A novel molecularly imprinted polymer on CdSe/ZnS quantum dots for highly selective optosensing of mycotoxin zearalenone in cereal samples

Article abstract of DOI:10.1039/c3ra45172k

A novel molecularly imprinted optosensing material (MIOM) based on ionic liquid (IL)-stabilized CdSe/ZnS quantum dots (QDs) was prepared, for highly selective and sensitive recognition of the mycotoxin zearalenone (ZON). ZON is expensive and highly toxic, so the ZON analog cyclodo-decanyl-2,4- dihydroxybenzoate (CDHB) was instead used as the template. MIOM was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and adsorption experiment. Under optimal conditions, the relative fluorescence intensity of MIOM decreased linearly with increasing ZON concentration, in the range of 0.003-3.12 μmol L^-1. MIOM had a detection limit of 0.002 μmol L^-1. MIOM was used to detect ZON in corn, rice and wheat flours, and at three concentration levels 50, 100 and 500 ng g^-1, ZON recoveries for these three cereals were 94.2-98.7%, 93.1-107.6% and 84.4-106.0%, respectively.

Full text of DOI:10.1039/c3ra45172k

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A novel molecularly imprinted polymer on CdSe/
ZnS quantum dots for highly selective optosensing
of mycotoxin zearalenone in cereal samples†
Cite this: RSC Adv., 2014, 4, 2764
*
Guozhen Fang, Chao Fan, Huilin Liu, Mingfei Pan, Huidan Zhu and Shuo Wang
A novel molecularly imprinted optosensing material (MIOM) based on ionic liquid (IL)-stabilized CdSe/ZnS
quantum dots (QDs) was prepared, for highly selective and sensitive recognition of the mycotoxin
zearalenone (ZON). ZON is expensive and highly toxic, so the ZON analog cyclodo-decanyl-2,4-
dihydroxybenzoate (CDHB) was instead used as the template. MIOM was characterized by scanning
electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and adsorption experiment.
Under optimal conditions, the relative fluorescence intensity of MIOM decreased linearly with increasing
Received 17th September 2013
Accepted 26th November 2013
ZON concentration, in the range of 0.003–3.12 mmol Lꢀ1. MIOM had a detection limit of 0.002 mmol Lꢀ1
.
MIOM was used to detect ZON in corn, rice and wheat flours, and at three concentration levels 50, 100
and 500 ng gꢀ1, ZON recoveries for these three cereals were 94.2–98.7%, 93.1–107.6% and 84.4–
106.0%, respectively.
DOI: 10.1039/c3ra45172k
www.rsc.org/advances
sensors, and mass balances sensors.8 The major challenges in
developing MIP-based sensors include three following respects,
Introduction
poor and moderate affinities and selectivities, limited polymer
formats, and integrating MIP with a signaling platform.9 The
imprinting process generates different types of binding sites,
and only a small part has highly affinity and selectivity for the
template. MIPs have poor selectivities at high analyte concen-
trations, because of the dominance by the more numerous low-
affinity sites, and have low binding capacities at low analyte
concentrations, because of the template leaching. To improve
MIPs affinities and selectivities, the functional monomers
selection and the effective template removal are crucial.10 In
addition, there have been some methods reported about inte-
grating MIPs with signaling platforms, including the electro-
polymerization of MIPs on conducting surfaces, and the
physical adsorption of MIPs on nonconducting surfaces.11
Photoluminescent semiconductor quantum dots (QDs) have
received much attention over the past few decades. QDs
advantages over conventional organic uorescent dyes include
high photoluminescence yields, size-dependent emission
wavelengths and high photochemical stabilities. Bruchez et al.
