Nanocomposite incorporating V2O5 nanowires and gold nanoparticles for mimicking an enzyme cascade reaction and its application in the detection of biomolecules

Article abstract of DOI:10.1002/chem.201400309

Artificial enzyme mimics are a current research interest, and many nanomaterials have been found to display enzyme-mimicking activity. However, to the best of our knowledge, there have not hitherto been any reports on the use of pure nanomaterials to construct a system capable of mimicking an enzyme cascade reaction. Herein, we describe the construction of a novel nanocomposite consisting of V₂O₅ nanowires and gold nanoparticles (AuNPs) through a simple and facile chemical method, in which V ₂O₅ and AuNPs possess intrinsic peroxidase and glucose oxidase (GOx)-like activity, respectively. Results suggest that this material can mimic the enzyme cascade reaction of horseradish peroxidase (HRP) and GOx. Based on this mechanism, a direct and selective colorimetric method for the detection of glucose has been successfully designed. Because single-strand and double-strand DNA (ssDNA and dsDNA) have different deactivating effects on the GOx-like activity of AuNPs, the sensing of target complementary DNA can also be realized and disease-associated single-nucleotide polymorphism of DNA can be easily distinguished. Our study opens a new avenue for the use of nanomaterials in enzyme mimetics, and holds promise for the further exploration of nanomaterials in creating alternative catalytic systems to natural enzymes.

Full text of DOI:10.1002/chem.201400309

DOI: 10.1002/chem.201400309
Full Paper
&
Artificial Enzymes
Nanocomposite Incorporating V2O5 Nanowires and Gold
Nanoparticles for Mimicking an Enzyme Cascade Reaction and Its
Application in the Detection of Biomolecules
Konggang Qu,[a, b] Peng Shi,[a, b] Jinsong Ren,[a] and Xiaogang Qu*[a]
Abstract: Artificial enzyme mimics are a current research in-
terest, and many nanomaterials have been found to display
enzyme-mimicking activity. However, to the best of our
knowledge, there have not hitherto been any reports on the
use of pure nanomaterials to construct a system capable of
mimicking an enzyme cascade reaction. Herein, we describe
the construction of a novel nanocomposite consisting of
V2O5 nanowires and gold nanoparticles (AuNPs) through
a simple and facile chemical method, in which V2O5 and
AuNPs possess intrinsic peroxidase and glucose oxidase
(GOx)-like activity, respectively. Results suggest that this ma-
terial can mimic the enzyme cascade reaction of horseradish
peroxidase (HRP) and GOx. Based on this mechanism,
a direct and selective colorimetric method for the detection
of glucose has been successfully designed. Because single-
strand and double-strand DNA (ssDNA and dsDNA) have dif-
ferent deactivating effects on the GOx-like activity of AuNPs,
the sensing of target complementary DNA can also be realiz-
ed and disease-associated single-nucleotide polymorphism
of DNA can be easily distinguished. Our study opens a new
avenue for the use of nanomaterials in enzyme mimetics,
and holds promise for the further exploration of nanomateri-
als in creating alternative catalytic systems to natural en-
zymes.
