Simple and label-free fluorescence detection of ascorbic acid in rat brain microdialysates in the presence of catecholamines

Article abstract of DOI:10.1039/c7nj04574c

Ascorbic acid (AA), as one of the most important neurochemicals in cerebral systems, plays a vital role in many physiological and pathological processes. Herein, a facile, label-free, and ultrasensitive fluorescence sensing system was developed for the determination of AA based on the Ag⁺-o-phenylenediamine (OPD) interaction. OPD could be oxidized by Ag⁺ to generate fluorescent 2,3-diaminophenazine (OPDox). When AA was introduced, on the one hand, AA can inhibit the oxidation process due to its strong reducing capability. On the other hand, AA can be oxidized to dehydro-AA with an absorption peak at 380 nm, which has a good spectral overlap with the emission of OPDox. Thus, the inner filter effect (IFE) between dehydro-AA and OPDox may occur. Therefore, the introduction of AA can intensively suppress the fluorescence of the Ag⁺-OPD system. Benefitting from the remarkable synergistic effect of the reducing capability of AA and IFE, a facile and ultrasensitive sensor was constructed successfully for AA sensing. The whole detection procedure was achieved within 10 min. The linear response range of AA was obtained from 0.05 to 40 μM with a detection limit of 10 nM. This developed method has many merits including more simplicity, good selectivity, excellent biocompatibility, and more cost-effectiveness without using any nanomaterials. Notably, the proposed method was successfully applied to detect AA in rat brain microdialysates in the presence of catecholamines, thus providing a new route for AA detection in physiological and pathological fields.

Full text of DOI:10.1039/c7nj04574c

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PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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A simple and label-free fluorescence detection of ascorbic acid in
rat brain microdialysates in the presence of catecholamines
Received 00th January 20xx,
Accepted 00th January 20xx
a,b
a
a
b
c
a
a
Shuyun Zhu, *† Cuihua Lei, † Yue Gao, Jing Sun, Hongwei Peng, Han Gao, Ruixue Zhang,
a
a,b
a
Rui Wang, Xian-En Zhao *and Hua Wang *
DOI: 10.1039/x0xx00000x
Ascorbic acid (AA), as one of the most important neurochemical in cerebral systems, plays a vital role in many physiological
and pathological processes. Herein, a facile, label-free, and ultrasensitive fluorescence sensing system was developed for
www.rsc.org/
+
+
the determination of AA based on the Ag -o-phenylenediamine (OPD) interaction. OPD could be oxidized by Ag to
generate fluorescent 2,3-diaminophenazine (OPDox). When AA was introduced, on one hand, AA can inhibit the oxidation
process due to its strong reducing capability. On the other hand, AA can be oxidized to dehydro-AA with an absorption
peak at 380 nm, which has a good spectral overlap with the emission of OPDox. Thus, the inner filter effect (IFE) between
+
dehydro-AA and OPDox may occur. Therefore, the introduction of AA can intensively suppress the fluorescence of Ag -OPD
system. Benefited from the remarkable synergistic effect of reducing capability of AA and IFE, a facile and ultrasensitive
sensor was constructed successfully for AA sensing. The whole detection procedure was achieved within 10 min. The linear
response range of AA was obtained from 0.05-40 µM with a detection limit of 10 nM. This developed method enjoyed
many merits including more simplicity, good selectivity, excellent biocompatibility, and more cost-effective without using
any nanomaterials. Notably, the proposed method was successfully applied to detect AA in rat brain microdialysates in the
presence of catecholamines, thus providing a new route for AA detection in physiological and pathological fields.
8
,9
pathological importance and highly desired.