reported the rst biological analysis using QDs, demonstrating
the use of QDs as biological probes within living organisms,12
QDs have since been applied as uorescent labels for the
detection of small molecules, biomolecules and ions.13
QD-based sensors have also received much attention.14 Meng
et al. developed a simple, fast and sensitive biosensor consisting
of enzymes, QDs and acetylcholine for detecting organophos-
phorus pesticides in real samples.15 Ji et al. reported a novel
biosensor for detecting paraoxon, by coupling organophos-
phorus hydrolase to CdSe/ZnS QDs.16 This was achieved
Molecular imprinting is used to synthesize polymers with
special binding sites closely matching the template. Wulff and
Sarchan prepared the rst molecularly imprinted polymer
(MIP).1 Mosbach et al. reported molecular imprints of theoph-
ylline and diazepam in 1993, which greatly promoted the
development of MIPs.2 MIPs have advantages to biological
antibodies and other recognition materials, such as their tail-
orable recognition properties, high selectivity, long life cycles,
ease of preparation and low cost.3 MIPs also exhibit higher
stabilities against high temperatures, harsh chemical environ-
ments, and extreme pH values. The recognition structures of
MIPs can be synthesized as required.4 These advantages benet
MIPs application in chromatographic separation,5 solid-phase
extraction6 and biomimetic sensor.7 MIP-based sensors have
been developed, including uorescent sensors, optical sensors,
colorimetric and radiometric binding assays, electrochemical
Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin Key
Laboratory of Food Nutrition and Safety, Tianjin University of Science and
Technology, Tianjin 300457, China. E-mail: s.wang@tust.edu.cn; Fax: +86 22
60601332; Tel: +86 22 60601430
† Electronic supplementary information (ESI) available: Fig. S1: UV-vis spectra of
the extracts from Soxhlet extraction of MIOM (a) and NIOM (b), and UV-vis spectra
of CDHB (c), Fig. S2: FT-IR spectra of CDHB, Fig. S3: 1H NMR (A) and 13C NMR
spectra (B) of CDHB, Fig. S4: negative ion mass spectra of CDHB, Fig. S5:
uorescence emission spectra of NIOM (a), MIOM before (c) and aer (b)
template extraction, Fig. S6: uorescence emission spectra of MIOM (b), NIOM
(a), MIOM with addition of 1.56 mmol Lꢀ1 CDHB (d) and NIOM with addition of
1.56 mmol Lꢀ1 CDHB (c) in acetonitrile (A), methanol (B) and ethanol (C),
separately. See DOI: 10.1039/c3ra45172k
2764 | RSC Adv., 2014, 4, 2764–2771
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through the electrostatic interaction of negatively charged QDs stored at 4 ꢁC. ZON, ochratoxin A (OTA) and deoxynivalenol
surfaces with positively charged protein side chain and terminal (DON) were obtained from Fermentek (Australia).
groups, and the detection limit was about 10ꢀ8 mol Lꢀ1
.
Corn, rice and wheat ours were purchased from a super-
Incorporating uorescent QDs as a signaling platform, and market (Tianjin, P.R. China) and ZON-free samples were
selective MIPs as a recognition material, yield optical sensors detected by high-performance liquid chromatography-mass
for target analyte recognition. The MIP would bind the analyte, spectrometry (HPLC-MS).
and the QDs uorescence intensity would change according to
the concentration of the bound analyte. Analyte concentrations
can then be converted into optical signals and detected directly
by spectrouorometry.17 Zhang et al. reported a CdSe QD-based
MIP-coated composite, for the selective recognition of cyto-
chrome c.18 Ye et al. used a single-bath strategy to synthesize
CdTe@SiO2@MIP for recognizing 4-chlorophenol.19
Instruments and measurements
1H and 13C NMR spectra were recorded on a NMR spectrometer
(Bruker BioSpin, Switzerland). Fluorescence measurements
were recorded on a Lumina spectrouorometer (Thermo, USA)
equipped with a 1 ꢂ 1 cm quartz cell. Ultraviolet-visible (UV-vis)
absorption spectra was recorded from 200 to 800 nm, on an
Evolution 300 spectrophotometer (Thermo, USA). Fourier-
transform infrared (FT-IR) spectra was recorded from 4000 to
400 cmꢀ1 using a Tensor 27 FT-IR spectrophotometer (Bruker,
Germany). Scanning electron microscopy (SEM; SU1510; Hita-
chi, Japan) was used to observe the size, shape and surface
morphology of MIOM.
In the current study, the mycotoxin zearalenone (ZON) was
used as a target analyte, to illustrate the usefulness of the
proposed optical sensor. ZON, also known as F-2 toxin, is
mainly produced by Fusarium fungi, and contaminates cereal
crops such as corn, barley, sorghum, wheat and oats.20 ZON
causes reproductive problems, infertility in farm animals, and
estrogenic effects and possible carcinogenicity in humans.21
Many countries have regulated acceptable ZON limits in cereals.