vironmental detection,[4–9] engineering these synthetic nano-
components into organized functional systems mimicking
complex natural enzyme systems, especially for enzyme-cata-
lyzed cascade reactions, still remains a major challenge in this
field.[10]
Introduction
Developing artificial enzymes has received great interest re-
cently owing to the advantages that they offer over natural en-
zymes in practical applications, such as the low cost of their
preparation and purification, superior operational stability, and
high stability to environmental conditions.[1] The emergence
and recent advances of nanoscience and nanotechnology have
opened new opportunities for the design and construction of
enzyme mimics.[2] The exciting first report of intrinsic horserad-
ish peroxidase (HRP)-like activity of inert ferromagnetic nano-
particles aroused great attention for further innovative re-
search on nanomaterials in the enzyme mimetic field.[3] There-
after, more nanomaterial-based peroxidase mimics emerged in
succession, showing that graphene oxide,[4] carbon nano-
tubes,[5] carbon dots,[6] nanoceria,[7] gold nanoparticles
(AuNPs),[8] and V2O5 nanowires[9] may also be potential substi-
tutes for natural enzymes. Although these enzyme mimics
showed promising potential in biomedical applications and en-
Recently, AuNPs have been found to be capable of catalyti-
cally oxidizing glucose to produce gluconates in a “green”
manner. This transformation resembles that performed by the
natural enzyme glucose oxidase (GOx), which catalyzes the oxi-
dation of glucose with the co-substrate oxygen (O2) to pro-
duce gluconate and H2O2.[8b] V2O5 nanowires exhibit an intrinsic
HRP-like activity towards classical peroxidase substrates such
as 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)
in the presence of H2O2.[9a] These V2O5 nanowires show an opti-
mum reactivity at pH 4.0 and their catalytic activity is depen-
dent on their concentration. Herein, we report the construction
of a novel nanocomposite with dual enzyme-mimetic activities
by combining V2O5 nanowires and AuNPs. On the basis of the
unique and attractive properties of these components, this
system could be applied as a robust nanoreactor for mimicking
an enzyme cascade reaction without the need for the natural
enzymes. Furthermore, the system can not only be used for
the detection of glucose, but can also serve as a nanoprobe
for colorimetric sensing of target DNA with high sensitivity and
selectivity.
[a] K. Qu, P. Shi, Prof. J. Ren, Prof. X. Qu
Laboratory of Chemical Biology, Division of Biological Inorganic Chemistry
State Key Laboratory of Rare Earth Resource Utilization
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences
Changchun, Jilin 130022 (China)
Fax: (+86)431-85262656
E-mail: xqu@ciac.ac.cn
[b] K. Qu, P. Shi
University of Chinese Academy of Sciences
Beijing, 100039 (China)
Results and Discussion
The preparation of the nanocomposite and the enzyme-mim-
etic catalytic cascade reaction are illustrated in Scheme 1. V2O5
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201400309.
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Scheme 1. Schematic representation of the preparation of V2O5-PDA-AuNP
composite material and its mimicking of an enzyme cascade reaction pro-
cess.
nanowires were prepared by a hydrothermal method as de-
scribed elsewhere.[9a] A V2O5-polydopamine (PDA) composite
could be readily synthesized because dopamine (DA) can self-
polymerize at alkaline pH values and spontaneously deposit
uniform polydopamine films on the surfaces of V2O5 nano-
wires.[11] The thickness of such a uniform coating can be pre-
cisely controlled by adjusting the DA concentration. The for-
mation of the PDA layer is of critical importance for the syn-
thesis of the composite material. On the one hand, PDA con-
tains plenty of functional groups that provide abundant heter-
ogeneous nucleation and anchor sites for AuNPs and can
facilitate the formation of uniform and ultrafine AuNPs. On the
other hand, the PDA layer serves to protect the structure of
the V2O5 nanowires from damage by the strong reducing
agent NaBH4 used in the synthesis of AuNPs. Thus, AuNPs
were synthesized by NaBH4 reduction using PDA as a template.
The steps of the procedure are described in the Experimental
Section. The morphologies and compositions of these materi-
als were fully characterized and analyzed by TEM, SEM, UV/Vis,
FTIR, thermogravimetric analysis (TGA), and X-ray photoelec-
tron spectroscopy (XPS) measurements.[12]
Figure 1. TEM images of (A) V2O5 nanowires, (B) V2O5-PDA, (C) V2O5-PDA-
AuNP composite, and (D) AuNPs on the surface of V2O5-PDA.
