associated pathways with gene therapy.[29–33] DNA-
zyme,[34–36] for its flexible programmability, relative stability in
serum, powerful enzymatic turnover capability, and low cost,
is regarded as one of the most available gene therapy
tools.[37–39] Featured with cofactor-dependent catalytic activity,
DNAzymes have been widely used to build sensing platforms
for metal ions,[40–42] small molecules,[43,44] bio-macromole-
cules,[45] and bacteria.[46] Recently, DNAzymes have been
actively investigated for therapeutic purposes.[47] For instance,
the RNA-cleaving DNAzyme has been used as a potent gene
silencing tool to target and cleave the substrates of inter-
est,[48,49] and thus exhibits great potential for cancer treat-
ment.[50–56] Tan and co-workers used MnO2 nanosheets to
deliver DNAzyme into cancer cells, the cleavage activity of
Introduction
Chemotherapy is one of the most traditional treatments
for cancer. Classic anticancer drugs inevitably do damage to
normal cells or tissues while killing cancer cells.[1–3] To
minimize side effects, drugs are expected to be activated or
synthesized directly in target cells.[4–6] The booming bioor-
thogonal chemistry paves the way for synthesizing therapeutic
molecules in vivo. Many bioactive molecules have been
available by various bioorthogonal reactions,[7–12] and a series
of bioorthogonal catalysts have been successfully developed
for the activation of prodrugs at the desired location.[13–20]
Bradley and co-workers reported the synthesis of two
cytotoxic agents simultaneously in glioblastoma cells by
palladium catalysts.[14] Unciti-Broceta et al. achieved the
cell-specific release of the anticancer drug panobinostat by
palladium nanosheets wrapped with cancer-derived exo-
[*] Z. Wang,[+] J. Niu,[+] Dr. C. Zhao, Prof. X. Wang, Prof. J. Ren, Prof. X. Qu
Laboratory of Chemical Biology and
State Key Laboratory of Rare Earth Resource Utilization
Changchun Institute of Applied Chemistry
Chinese Academy of Sciences, Changchun, Jilin 130022 (P. R. China)
and
University of Science and Technology of China
Hefei, Anhui 230026 (P. R. China)
E-mail: chuanqizhao12@yahoo.com
hxwangjilin@126.com
xqu@ciac.ac.cn
[+] These authors contributed equally to this work.
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202016442.
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DNAzyme can be highly activated by Mn2+ that generated
ably avoids the side effects of traditional chemotherapy but
also blocks tumor metastasis effectively.
through the reduction reaction of MnO2 in the presence of
intracellular glutathione (GSH).[50] Wang et al designed
a DNAzyme-loaded metal–organic framework for self-suffi-
cient gene therapy.[56] These works demonstrated that DNA- Results and Discussion
zymes have great potential for the treatment of cancer.
Previous studies have shown that the proliferation and
migration of cancer cells have a close relationship with some
oncogenes,[29–33] which means DNAzymes can be designed
reasonably to cleave metastasis-associated oncogenes, ach-
ieving efficient inhibition of metastasis. However, to our
knowledge, there is no report to combine bioorthogonal
intracellular drug synthesis and DNAzyme-based gene ther-
apy together for synergistic cancer treatment.
Herein, a combined chemotherapy-gene therapy nano-
platform was established by encapsulating human early
growth response-1 (EGR-1) targeted DNAzyme into Cu/Zn
bimetallic MOF nanoparticles. In this design, DNAzyme acts
as a tool for gene silencing. The bimetallic MOF nanoparticles
not only act as the shelter for DNAzyme from digestion
during delivery, but also as the supplier of cofactor (Zn2+) for
DNAzyme and as the catalyst for the CuAAC reaction. As
illustrated in Figure 1. after endocytosis by cancer cells, the
nanoparticles will disassemble under the acidic environment
of lysosomes, accompanied with releasing of Zn2+, Cu2+, and
DNAzyme. Cu2+ is reduced to Cu+ by sodium ascorbate to
trigger the CuAAC reaction, and zinc ions work as the
cofactor to initiate the cleavage reaction. The resveratrol
derivative generated from the above CuAAC reaction can kill
the cancer cells with minimal side effects, and the DNAzyme
activated by Zn2+ strongly inhibits the proliferation and
metastasis of cancer cells. This combined therapy not only
The Cu/ZIF-8 nanoparticles were prepared through
a simple one-step method by mixing Cu(NO3)2, Zn(NO3)2
solution, and 2-methylimidazole in methanol under stirring.