Up to now, some analysis methods have been implemented
1
. Introduction
1
0
to detect AA such as electrochemistry,
capillary
12
Monitoring the distribution of reactive species in living systems
is of great importance for understanding their physiological
functions and pathological effects, as well as early stage
diagnosis of some serious diseases. Ascorbic acid (AA) is one of
the most important neurochemicals in cerebral systems, which
plays a vital role in many physiological and pathological
1
electrophoresis, gas chromatography-mass spectrometry,
1
1
3
and high-performance liquid chromatography. Although
many approaches were well-established, the sophisticated
instrumentation, tedious sample preparation, and separation
procedures involved might limit their practical applications. To
resolve these problems, Mao’s group successfully developed
electrochemical methods for in vivo measurement of AA for
1
processes. Specifically, AA not only functions as an
antioxidant in the intracellular antioxidant system, but also
acts as a neuromodulator of both dopamine and glutamate-
1
4
the first time. Nevertheless, more simple but effective
measurement methods for AA in the cerebral systems are still
urgently desired.
2-5
mediated neurotransmission. Moreover, the level of AA is
related to some diseases; for instance, the lack of AA will result
in scurvy, and excessive intake of AA can lead to urinary stone,
Fluorescence detection systems are attracting a great deal
of interest as a quantitative analytical approach because of
their convenient operation, high sensitivity and selectivity, and
directly monitoring the target analytes of live cells, tissues, and
6
,7
diarrhea, and stomach convulsion. In this regard, the facile
and effective measurements of AA in the cerebral neuron
system of living animals are of great physiological and
1
5-17
even animals
without a complicated pretreated process
and instrumentation during the assay operations. Especially
with the development of nanoscience and nanotechnology,
various kinds of nanomaterials have been used as fluorescent
probes for the determination of AA. For instance, Tang’s group
designed cobalt oxyhydroxide (CoOOH)-modified persistent
luminescent nanoparticles (Sr
2 2 7
MgSi O : 1% Eu, 2% Dy) for the
determination and screening of AA in living cells and in vivo
1
based on the specific reaction of CoOOH. Lin’s group
8
3
designed Fe -functionlaized carbon quantum dots (CQDs)
+
3
based on the specific redox reaction between Fe and AA for
+
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1
9
the detection of AA in rat brain microdialysates. They also
synthesized tris(hydroxymethyl)-aminomethane-derived
carbon dots (CDs)-modified nanoflakes (tris-derivedCDs-
2
0
2
. Experimental
CoOOH) for monitoring cerebral AA in brain microdialysate.
Although these fluorescent nanoprobes displayed good
selectivity and sensitivity for the determination of AA in living
cells or microdialysates, they are complicated due to the time-
consuming synthesis procedure and complex post treatment
process. In addition, the detection of AA in biological matrices
may usually suffers from interferences by catecholamines
suchas dopamine (DA), norepinephrine (NE), L-levodopa (L-
DOPA), epinephrine (EP), 5-hydroxytryptamine (5-HT) and so
on. Therefore, it is necessary to develop new methods for the
determination of AA in the presence of catecholamines with
high selectivity and sensitivity.
2
.1 Reagents
Ascorbic acid (AA), dopamine (DA), AgNO
phenylenediamine (OPD), hydrogen peroxide (H ), ethylene
diamine tetraacetic acid (EDTA), Na HPO ·12H O, and
NaH PO ·2H were purchased from Aladdin Company
Shanghai, China). The uric acid (UA), tyrosine (Tyr), serine
Ser), glutamic acid (Glu), lysine (Lys), phenylalanine (Phe),
3
,
o-
2 2
O
2
4
2
2
4
2
O
(
(
arginine (Arg), glycine (Gly), epinephrine (EP), norepinephrine
(
NE), levodopa (L-DOPA), dopamine (DA), 5-hydroxytryptamine
5-HT), glutathione (GSH), homocysteine (Hcy), Cysteine (Cys),
(
and glucose were purchased from Alfa Aesar. Reduced N-
ethylmaleimide (NEM) was purchased from Sigma-Aldrich. 10
mM phosphate buffer solutions (PBS) were prepared by mixing
In this study, for the first time, we reported a rapid, simple,
and novel method for the highly sensitive and selective
detection of AA in rat brain microdialysates. As shown in
+
2 4 2 4
stock standard solutions of Na HPO and NaH PO . All reagents
Scheme 1, silver ions (Ag ), as the oxidase mimic, can catalyze
were of analytical reagent grade, and used as received. Doubly
deionized water was used throughout.