When the V2O5 nanowires were dispersed in water, a clear,
light-yellow, homogeneous suspension was obtained that
showed no obvious absorbance peak in the UV/Vis range (Fig-
ure 2A). After coating with PDA, the suspension obtained was
brown in color, indicating stronger absorption over the UV/Vis
range than that of the V2O5 nanowires. The peak at 280 nm
may be ascribed to the absorption of PDA. The UV/Vis spec-
trum of V2O5-PDA-AuNP features an obvious peak at 520 nm,
which indicates the presence of AuNPs, and is similar to the
peak seen for AuNPs of size about 5 nm alone.[13] FTIR spectra
(Figure 2B) were used to identify the functional groups present
on V2O5-PDA, and the observed peaks at 1502 and 1616 cmÀ1
are consistent with the indole or indoline structures proposed
previously.[14] The broad and intense peak centered at
3159 cmÀ1 and the band at 1286 cmÀ1, which relate to CÀOH
stretching and ÀOH bending vibrations, imply the presence of
a large number of residual hydroxyl groups.[14] The TGA curve
indicated about 30 wt% PDA on the surface of the V2O5 nano-
wires, which was lost at about 3308C (Figure 2C).
XPS analysis confirmed that the V2O5 nanowires contained
31.2% V and 68.8% O (Figure 3A). Figure 3C shows the core-
level binding energies for the V2p peaks. The binding energies
for vanadium 2p3/2 and 2p1/2 observed at 517.2 and 524.5 eV,
respectively, are in good agreement with those of V5+ in V2O5
(Figure 3C).[15] The corresponding O1s spectrum is shown in
Figure 3D; the O1s spectrum is broad and asymmetric and
can be deconvoluted into two peaks, indicating the presence
of two different oxygen species. The peaks at binding energies
of 530 and 531.5 eV can be attributed to O1s of V2O5 and OH,
respectively.[15] The formation of V2O5-PDA was further con-
firmed by XPS. As shown in Figure 3B, peaks corresponding to
carbon, oxygen, and nitrogen were seen. Only a small amount
of vanadium was also observed, indicating the formation of
a near-complete PDA coating on the V2O5 nanowires.
The morphologies of the three kinds of V2O5 materials were
firstly characterized by TEM and SEM measurements. Figure 1
and Figure S1 in the Supporting Information show typical TEM
and SEM images, respectively. The freshly synthesized V2O5
nanowires were of various sizes of up to several mm in length
and several tens of nm in width.[9a] A typical image of V2O5-
PDA shows that it has a distinctly rougher surface than that of
the V2O5 nanowires, confirming that PDA was coated on the
surface of the V2O5. An SEM image (Figure S1B) revealed that
the V2O5-PDA nanowires were much shorter than those of
pure V2O5, typically several hundreds of nm in length, because
ultrasonication broke up the long V2O5 nanowires. The smaller
size favored dispersion of the V2O5 in aqueous solution. As
shown in Figure 1C, D, typical TEM images of the V2O5-PDA-
AuNP composite revealed that isolated, homogeneous, and ul-
trafine spherical AuNPs with a mean size of about 4.5 nm were
extensively decorated on the V2O5-PDA surface. SEM images
(Figures S1C and S1D) showed the V2O5-PDA-AuNP composite
to be well-dispersed with no aggregation, and that AuNPs
were densely assembled on the surfaces of all of the nano-
wires.
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Figure 3. XPS spectra of (A) V2O5 showing V and O peaks and (B) V2O5-PDA
showing C, N, O, and V peaks; (C) V2p and (D) O1s spectra of the V2O5 nano-
wires.
Figure 4. (A) The intrinsic peroxidase-like activity of V2O5 in 10 mm NaOAc
buffer of different pH values. (B) The intrinsic peroxidase-like activities of
V2O5, V2O5-PDA, and V2O5-PDA-AuNP in pH 4.0, 10 mm NaOAc buffer.
Figure 2. (A) UV/Vis spectra of V2O5, V2O5-PDA, V2O5-PDA-AuNP, and 5 nm
AuNPs alone; (B) FTIR spectra of V2O5 and V2O5-PDA; (C) TGA curves of V2O5
and V2O5-PDA.