Molar percentages of 0%, 10%, 25%, and 40% Cu(NO3)2 to
Zn(NO3)2 were used in these experiments. The nanoparticles
were named as ZIF-8, 10%Cu/ZIF-8, 25%Cu/ZIF-8, and
40%Cu/ZIF-8, respectively. The as-prepared nanoparticles
had a dodecahedron structure and the average diameter was
determined to be about 120 nm (Supporting Information,
Figure S1a–d). Inductively coupled plasma-optical emission
spectrometry (ICP-OES) results showed that the exact
copper content of Cu/ZIF-8 nanoparticles was lower than
the Cu/Zn ratios used in this experiment (Supporting
Information, Figure S4; the copper content of Cu/ZIF-8
nanoparticles are 0%, 7.0%, 12.9%, and 18.2%, respective-
ly), and the element mapping images also showed that the
copper was uniformly distributed throughout the nanoparti-
cles (Figure S2), which indicated that the bimetallic MOF was
prepared successfully. X-ray diffraction showed that the
nanoparticles remained to be good crystals after copper
incorporation (Supporting Information, Figure S5). Although
a higher copper content would offer a better catalytic effect,
the abundant copper might be toxic to normal cells. There-
fore, we evaluated the cytotoxicity of Cu/ZIF-8 nanoparticles
to MCF-7 cells (Supporting Information, Figure S9) and
chose 25%Cu/ZIF-8 for further application.
The DNAzyme@Cu/ZIF-8 nanoparticles were prepared
in a similar way. To achieve the more robust encapsulation of
DNAzyme, DNAzyme was simultaneously mixed with metal
ions and organic ligand to obtain the DNAzyme@Cu/ZIF-8
nanoparticles, so the DNAzyme could be encapsulated
throughout the nanoparticles instead of unstable adsorption
on the surface. After the encapsulation of DNAzymes, the
average diameter of nanoparticles got slightly larger (Fig-
ure 2a; Supporting Information, Figure S3), and the zeta
potential of nanoparticles changed from + 21.8 mV to
À24.6 mV (Figure 2d). The formation of crystals did not get
disturbed by DNAzyme (Figure 2b). The distribution of
phosphorus indicated the successful encapsulation of DNA-
zyme into Cu/ZIF-8 nanoparticles (Figure 2c), which were
further confirmed by the thermal gravimetric analysis (Sup-
porting Information, Figure S6) and UV/Vis spectra (Fig-
ure 2e).
Subsequently, we investigated the DNAzyme release
behavior and substrate cleavage ability of the DNAzyme@-
Cu/ZIF-8 under different pH stimuli. Firstly, the stability of
DNAzyme@Cu/ZIF-8 in biological fluids was evaluated. A
very small amount of copper ions and zinc ions leach out from
the nanoparticles even after being immersed in simulated
body fluid (SBF) for 24 h (Supporting Information, Fig-
ure S7), which ensured that the metal ions would not undergo
premature liberation to cause certain side effects during the
delivery process. Then the DNAzyme loading capacity (DLC)
Figure 1. a) The pH-responsive degradation behavior of DNAzyme@-
Cu/ZIF-8, the corresponding CuAAC reaction for in situ chemotherapy,
and mRNA cleavage reaction for gene therapy. b) A smart DNAzy-
me@Cu/ZIF-8 nanoplatform for the synergistic chemo-gene therapy.