2.2 Apparatus
the oxidation of o-phenylenediamine (OPD) to form 2,3-
diaminophenazine
photoluminescence.
(OPDox)
showing
a
strong
2
1,22
AA exhibits high reducing capabilities
2
3
due to its hexose sugar acid with a γ-lactone structure, which All fluorescence measurements were carried out on an F-7000
could inhibit the generation of luminescent OPDox. Moreover, spectrometer (Hi-tachi, Japan) operated at an excitation
there is a good spectral overlap between the absorption wavelength at 417 nm. UV-vis spectra were recorded on a UV-
spectra of the yielding dehydro-AA and the emission spectra of vis spectrophotometer (Shimadzu, UV-3600, Japan). In vivo
OPDox, thus leading to the inner filter effect (IFE). Therefore, microdialysis sampling was accomplished by using a CMA 402
the introduction of AA could result in the remarkable decrease Syringe Pump (CMA, Solna, Sweden), a CMA 120 System (CMA,
+
of the fluorescence intensity of Ag -OPD system. Based on Solna, Sweden) for freely moving animals, a microdialysis
these facts, a simple and label-free fluorescent method has MAB6 probe (Stockholm, Sweden) which was perfused with
thus been developed for the detection of AA without the Ringer’s solution (5 mM) at a flow rate of 2.0 μL/min, and ASI
preparation of nanomaterials and the use of expensive stereotaxic flat skull coordinates (ASI Instruments Inc., MI,
instruments. Subsequently, the developed method was USA).
successfully applied to the direct analysis of AA in rat brain 2.3 Procedure for AA detection
microdialysates.
For the detection of AA, 15 µL of 6 mM OPD were diluted in
4
72 µL of PBS buffer (10 mM, pH 7.0), followed by the addition
of 8 µL of 6 mM AgNO , and then 5 µL of different
3
concentrations of AA. The samples were incubated for 10 min
in dark at room temperature before fluorescence
measurement. The selectivity of AA was explored in a similar
way by adding other interferences. The fluorescence spectra
were collected under excitation at 417 nm, and the slit
wavelengths of both excitation and emission were 5 nm,
respectively.
2
.4. Detection of AA in rat brain microdialysates
In vivo microdialysis experiments were performed as our
2
4,25
previous work.
Briefly, the rats were anesthetized with
2
0% urethane (1.2 g/kg, i.p.) before probe implantation
surgery, and remained anesthetized throughout the
experimental period. The rat’s body temperature was
maintained at 37
℃ during the experimental procedure. A
pretreated probe was inserted into the right striatum with
stereotaxic flat skull coordinates: A: + 1.0 mm from bregma, L:
Scheme 1 Schematic illustration of the strategy of facile
±
2.9 mm from midline and H: -3.5 mm from dura. Animals
ascorbic acid sensing.
were awake and freely moving with access to food and water
throughout the experiment. Next, the brain microdialysis
2
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probe (MAB6) was perfused with artificial cerebrospinal fluid the occurrence of inner filter effect (IFE). Ascribed to the two
a CSF) (126 mM of NaCl, 27.5 of mM NaHCO , 2.4 mM of KCl, reasons, the significant enhancement in the fluorescence along
.1 mM of CaCl , 0.85 mM of MgCl , 0.5 mM of Na SO , 0.5 with the oxidative reaction of OPD could be partially
mM of KH PO , pH =7.0) at a rate of 2.0 µL/min using a suppressed in the presence of AA.
microinjection pump (CMA 402, Sweden) and microsyringe
CMA, 1.0 mL) for 90 min to reach baseline values. Finally,
(
3
1
2
2
2
4
2
4
(
every 50 µL of microdialysate was collected for the following
AA sensing.