ABTS and glucose in pH 7.0 NaOAc buffer (10 mm). In this pro-
cess, the AuNPs mimicked GOx in catalyzing the oxidation of
glucose to gluconic acid. In the meantime, the substrate
oxygen was converted into H2O2. 2) The mixture was then ad-
justed to pH 4.0 by adding pH 4.0 NaOAc buffer (100 mm),
whereupon H2O2 was reduced by the V2O5 nanowires, mimick-
ing peroxidase in the presence of ABTS as co-substrate at
pH 4.0 and producing a green color.[4] The detailed procedure
is described in the Experimental Section. According to this
principle, we designed a colorimetric method for the detection
of glucose using V2O5-PDA-AuNP for the enzyme-mimicking
cascade reaction. Figure 5A shows the time-dependent ab-
sorbance changes at 415 nm versus the concentration of glu-
cose. The absorbance at 400 nm gradually increased with in-
creasing concentration of glucose, indicating that the addition
of glucose was effective in accelerating the enzyme cascade re-
action. As shown in Figure 5B, a good linear correlation (R2 =
0.99) was observed over the concentration range 0–10 mm and
a detection limit of 0.5 mm was obtained based on a 3d/slope.
The demonstrated sensing system thus proved to be highly se-
lective for glucose. The glucose analogues fructose, lactose,
and maltose were selected for control experiments.[4] The se-
lectivity is shown in Figure S2A in the Supporting Information.
Evidently, the absorbance hardly increased for these three ana-
As reported previously, V2O5 nanowires are capable of cata-
lyzing typical peroxidase reactions, using peroxidase substrates
such as ABTS in the presence of H2O2 to generate a green-col-
ored product.[9a] Initially, we evaluated the catalytic activity of
V2O5 nanowires at different pH values. Reactions were carried
out by incubating 0.02 mgmLÀ1 V2O5 nanowires with the sub-
strate ABTS (0.68 mm) and H2O2 (1 mm) at room temperature
in 10 mm NaOAc buffer of different pH values. As shown in
Figure 4A, V2O5 nanowires display their strongest intrinsic per-
oxidase-like activity towards ABTS at pH 4.0. Under the same
conditions (Figure 4B), V2O5-PDA showed better activity than
V2O5 nanowires owing to its good dispersion in aqueous solu-
tion. The slightly slower catalytic rate seen with V2O5-PDA-
AuNP may be due to partial blocking of the active sites of the
V2O5 nanowires by the attached AuNPs.
As AuNPs exhibit GOx-like activity at pH 7.0 whereas V2O5
nanowires show their strongest intrinsic HRP-like activity to-
wards ABTS at pH 4.0, mimicking of the enzyme cascade reac-
tion by the V2O5-PDA-AuNP composite material was performed
in two steps. 1) V2O5-PDA-AuNP was incubated for 30 min with
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ing of target DNA. We first attempted to investigate the influ-
ence of ssDNA on the catalytic activity of V2O5-PDA-AuNP
nanocomposites. V2O5-PDA-AuNP was first mixed with ssDNA
and then deployed for the cascade reaction as above. As
shown in Figure S2, the color change was found to be gradual-
ly attenuated as the concentration of ssDNA was increased,
suggesting effective suppression of the cascade reaction by
ssDNA as a result of its strong adsorption on the surface of
AuNPs. When the concentration of ssDNA was increased to
10 mm, the catalytic activity was completely suppressed. There-
fore, we chose 10 mm ssDNA, 50 mm glucose, and 0.5 mm
ABTS as the optimal conditions for complementary DNA (C-
DNA) detection.
Under the above-mentioned conditions, we evaluated the
capability of this enzyme-mimicking cascade reaction for the
quantitative detection of C-DNA. As shown in Figure 6A, the
Figure 5. (A) The time-dependent absorbance changes at 415 nm using
V2O5-PDA-AuNP as an artificial enzyme in the presence of different concen-
trations of glucose first in pH 7.0 NaOAc buffer (10 mm), incubated for
30 min at room temperature, and then adjusting to pH 4.0 by adding pH 4.0
NaOAc buffer (100 mm). (B) The relationship between absorbance at 600 s
(Abs600s) and concentration of glucose from 0 to 100 mm. The inset shows
a linear region versus the concentration of glucose from 0 to 10 mm.
logues, and the signal remained as low as the background.