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Figure 2. a) SEM and TEM (inset) images of DNAzyme@Cu/ZIF-8
nanoparticles. b) XRD patterns of ZIF-8, Cu/ZIF-8, and DNAzyme@-
Cu/ZIF-8 nanoparticles. c) TEM images and element mapping of
DNAzyme@Cu/ZIF-8 (Scale bar: 100 nm). d) Zeta potential of Cu/ZIF-
8 and DNAzyme@Cu/ZIF-8. e) UV/Vis absorbance spectra of Cu/ZIF-8
(black) and DNAzyme@Cu/ZIF-8 (red), and characteristic absorption
peak of DNAzyme@Cu/ZIF-8 (insert).
was calculated to be 9.7 wt% (Supporting Information,
Figure S8). Only 12% DNAzyme was liberated at pH 7.4,
while up to 80% DNAzyme was released at pH 5.5 after
incubation for 24 h (Figure 3a), which was mainly ascribed to
the breakdown of the coordinate bonds between zinc and
imidazole by the acidic medium. After that, we investigated
the effect of Zn2+ on the catalytic activity of DNAzyme for
the cleavage reaction. When the concentration of Zn2+
reached 200 mM, the substrate could be cleaved completely
(Figure 3b). As expected, for DNAzyme@Cu/ZIF-8, the high
catalytic activity on the cleavage reaction could only be
observed under the acidic stimulus (Figure 3c).
Figure 3. a) The pH-responsive DNAzyme release from DNAzyme@-
Cu/ZIF-8 upon their exposure to different pH stimuli. b) PAGE analysis
of DNAzyme mediated cleavage reaction under different concentra-
tions of Zn2+. c) pH-stimulated DNAzyme@Cu/ZIF-8 mediated DNA-
zyme and cofactor release for boosting the cleavage reaction. d) The
schematic diagram of DNAzyme@Cu/ZIF-8 catalyzed Huisen 1,3-
dipolar cycloaddition reaction between azides, 1, and terminal alkynes,
2, to give the fluorescent molecule, 3. e) The fluorescent spectra of the
click reaction solution with (black) and without (red) DNAzyme@Cu/
ZIF-8 catalyst. f) The changes of fluorescence spectra under different
times of the reaction with DNAzyme@Cu/ZIF-8 catalyst (from 0 to
150 min).
We then tested the catalytic activity DNAzyme@Cu/ZIF-
8 on the CuAAC reaction in vitro. Both the precursor
molecules 1 and 2 were nonfluorescent, but the CuAAC
reaction between 1 and 2 would give a product 3 which
emitted strong blue fluorescence (Figure 3d). After the
addition of DNAzyme@Cu/ZIF-8 nanoparticles, an obvious
increase of fluorescence intensity was observed (Figure 3e),
about 10 fold fluorescence enhancement for 2.5 h at 378C
(Figure 3 f). These results confirmed that the DNAzyme@Cu/
ZIF-8 could catalyze the CuAAC reaction in test tubes.
Cytotoxicity assays indicated that DNAzyme@Cu/ZIF-8
have good biocompatibility even at the concentration of
40 mgmLÀ1 (Supporting Information, Figure S9), thus the
concentration of nanoparticles used in the cell experiments
was set at 40 mgmLÀ1. Firstly, we evaluated the cellular uptake
behavior of DNAzyme@Cu/ZIF-8 by confocal laser scanning
microscope (CLSM). In these assays, fluorescent FAM-
DNAzyme@Cu/ZIF-8 was employed. Compared to the free
FAM-DNAzyme treated cells, the cells treated with FAM-
DNAzyme@Cu/ZIF-8 exhibited stronger intracellular fluo-
rescence (Figure 4a), confirming that the nanoparticles could
efficiently deliver DNAzyme into the cells (Supporting
Information, Figure S10). Then the internalization of nano-
particles was quantified by flow cytometry and ICP-MS. The
fluorescence intensity gradually increased and reached a pla-
teau after 10 h observed by flow cytometry (Supporting
Information, Figure S11). The ICP-MS measurements
showed that the total concentration of Zn2+ and Cu2+ in cells
was significantly increased after DNAzyme@Cu/ZIF-8 treat-
ment (Figure 4b), indicating that the DNAzyme@Cu/ZIF-8
nanoparticles could be uptaken effectively. As indicated in
Figure 3b, 200 mM Zn2+ was needed to cleave the substrate
completely, so the improved intracellular Zn2+ was adequate
to activate DNAzymes. Also, the released Cu2+ was sufficient
to boost the CuAAC reaction intracellularly.