3
. Results and discussion
3
.1. Design and establishment of AA sensing system
As shown in Fig. 1, the aqueous solution of OPD has always
remained colorless and exhibited negligible fluorescence
+
(curve and vial 1). In contrast, the introduction of Ag
essentially triggers the oxidative reaction of OPD, during which
the original colorless and non-fluorescent solution gradually
turned to pale yellow in color and showed intense orange-
yellow fluorescent under ultraviolet (curve and vial 2). As
+
shown in Fig. 1A, the Ag -OPD mixed solution has an obvious
absorption peak at about 417 nm, which belongs to the
characteristic absorption spectrum of OPDox, the main
2
6
oxidation product of OPD. Meanwhile, the corresponding
emission spectrum in Fig. 1B exhibited a peak at about 557
nm, which is similar to that of OPDox in previous work as
Fig. 1 Absorbance (A) and fluorescence emission spectra (B) of
+
+
the OPD (1), OPD + Ag (2), and OPD + Ag + AA in PBS buffer at
pH 7.0. The corresponding photographs under visible (C) and
2
7,28
+
ultraviolet light (D). The final concentrations of OPD, Ag , and
well.
Then, both the absorption intensity at 417 nm and
the fluorescence intensity at 557 nm decreased obviously after
the addition of AA (curve and vial 3).
AA are 180 μM, 96 μM, and 30 μM, respectively.
In order to verify the sensing mechanism, the addition
+
sequence of AA was investigated. As shown in Fig. S1, Ag
Catecholamines, as common interferences, usually coexist in
the biological fluids with AA. Therefore, we investigated the
influences of catecholamines including DA, EP, NE, L-DOPA,
could oxidize OPD to generate OPDox with a strong
+
2
fluorescence (curve a). According to the previous report, Ag
1
+
and 5-HT on the fluorescence responses of Ag -OPD system. As
was reduced to zero-valent silver and formed silver
nanoparticles (AgNPs). Actually, the formed nanoparticles
were observed on a membrane layer by TEM analysis (Fig.
S2A). To confirm the components that might comprise such
nanoparticles, the thus-formed nanoparticles were
characterized by energy-dispersive spectroscopy (EDS) analysis.
As shown in Fig. S3, the element comprised in the
nanoparticles was silver. These results indicated the formation
shown in Fig. S5, the fluorescence intensity decreases up to
8
0% at 30 μM AA. In contrast, the presence of 30 μM
catecholamines resulted in fluorescence quenching less than
2
4
0%. Similarly, the decrease degrees of absorption intensity at
17 nm in the presence of catecholamines were less than that
of AA. Besides, no new absorption peak was observed after the
addition of catecholamines. These results indicated AA
possesses higher inhibition ability for the fluorescence
+
of AgNPs could occur during the reaction of Ag and OPD. After
+
AA was added into the Ag -OPD mixed solution, the
+
intensity of Ag -OPD system due to the synergistic effect of
stronger reducibility of AA and the IFE. Therefore, a convenient
fluorimetric assay could be designed for sensing AA sensitively
and selectively.
fluorescence intensity of the solution decreased remarkably
(curve b), indicating AA could reduce fluorescent OPDox into
non-fluorescent OPD. It has also been reported that AA was
2
9
common reducing agent for the synthesis of AgNPs. So, AA
3.2. Optimization of the sensing system
+
was reacted firstly with Ag for 5 min followed by the addition
The reaction conditions were optimized to establish the
optimum analytical conditions. pH is a crucial factor for almost
every sensing system. Fig. 2A shows the fluorescence intensity
of OPD. As shown in curve c of Fig. 1S, the fluorescence
intensity of the solution decreased furtherly. Moreover, the
formed AgNPs exhibited different size and morphology (Fig.
+
of Ag -OPD system in the presence and absence of AA under
+
the media of different pH values. The fluorescence intensity
showed the largest difference when the pH was around 7.0. In
the strong acidic medium, the amino groups of OPD could be
S2B). The results indicated that AA was also responsive to Ag .
Therefore, the presence of AA inhibited the generation of
OPDox due to its strong reducibility towards both OPDox and
+
Ag . More interestingly, a new absorption peak generated at
+
protonated, which could inhibit the oxidation by Ag . When
+
the pH value was higher than 7.0, Ag might be more prone to
380 nm from the yielding dehydro-AA had a good overlap with
hydrolysis, which could decrease its oxidization ability.
excitation spectrum of fluorescent OPDox (Fig. S4), resulting in
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Moreover, the pH 7.0 was established to fit for enzyme concentration ranges of 0.05-1.0 μM and 1.0-40 μM. The
mimetic reaction. Therefore, pH 7.0 was the optimal condition regression equations were ΔF = 13.88 + 28.39 CAA (μM)
2
2
for the sensing system.