Glucose concentrations in diluted blood and apple juice could
also be determined by this method (Figure S2B). According to
the calibration curve, the glucose concentration in the blood
sample was 4.36 mm, within the range of 3–8 mm for healthy
persons.
It has been reported previously that the GOx-like activity of
AuNPs is extremely sensitive to surface passivation.[16] As
shown in Scheme 2, single-strand DNA (ssDNA) strongly binds
to AuNPs, leading to effective suppression of their catalytic ac-
tivity, whereas double-strand DNA (dsDNA) binds only weakly
to AuNPs and thus only slightly perturbs their catalytic activi-
ty.[17] By taking advantage of this unique feature, we explored
the practicality of using our platform for the colorimetric sens-
Figure 6. (A) The time-dependent absorbance changes at 415 nm using
V2O5-PDA-AuNP as an artificial enzyme in the presence of different concen-
trations of C-DNA (ssDNA: 10 mm, glucose: 50 mm, ABTS: 0.5 mm). (B) The re-
lationship between absorbance at 600 s (Abs600s) and concentration of C-
DNA from 0 to 200 mm. The inset shows a linear region versus the concen-
tration of C-DNA from 0 to 0.10 mm.
absorbance at 415 nm gradually increased with increasing con-
centration of C-DNA, indicating that the formation of duplex
DNA could make ssDNA dissociate from the surface of the
AuNPs, thereby restoring their activity. Figure 6B shows a plot
of Abs600s versus concentration of C-DNA from 0 to 200 mm. A
good linear correlation (R2 =0.99) is observed over the concen-
tration range 0–0.10 mm and a detection limit of 2.3 nm was
determined based on a 3d/slope.
In a control experiment, we challenged AuNPs with a mixture
of ssDNA and a non-cognate DNA dT22. As shown in Figure 7A,
the absorption intensity was even lower than that with ssDNA
alone, suggesting that the sequence-specific formation of
duplex DNA was critical for regulating the catalysis of AuNPs.
Indeed, the additional non-cognate dT22 increased the cover-
age of DNA on the surface of the AuNPs, resulting in further
Scheme 2. Illustration of the GOx-like catalytic activity of AuNPs regulated
by DNA hybridization, resulting in suppression and restoration of mimicking
of the enzyme cascade reaction by the V2O5-PDA-AuNP composite material.
This mechanism underpins the colorimetric sensing of target DNA.
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ssDNA: TTT TTT CTT CTT CTC CTC CTT T; C-DNA: AAA GGA GGA
GAA GAA GAA GAA AAA A; control DNA: dT22; single-base mutat-
ed DNA: 1) AAA GGA GGA GTA GAA GAA GAA AAA A; 2) AAA GGA
GGA GCA GAA GAA GAA AAA A; 3) AAA GGA GGA GGA GAA GAA
GAA AAA A.
Instrumentation
UV/Vis spectra were recorded on a Jasco-V550 UV/Vis spectropho-
tometer. Fourier-transform infrared (FTIR) spectra were recorded on
a Bruker Vertex 70 FTIR spectrometer. Samples were prepared in
pellets using spectroscopic grade KBr. Thermogravimetric analysis
(TGA) was performed on a Rigaku Standard type analyzer at a heat-
ing rate of 108CminÀ1 from room temperature to 9008C. Scanning
electron microscopy (SEM) images were recorded using a Hitachi
S-4800 instrument (Japan). Transmission electron microscopy (TEM)
experiments were performed using a Philips Tecnai G2 20 S-TWIN
microscope operating at 200 kV. XPS measurements were per-
formed on an ESCALAB-MKII spectrometer (VG Co., United King-
dom) with AlKa radiation as the X-ray source for excitation.