Then we explored the performance of DNAzyme@Cu/
ZIF-8 as the catalyst for the CuAAC reaction in MCF-7 cells.
As displayed in CLSM images, the DNAzyme@Cu/ZIF-8
treated cells showed much more intensive blue fluorescence
than the controls (Figure 4d). The flow cytometry analysis
also indicated the significant increase of fluorescence in cells
treated with DNAzyme@Cu/ZIF-8 (Figure 4c; Supporting
Information, Figure S13). These results confirmed that DNA-
zyme@Cu/ZIF-8 could catalyze the CuAAC reaction in living
cells. Next, we explored whether the precursor molecule 4
could react with molecule 5 to give the active drug molecule 6
by the catalysis of DNAzyme@Cu/ZIF-8 (Figure 1a). The
product 6 is a resveratrol derivative, which can act as the
antitumor drug.[57–60] Cytotoxicity assays indicated that both
precursors 4 and 5 had negligible cytotoxicity to MCF-7 cells
even at the concentration of 50 mM (Supporting Information,
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been directly observed by LC-MS analysis (Supporting
Information, Figure S16).
Given that EGR-1 is closely related to the proliferation
and migration of cancer cells,[29,33] DNAzyme used in this
experiment is designed to target and cleave the EGR-
1 mRNA. The 8–17 and 10–23 DNAzymes are the two most
comprehensively studied RNA-cleaving DNAzymes, and
both are initially discovered by Gerald Joyce in 1997.[61] The
EGR-1 targeted DNAzyme used here was one kind of 10–23
DNAzymes, which has been proved effective in previous
reports.[50,56] To avoid the interference of potential gene
silencing mechanism, we also introduced a control DNA
(cDNA) that had a different nucleotide on the catalytic core
with the original DNAzyme, which made it unable to cleave
EGR-1 mRNA even with the concentration of cofactor
(Zn2+) up to 1 mM (Supporting Information, Figure S17). The
qRT-PCR (Figure 4e) and western blot analysis (Figure 4 f)
results showed that the expression of the EGR-1 mRNA had
been strongly inhibited in DNAzyme@Cu/ZIF-8 treated cells,
while the expression of the EGR-1 mRNA was almost not
affected in the controls, implying that the cleavage mediated
by DNAzyme played the dominant role in gene silencing.
Then we evaluated the influence of DNAzyme@Cu/ZIF-8 on
cell proliferation and metastasis. As shown in the Supporting
Information, Figure S18, cell proliferation was decreased
obviously after treatment with DNAzyme@Cu/ZIF-8. More-
over, the transwell invasion assay showed that the invasive
ability of MCF-7 cells was significantly weakened after
DNAzyme@Cu/ZIF-8 treatment (Figure 4g,h). These results
indicated that DNAzyme@Cu/ZIF-8 had the potential to
inhibit cell proliferation and metastasis.
After confirming the performance of the DNAzyme@Cu/
ZIF-8 nanoplatform as the catalyst for the CuAAC reaction
and the gene silencing tool for the cleavage reaction, we
hypothesized that the synergistic effect could enhance the
treatment outcomes. Firstly, we compared the cytotoxicity of
DNAzyme@Cu/ZIF-8 to different cell lines, the cell viability
analysis (Supporting Information, Figure S19) showed that
the DNAzyme@Cu/ZIF-8 nanoparticles exhibited stronger
cytotoxicity towards MCF-7 cells than normal cells (293T cells
and LO2 cells), which could be attributed to the higher EGR-
1 mRNA expression level in cancer cells.[62,63] Then the
synergistic effect of the designed nanoplatform was evaluat-
ed. As for the two controls, we prepared cDNA@Cu/ZIF-8 by
encapsulating the cDNA into Cu/Zn bimetallic MOF, and
DNAzyme@ZIF-8 by encapsulating the DNAzyme into the
pure ZIF-8 MOF, respectively. As shown in the Supporting