(R =0.995) and ΔF = 42.56 + 6.147 CAA (μM) (R =0.997),
respectively. The detection limit can reach as low as 10 nM
estimated by a signal to noise of 3. Moreover, the analysis
repeatability of the proposed method was evaluated by six
repeated measurements of 0.5 μM and 5.0 μM AA and the
relative standard deviation (RSD) was 3.61% and 2.37%,
respectively, demonstrating the reliability of the proposed
method.
In addition, we compared the characteristics of the
proposed sensor with other fluorescent AA sensors reported
elsewhere. As shown in Table 1, this proposed system could
provide better detection sensitivity in comparison with those
3
0
of other fluorescent nanoprobes including gold nanoclusters,
3
carbon quantum dots (CQDs), graphitic carbon nitride
3
nanosheets, copper nanoclusters, and graphene quantum
1
2
33
2
3
dots (GQDs). Moreover, this developed fluorimetric method
is relatively simple and fast, of which the whole detection
procedure can be finished within 10 min. In contrast, the
fluorescent nanomaterials may entail much longer reaction
time to prepare by using the complicated synthesis and post-
treatment process.
Fig. 2 Effect of pH (A) and reaction time (B) on the
fluorescence intensity at 557 nm in the absence (■) and
presence (●) of 40 μM AA. Other conditions are the same as
that in the Fig. 1.
The effect of reaction time on the detection of AA was also
studied, and the experimental results were shown in Fig. 2B.
+
The results indicated that the fluorescence of Ag -OPD system
increased gradually and reached about 90% of the maximum
when the reaction time reached 10 min, showing that the
oxidation reaction was almost complete in 10 min. While in
the presence of AA, the fluorescence decreased quickly in the
first 1 min, and then remained almost constant in the following
2
0 min. Thus, the optimum time for the proposed system was
set as 10 min.
.3. Sensitivity of the sensing system
3
Under the optimization conditions, we evaluated the analysis
capability of this system for the quantitative detection of AA.
As shown in Fig. 3A, it was clearly seen that with the increase
+
of AA concentrations, the fluorescence intensities of Ag -OPD
+
Fig. 3 (A) Fluorescence spectra of the Ag -OPD solution in the
system decreased gradually while the ΔF=F -F increased
0
presence of varied concentrations of AA (0-40 μM). (B)
Relationship between ΔF and the concentrations of AA. Inset:
relationship between ΔF and the lower concentrations of AA.
systematically, where F and F are fluorescence intensities at
0
557 nm in the absence and presence of AA, respectively. The
ΔF exhibited a good linear relationship with AA in the two
4
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AA sensing by employing NEM as an effective GSH, Hcy, and
Cys scavenger.
Table 1 Comparison of the detection performances for AA
among different probes.
Probes/Ref.
Linear
range
Detection
limit (μM)
Synthesis
time for
probes
(μM)
Protein-modified Au 1.5-10
nanoclusters/[30]
0.2
24 h
Phosphorus/nitrogen
dual-doped
5-200
1.35
72 h
24 h
a
CQDs /[31]
Graphitic
nitride
nanosheets/[32]
carbon 0.5-200
0.13
Cu nanoclusters/[33]
b
GQDs /[23]
0.5-10
0.11
0.28
0.05
6 h
0.5-250
28 h
Hexagonal
cobalt 0.1-20
40 min
oxyhydroxide-carbon
dots/[34]
CdS QDs/[35]
+
Ag -OPD/ This work
0.06-0.3
0.05-1.0
0.002
0.01
1 h
10 min
1
.0-40
a
carbon quantum dots
b
+
Fig. 4 (A) The selectivity of Ag -OPD system towards different
graphene quantum dots
+
.4. Selectivity of Ag -OPD system with different ions and
3
metal ions. The concentration of AA is 40 μM, and the
concentration of all the metal ions are 400 μM. (B) The
biological molecules
+
selectivity of Ag -OPD system towards other biological
To evaluate the specificity of the developed assay for AA,
several potential interfering compounds were investigated
under the same conditions. Firstly, various metal ions including
molecules. The concentration of AA is 40 μM, and the
concentrations of UA, DA, L-DOPA, NE, and EP are 5 μM,
respectively. The concentrations of other interfering species
are 40 μM. The NEM concentration is 0.3 mM.