Figure 7. (A) The time-dependent absorbance changes at 415 nm using
V2O5-PDA-AuNP as an artificial enzyme in the presence of 50 mm C-DNA and
50 mm dT22 (ssDNA: 10 mm, glucose: 50 mm, ABTS: 0.5 mm). (B) SNP detec-
tion in the presence of 200 mm C-DNA with “A” mutated to either T, C, or G.
deactivation of the catalysis. We then evaluated the selectivity
of this system for disease-associated single-nucleotide poly-
morphism (SNP) of DNA by testing its response to 200 mm C-
DNA with “A” mutated to either T, C, or G (Figure 7B).[5] A dif-
ference in signal could be discerned, thus indicating that this
method is sensitive and could detect SNP in DNA.
Synthesis of V2O5 nanowires
V2O5 nanowires were prepared by a hydrothermal method as de-
scribed elsewhere.[9a] Briefly, for the synthesis of V2O5 nanowires,
water-soluble vanadium(IV) oxosulfate (VOSO4) was oxidized with
potassium bromate (KBrO3) by stirring for 30 min at room tempera-
ture. After lowering the pH using nitric acid, the reaction mixture
was kept at 1808C for 24 h. After cooling to room temperature
and extensive washing, the dark-yellow precipitate was dried in an
oven at 808C overnight.
Conclusion
We have developed a facile method for fabricating V2O5-PDA-
AuNP nanocomposite with dual enzyme-mimetic activities. The
intrinsic HRP-like activity and GOx-like activity of the hybrid
material allowed the system to serve as a robust nanoreactor
for mimicking the complexities and functions of an enzymatic
cascade system. By taking advantage of these unique features,
this system has been further applied as a robust nanoprobe
for the detection of glucose as well as for the colorimetric
sensing of target DNA with high sensitivity and selectivity. Our
work is expected to provide new insights into the develop-
ment of enzyme mimics with versatile functionalities and reac-
tivities, a field that holds great promise, with potential applica-
tions in biocatalysis, bioassays, nano-biomedicine, and nano-
technology.
Synthesis of V2O5-PDA composite
V2O5 nanowires (20 mg) and dopamine (DA; 2 mg) were added to
10 mm Tris-HCl buffer (pH 8.0). The mixture was ultrasonicated for
2 h and then centrifuged. The collected solid was washed several
times with doubly-distilled water.
Synthesis of V2O5-PDA-AuNP composite
V2O5-PDA (5 mg) was dispersed in H2O (20 mL) with the aid of
ultrasonication. A 1 mm aqueous solution of HAuCl4 (50 mL) was
then added, ultrasonication was continued for 5 min, freshly pre-
pared NaBH4 solution (20 mL; 5 mg/200 mL H2O) was added, and
the mixture was further ultrasonicated for 10 min at room temper-
ature. It was then centrifuged and the collected solid was washed
several times with doubly-distilled water and then dissolved in H2O
(5 mL) to obtain a 1 mgmLÀ1 aqueous solution of V2O5-PDA-AuNP
composite material.
Experimental Section
Chemicals and materials
Vanadium(IV) oxosulfate and potassium bromate were purchased
from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). 2,2’-
Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) diammoni-
um salt was purchased from Sigma–Aldrich (St. Louis, MO, USA).
H2O2 was obtained from Beijing Chemicals Inc. (Beijing, China). Tet-
rachloroauric acid (HAuCl4·3H2O), sodium borohydride (NaBH4),
dopamine, and glucose were purchased from Alfa Aesar (USA). All
of these reagents were used as received without further purifica-
tion. Nanopure water (18.2 MW; Millipore Co., USA) was used in all
experiments.
Detection of glucose
V2O5-PDA-AuNP was first mixed with different concentrations of
glucose in pH 7.0 NaOAc buffer (10 mm) and incubated for 30 min
(V2O5-PDA-AuNP: 20 mgmLÀ1, glucose: 50 mm, ABTS: 0.5 mm) at
room temperature. The mixtures were then adjusted to pH 4.0 by
adding pH 4.0 NaOAc buffer (100 mm). The time-dependent ab-
sorbance changes at 415 nm were monitored by UV/Vis spectro-
photometry.