Information, Figure S20, the cDNA@Cu/ZIF-8 and DNAzy-
me@ZIF-8 inhibited the proliferation of MCF-7 cells by 63%
and 40%, respectively, while the DNAzyme@Cu/ZIF-8
inhibited the cell proliferation up to 75%. Moreover, the
apoptotic ratio of the cells treated with DNAzyme@Cu/ZIF-8
increased to 53.9%, which was much higher than that of gene
therapy alone (24.7%) or just in situ drug synthesis (35.0%;
Supporting Information, Figures S21, S22). The live/dead cell
assay also demonstrated our combined DNAzyme@Cu/ZIF-8
system possesses better therapeutic performance (Supporting
Information, Figure S23). Therefore, the DNAzyme@Cu/
Figure 4. a) CLSM images of MCF-7 cells after different treatments for
10 h: PBS (I), free FAM-DNAzyme (II), and FAM-DNAzyme@Cu/ZIF-8
(III). Scale bar: 20 mm. b) ICP-MS analysis of Cu and Zn content in
MCF-7 cells prior to and after 40 mgmLÀ1 DNAzyme@Cu/ZIF-8 treat-
ment. c) The flow cytometry analysis of fluorescence changes, control
(I), precursor 1 + precursor 2 + sodium ascorbate (II), DNAzyme@-
Cu/ZIF-8 (III), precursor 1 + precursor 2 + sodium ascorbate +
DNAzyme@Cu/ZIF-8 (IV), respectively. d) Fluorescence images of
MCF-7 cells treated without (I–III) and with (IV–VI) DNAzyme@Cu/
ZIF-8 catalyst. bright field image of cells (I), emission of the product 3
(II), merging with I and II (III), bright field image of cells (IV),
emission of the product 3 (V), merging with IV and VVI. Scale
bar=20 mm. e) qRT-PCR analysis of EGR-1 mRNA and f) western blot
analysis of EGR-1 protein in MCF-7 cells with different treatments:
PBS (I), cDNA@Cu/ZIF-8 (II), free DNAzyme (III), and DNAzyme@-
Cu/ZIF-8 (IV). g) Microscope images of MCF-7 cells crossing the
transwell membrane after incubation for 24 h and h) quantification by
a microplate reader with different treatments as described before.
Scale bar=50 mm. Results were presented as mean Æ standard
deviation (SD) (n=3)(**p<0.01, ***p<0.001).
Figure S14). Compared to the cells just treated with precur-
sors (4 and 5) or DNAzyme@Cu/ZIF-8, the cells treated with
both precursors and DNAzyme@Cu/ZIF-8 showed a dramatic
decrease in cell viability (Supporting Information, Fig-
ure S15), demonstrating the synthesized drug molecule 6 with
strong cytotoxic effect. Furthermore, the final product 6 has
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ZIF-8 nanoplatform was successfully developed for better
cancer treatment.
particles could effectively accumulate at tumor sites owing to
the enhanced permeability and retention (EPR) effect. After
that, the therapeutic performance of DNAzyme@Cu/ZIF-8
was evaluated on the orthotopic-transplant metastatic model
of nude mice. Compared with the control groups, the
strongest inhibition effect on tumor growth was observed in
DNAzyme@Cu/ZIF-8 dosed group (Figure 5a–c; Supporting
Information, Figure S27). In addition, the DNAzyme@Cu/
ZIF-8 nanoparticles showed no obvious influence on the body
weight of mice (Figure 5d). Metastasis is one of the main
reasons for the failure of cancer treatment, therefore re-
straining metastasis is the key in the treatment of cancer.
There was severe metastasis on the lungs of mice dosed with
saline and cDNAzyme@Cu/ZIF-8, and lessened metastasis on
the lungs of mice dosed with DNAzyme@ZIF-8. However, no
obvious metastatic nodules on the lungs was observed in
DNAzyme@Cu/ZIF-8 treated group (Figure 5e), H&E stain-
ing of lungs (Figure 5 f) further demonstrated DNAzyme@-
Cu/ZIF-8 was effective for containment of metastasis. Taken
together, our designed DNAzyme@Cu/ZIF-8 nanoparticles
could inhibit both tumor growth and metastasis.