+
2+
2+
2+
+
2+
2+
2+
2+
K , Ca , Zn , Mg , Na , Mn , Ba , Co , and Cu containing
+
Ag -OPD system were measured under 417 nm excitation. As
demonstrated in Fig. 4A, these potential metal ions caused no
significant signal fluctuations, indicating they showed
+
negligible influence on the fluorescence intensity of Ag -OPD
3
.5. Application of the proposed sensing system to rat brain
microdialyates analysis
Recently, AA has been proven to be a kind of neuro molecules,
thus monitoring the levels of AA in brain microdialysates are
important for the research of physiology, pathology, and
clinics. In our experiment, an unknown amount of AA in a rat
brain microdialysis sample was estimated by using the
standard addition method with 0.5 μM AA solution. As shown
system.
Usually the concentration of catecholamines in biological
fluids are much lower than that of AA. Thus, the selectivity of
+
Ag -OPD system was further validated by comparing the signal
changes of samples containing the lower concentrations of
catecholamines and other common biological molecules. As
shown in Fig. 4B, except for GSH, Hcy, and Cys, the response of
+
in Fig. 5, the fluorescence spectra of Ag -OPD system were
+
recorded in the absence (a) and presence of 50 μL rat brain
microdialysates (b). Next, 5 μL 50 μM AA standard solution
was added twice (curve c and d, Fig. 5). According to the
standard method, the concentration of AA was calculated to
be 5.96 μM in the rat brain microdialysates, which is consistent
Ag -OPD system was selective toward AA. Because GSH, Hcy,
and Cys could also have somewhat reducing abilities towards
+
Ag , their addition resulted in the decrease of the
fluorescence. However, N-ethylmaleimide (NEM), a scavenger
that can exclusively react with sulfhydryl compound, could
3
7
3
effectively eliminate the interference. As can be seen from
6
with the previous reports.
+
Fig. 4B, after incubation of GSH, Hcy, or Cys with NEM, the Ag -
OPD system did not generate obvious fluorescence decrease,
whereas the determination of AA was not affected by the
+
introduction of NEM. Therefore, the Ag -OPD system could
present a sensitive and selective fluorescent approach toward
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3
4
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Fig. 5 Fluorescence spectra of Ag -OPD system for AA
+
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In summary, a novel fluorescent assay was developed for the 17 X. E. Zhao, C. H. Lei, Y. Gao, H. Gao, S. Y. Zhu, X. Yang, J. M.
You and H. Wang, Sens. Actuators B: Chem., 2017, 253, 239.
facile detection of AA based on the synergistic effect of
+
reducing ability of AA and IFE. The Ag -OPD probing system
18 N. Li, Y. Li, Y. Han, W. Pan, T. Zhang and B. Tang, Anal. Chem.,
014, 86, 3924.
1
2
9 L. B. Li, C. Wang, J. X. Luo, Q. W. Guo, K. Y. Liu, K. Liu, K. Liu,
W. J. Zhao and Y. Q. Lin, Talanta, 2015, 144, 1301.
features some excellent chemical properties such as high
water solubility and strong fluorescence intensity, which could
be served as a novel fluorescence probe for AA sensing. 20 L. B. Li, C. Wang, K. Y. Liu, Y. H. Wang, K. Liu and Y. Q. Lin,
Anal. Chem., 2015, 87, 3404.
Moreover, no nanomaterials participated in the assays, making
2
2
1 X. Yang and E. K. Wang, Anal. Chem., 2011, 83, 5005.
2 H. C. Dai, P. J. Ni, Y. J. Sun, J. T. Hu, S. Jiang, Y. L. Wang and Z.
Li, Analyst, 2015, 140, 3616.
it a simple, cost-effective, fast, and lowly laborious candidate.