DNA oligomers were purchased from Sangon (Shanghai, China)
and used without further purification. Concentrations of these olig-
omers were determined by measuring the absorbance at 260 nm.
Extinction coefficients were estimated by the nearest-neighbor
method using mononucleotide and dinucleotide values. DNA se-
quences were as follows:
Detection of DNA
First, the influence of ssDNA on the enzyme cascade reaction was
studied. Different concentrations of ssDNA were added to solutions
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(containing V2O5-PDA-AuNP: 20 mgmLÀ1, glucose: 50 mm, ABTS:
0.5 mm) in pH 7.0 NaOAc buffer (10 mm) and incubated for 30 min
at room temperature. The mixtures were then adjusted to pH 4.0
by adding pH 4.0 NaOAc buffer (100 mm). The time-dependent ab-
sorbance changes at 415 nm were monitored by UV/Vis spectro-
photometry.
[4] Y. J. Song, K. G. Qu, C. Zhao, J. Ren, X. Qu, Adv. Mater. 2010, 22, 2206–
2210.
[5] Y. J. Song, X. H. Wang, C. Zhao, K. G. Qu, J. Ren, X. Qu, Chem. Eur. J.
2010, 16, 3617–3621.
[6] a) W. B. Shi, Q. L. Wang, Y. J. Long, Z. L. Cheng, S. H. Chen, H. Z. Zheng,
Y. M. Huang, Chem. Commun. 2011, 47, 6695–6697; b) X. H. Wang, K. G.
Qu, B. L. Xu, J. Ren, X. Qu, Nano Res. 2011, 4, 908–920.
[7] T. Pirmohamed, J. M. Dowding, S. Singh, B. Wasserman, E. Heckert, A. S.
Karakoti, J. E. King, S. Seal, W. T. Self, Chem. Commun. 2010, 46, 2736–
2738.
[8] a) Y. Jv, B. X. Li, R. Cao, Chem. Commun. 2010, 46, 8017–8019; b) M. Co-
motti, C. D. Pina, R. Matarrese, M. Rossi, Angew. Chem. 2004, 116, 5936–
5939; Angew. Chem. Int. Ed. 2004, 43, 5812–5815.
[9] a) R. Andrꢁ, F. Natꢂlio, M. Humanes, J. Leppin, K. Heinze, R. Wever, H.
Schrçder, W. Mꢃller, W. Tremel, Adv. Funct. Mater. 2011, 21, 501–509;
b) F. Natalio, R. Andrꢁ, A. F. Hartog, B. Stoll, K. P. Jochum, R. Wever, W.
Tremel, Nat. Nanotechnol. 2012, 7, 530–535.
[10] a) Y. Lin, Z. Li, Z. Chen, J. Ren, X. Qu, Biomaterials 2013, 34, 2600–2610;
b) X. He, L, Tan, D. Chen, X. Wu, X. Ren, Y. Zhang, X. Meng, F. Tang,
Chem. Commun. 2013, 49, 4643–4645.
For DNA detection, different concentrations of C-DNA were added
to solutions (containing V2O5-PDA-AuNP: 20 mgmLÀ1
, ssDNA:
10 mm, glucose: 50 mm, ABTS: 0.5 mm) in pH 7.0 NaOAc buffer
(10 mm) and incubated for 30 min at room temperature. The mix-
tures were then adjusted to pH 4.0 by adding pH 4.0 NaOAc buffer
(100 mm). The time-dependent absorbance changes at 415 nm
were monitored by UV/Vis spectrophotometry. Control experi-
ments and SNP detection were carried out using dT22 and single-
base mutated DNA, respectively, instead of C-DNA under the same
conditions.
[11] a) Q. Ye, F. Zhou, W. M. Liu, Chem. Soc. Rev. 2011, 40, 4244–4258; b) R.