Encouraged by the excellent anti-proliferation and anti-
metastasis performance in vitro, we further evaluate the
therapeutic effects of DNAzyme@Cu/ZIF-8 in vivo. Firstly,
the toxicology of nanoparticles was investigated, the hemol-
ysis analysis and H&E staining of main organs results
(Supporting Information, Figures S24, S25) both illustrated
the good biocompatibility of nanoparticles. Subsequently, the
biodistribution of DNAzyme@Cu/ZIF-8 nanoparticles was
explored. Both the in vivo and in vitro fluorescence images
(Supporting Information, Figure S26a,b) confirmed that the
nanoparticles were mainly located at tumor sites, and the ICP-
MS results (Supporting Information, Figure S26c) also
showed that the released zinc ions mainly existed in the
tumor, which indicated that the DNAzyme@Cu/ZIF-8 nano-
Conclusion
We have designed and synthesized a combined therapy
nanoplatform by encapsulating the therapeutic DNAzyme
into Cu/Zn bimetallic MOF for intracellular drug synthesis
and self-sufficient gene therapy. The designed nanoplatform
exhibits sensitive pH-responsive release behavior. After
exposure to acid stimulation, the bimetallic MOFs collapse
to liberate the copper and zinc ions and DNAzyme, copper
ions act as the catalyst for the CuAAC reaction, and zinc ions
act as the cofactor for the cleavage reaction. To our knowl-
edge, there is the first report to combine bioorthogonal
intracellular drug synthesis and DNAzyme-based gene ther-
apy together for synergistic cancer treatment. This combined
therapy can not only ably avoids the side effects of traditional
chemotherapy by intracellularly synthesizing drug molecule,
but also effectively inhibit tumor metastasis by cleaving the
oncogene substrate, thus holding great potential for the
synergistic treatment of metastatic cancer.
Acknowledgements
This work was supported by the National Key R&D Program
of China (2019YFA0709202), NSFC (21820102009, 21871249,
and 91856205), and Key Research Program of Frontier
Sciences of CAS (QYZDY-SSW-SLH052).
Figure 5. a) Images of the dissected tumors after different treatments
for 21 days: PBS (I), DNAzyme@ZIF-8 (II), cDNA@Cu/ZIF-8 (III), and
DNAzyme@Cu/ZIF-8 (IV). Scale bar=2 cm. b) Changes in tumor
volumes after different treatments as described before. c) Weight of
the dissected tumors after different treatments (21 days) as described
before. d) The body weight changes of MCF-7 tumor-bearing mice after
different treatments as described before. e) Images of the dissected
lungs after different treatments (21 days) as described before. f) lung
tissue staining by H&E after different treatments (21 days) as
described before. Scale bars=400 mm. Results were presented as
mean Æ standard deviation (SD) (n=4) (*p<0.05, **p<0.01,
***p<0.001).
Conflict of interest
The authors declare no conflict of interest.
Keywords: bimetallic MOFs · click reaction · DNAzyme ·
intracellular drug synthesis · metastasis
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ꢀ 2021 Wiley-VCH GmbH
www.angewandte.org
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Angewandte
Research Articles
Chemie
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Manuscript received: December 10, 2020
Revised manuscript received: February 25, 2021
Accepted manuscript online: March 19, 2021
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Version of record online: && &&
,
&&&&
&&&&
www.angewandte.org
ꢀ 2021 Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 9
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Research Articles
Metal–Organic Frameworks
A synergetic therapy nanoplatform was
developed by encapsulating the ther-
apeutic DNAzyme into Cu/Zn bimetallic
MOF for intracellular drug synthesis and
self-sufficient gene therapy. This design
can not only ably avoids the side effects of
traditional chemotherapy, but also effec-
tively inhibit tumor metastasis by cleav-
ing the oncogene substrate.
Z. Wang, J. Niu, C. Zhao,* X. Wang,*
J. Ren, X. Qu*
&&&& — &&&&
A Bimetallic Metal–Organic Framework
Encapsulated with DNAzyme for
Intracellular Drug Synthesis and Self-
Sufficient Gene Therapy
Angew. Chem. Int. Ed. 2021, 60, 2 – 9
ꢀ 2021 Wiley-VCH GmbH
www.angewandte.org
&&&&
These are not the final page numbers!