More importantly, this fluorimetric method was successfully
applied to the determination of AA in rat brain microdialysates 23 F. P. Shi, Y. Zhang, W. D. Na, X. Y. Zhang, Y. Li and X. G. Su, J.
samples, providing a potential platform for AA monitoring
from many other biological samples.
Mater. Chem. B, 2016, 4, 3278.
4 Y. R. He, X. E. Zhao, S. Y. Zhu, N. Wei, J. Sun, Y. B. Zhou, S. Liu,
Z. Q. Liu, G. Chen, Y. R. Suo and J. M. You, J. Chromatogr. A,
2
2
016, 1458, 70.
5 X. E. Zhao, Y. R. He, P. Yan, N. Wei, R. J. Wang, J. Su, L. F.
Zheng, S. Y. Zhu and J. M. You, RSC Adv., 2016, , 108635.
6 S. S. Ma, Q. Y. Zhou, F. Y. Mu, Z. H. Chen, X. Y. Ding, M. Zhang
and G. Y. Shi, Analyst, 2017, 142, 3341.
7 J. Sun, B. Wang, X. Zhao, Z. J. Li and X. R. Yang, Anal. Chem.,
2
2
2
Conflicts of interest
6
There are no conflicts to declare.
2
28 R. Li, C. H. Lei, X. E. Zhao, Y. Gao, H. Gao, S. Y. Zhu and H.
016, 88, 1355.
Acknowledgements
Wang, Spectrochim. Acta A, 2018, 188, 20.
9 S. P. Wu and S. Y. Meng, Mater. Chem. Phys., 2005, 89, 423.
0 X. Wang, P. Wu, X. Hou and Y. Lv, Analyst, 2013, 138, 229.
This work is kindly supported by the National Natural Science
Foundation of China (Nos. 21405094, 21775088, and
2
3
21675099), the Open Funds of the State Key Laboratory of 31 X. J. Gong, Y. Liu, Z. H. Yang, S. M. Shuang and Z. Y. Zhang,
Electroanalytical Chemistry (No. SKLEAC201506), the Natural
Science Foundation of Qinghai Province (2016-ZJ-955), the
Development Project of Qinghai Key Laboratory (No. 2017-ZJ-
Y10), the National Undergraduate Research Training Program
Anal. Chim. Acta, 2017, 968, 85.
3
3
2 M. C. Rong, L. P. Lin, X. H. Song, Y. R. Wang, Y. X. Zhong, J. W.
Yan, Y. F. Feng, X. Y. Zeng and X. Chen, Biosensor.
Bioelectron., 2015, 68, 210.
3 H. B. Rao, H. W. Ge, Z. W. Lu, W. Liu, Z. Q. Chen, Z. Y. Zhang,
X. X. Wang, P. Zou, Y. Y. Yang, H. He and X. Y. Zeng,
Microchim. Acta, 2016, 183, 1651.
(No. 201610446033, 2017A029), and the Scientific Research
Foundation of Qufu Normal University (No. BSQD201203) .
3
3
4 L. B. Li, C. Wang, K. Y. Liu, Y. H. Wang, K. Liu and Y. Q. Lin,
Anal. Chem., 2015, 87, 3404.
5 M. Ganiga and J. Cyriac, Anal. Bioanal. Chem., 2016, 408
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Notes and references
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New Journal of Chemistry
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DOI: 10.1039/C7NJ04574C
Graphical Abstract
A simple and label-free fluorescence detection of ascorbic acid in rat brain
microdialysates in the presence of catecholamines
a,b
a
a
b
c
a
Shuyun Zhu * †, Cuihua Lei †, Yue Gao , Jing Sun , Hongwei Peng , Han Gao , Ruixue
a
a
a,b
a
Zhang , Rui Wang , Xian-En Zhao *, Hua Wang *
A facile and ultrasensitive sensor was constructed successfully for AA sensing based on the
synergistic effect of reducing capability of AA and IFE.