Liu, S. M. Mahurin, C. Li, R. R. Unocic, J. C. Idrobo, H. J. Gao, S. J. Penny-
cook, S. Dai, Angew. Chem. 2011, 123, 6931–6934; Angew. Chem. Int. Ed.
2011, 50, 6799–6802.
[12] K. Qu, L. Wu, J. Ren, X. Qu, ACS Appl. Mater. Interfaces 2012, 4, 5001–
5009.
Acknowledgements
This work was supported by the 973 Project (2011CB936004,
2012CB720602) and the NSFC (21210002, 91213302).
[13] K. Qu, J. Ren, X. Qu, Mol. BioSyst. 2011, 7, 2681–2687.
[14] D. R. Dreyer, D. J. Miller, B. D. Freeman, D. R. Paul, C. W. Bielawski, Lang-
muir 2012, 28, 6428–6435.
[15] M. Sathiya, A. S. Prakash, K. Ramesha, J. M. Tarascon, A. K. Shukla, J. Am.
Chem. Soc. 2011, 133, 16291–16299.
Keywords: cascade reaction · detection · DNA recognition ·
enzyme mimicking
nanowire
· gold nanoparticle · sensors · V2O5
[16] W. J. Luo, C. F. Zhu, S. Su, D. Li, Y. He, Q. Huang, C. H. Fan, ACS Nano
2010, 4, 7451–7458.
[17] X. Zheng, Q. Liu, C. Jing, Y. Li, D. Li, W. Luo, Y. Wen, Y. He, Q. Huang, Y.
Long, C. Fan, Angew. Chem. 2011, 123, 12200–12204; Angew. Chem. Int.
Ed. 2011, 50, 11994–11998.
[1] a) R. Breslow, Acc. Chem. Res. 1995, 28, 146–153; b) G. Wulff, Chem. Rev.
2002, 102, 1–27; c) L. A. Levine, M. E. Williams, Curr. Opin. Chem. Biol.
2009, 13, 669–677; d) H. J. Yoon, C. A. Mirkin, J. Am. Chem. Soc. 2008,
130, 11590–11591.
[2] a) D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. 2005, 117, 8062–8083;
Angew. Chem. Int. Ed. 2005, 44, 7852–7872; b) C. Burda, X. B. Chen, R.
Narayanan, M. A. El-Sayed, Chem. Rev. 2005, 105, 1025–1102; c) H. Wei,
E. K. Wang, Chem. Soc. Rev. 2013, 42, 6060–6093.
Received: January 25, 2014
[3] L. Gao, J. Zhuang, L. Nie, J. Zhang, Y. Zhang, N. Gu, T. Wang, J. Feng, D.
Yang, S. Perrett, X. Yan, Nat. Nanotechnol. 2007, 2, 577–583.
Published online on && &&, 0000
&
&
Chem. Eur. J. 2014, 20, 1 – 7
www.chemeurj.org
6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
FULL PAPER
Towards artificial enzymes: A novel
nanocomposite consisting of V2O5 nano-
wires and Au nanoparticles (NPs) has
been constructed and used for an
&
Artificial Enzymes
K. Qu, P. Shi, J. Ren, X. Qu*
&& – &&
enzyme-mimicking cascade reaction,
whereby V2O5 and AuNPs display intrin-
sic peroxidase and glucose oxidase-like
activity, respectively (see scheme;
Nanocomposite Incorporating V2O5
Nanowires and Gold Nanoparticles for
Mimicking an Enzyme Cascade
Reaction and Its Application in the
Detection of Biomolecules
PDA=polydopamine, ABTS=2,2’-azino-
bis(3-ethylbenzothiazoline-6-sulfonic
acid). This system can be used for the
detection of glucose and as a nanoprobe
for colorimetric sensing of target DNA
with high sensitivity and selectivity.
Chem. Eur. J. 2014, 20, 1 – 7
www.chemeurj.org
7
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