Austria has established a maximum wheat ZON limit of
Synthesis of cyclododecyl 2,4-dihydroxybenzoate (CDHB)
60 mg kgꢀ1 22 and the European Union maximum ZON limits for CDHB was synthesized using a modied reported method.24
,
unprocessed maize and unprocessed cereals are 350 and Specically, 1,10-carbonyldiimidazole (10 mmol) was mixed with
100 mg kgꢀ1 respectively.20 Various analytical methods have 2,4-dihydroxybenzoic acid (10 mmol) in anhydrous DMF
been developed to assay ZON in complex samples including (20 mL). The mixture was stirred at 40 ꢁC in a water bath for 3 h
high-performance liquid chromatography (HPLC), uorophore- under a N2 atmosphere. Cyclododecanol (10 mmol) and DBU
linked immunosorbent assay (FLISA), and ultra high pressure (10 mmol) were added, and the mixture was stirred for 24 h
liquid
(UPLC-MS/MS).5,20,23
Herein,
chromatography
tandem
mass
spectrometry under N2. 20 mL of CH2Cl2 and 20 mL of water were added to
the solution. The organic phase was separated and washed with
a
molecularly imprinted optosensing material 10% (v/v) HCl (3 ꢂ 30 mL), and saturated NaCl (2 ꢂ 30 mL),
(MIOM) is prepared, using a ZON analog as a template. MIOM is then dried over anhydrous Na2SO4. CDHB was puried through
based on ionic liquid (IL)-stabilized CdSe/ZnS (QDs), and is rst a silica gel column, with a petroleum ether–ethyl acetate (6 : 1)
used for the detection of ZON. The characterization of MIOM eluent. The removal of solvent at 50 ꢁC, yielded CDHB as a white
was described and discussed in detail.
solid powder.
Preparation of MIOM
Experimental
Materials
CdSe/ZnS QDs (0.05 mmol) and IL (3.0 mmol) were dissolved in
chloroform (5.5 mL). The template CDHB (1.0 mmol) and MAA
(4.0 mmol) were added, and the solution was stirred for 30 min
at room temperature. EGDMA (5.0 mmol) and AIBN (20 mg)
were added, and the mixture was purged with N2 for 5 min to
remove any oxygen. The mixture was stirred at 55 ꢁC in a water
bath for 24 h in the dark, to allow polymerization. The template
was extracted by accelerated solvent extraction (ASE), under the
conditions shown in Table 1. Polymers were transferred to a
ask for Soxhlet extraction with 4 : 1 (v/v) methanol–acetonitrile
until CDHB had been completely removed. Polymers were dried
under vacuum at 60 ꢁC for 10 h. Non-imprinted optosensing
material (NIOM) was prepared similarly, but in the absence of
CDHB.
1,10-Carbonyldiimidazole, 2,4-dihydroxybenzoic acid, cyclo-
dodecanol, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and
dimethyl formamide (DMF) were obtained from Aladdin
(Shanghai, P.R. China). CdSe/ZnS QDs with a uorescence
emission wavelength of 562 nm were purchased from Jiayuan
(Wuhan, P.R. China). The 1-vinyl-3-octylimidazolium hexa-
uorophosphate IL was purchased from the Chinese Academy
of Sciences (Lanzhou, P.R. China). MIOM was prepared using
the functional monomer methacrylic acid (MAA; 99%, Tianjin
Chemical Reagent Research Institute, Tianjin, P.R. China),
cross-linker ethylene glycol dimethacrylate (EGDMA; 98%,
Sigma-Aldrich, St Louis, MO, USA) and initiator 2,2-azobisiso-
butyronitrile (AIBN; 99%, Tianjin Kermel Chemical Reagents
Co., Ltd., Tianjin, P.R. China). DMF and MAA were distilled
Fluorescence measurements
under reduced pressure before use. EGDMA was extracted with The uorescence detection of MIOM and NIOM was carried out
10% NaOH, dried over anhydrous MgSO4, and distilled under under the same conditions. The excitation and emission slit
reduced pressure. AIBN was recrystallized from ethanol, and widths were both 5 nm. The excitation wavelength was 280 nm,
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Table 1 ASE conditions for CDHB
hydrophobic. Taking into account the negatively charged QDs,
the surface of CdSe/ZnS QDs was modied by electrostatic
interaction with positively charged IL. IL provided C]C bonds
for the QDs to connect with the MIP, and also improved the
uorescence stability of CdSe/ZnS QDs. MAA interacted with IL
through the C]C bonds, and the MAA carboxyl group hydrogen
bonded with the phenolic hydroxyl groups of CDHB, thus
‘pushing’ the template into the polymer. Removing the
template yielded cavities with shape and functionality comple-
mentarity to CDHB, and thus yielded the MIOM.
To demonstrate CDHB was completely removed, we detected
UV-vis adsorption of CDHB, and the extracts from Soxhlet
extraction. Fig. S1† shows that there were no UV adsorption
peaks at 259 and 298 nm in the UV-vis spectra of the extracts,
which are the characteristic peaks of the template. The UV-vis
spectra of the extracts of MIOM and NIOM were comparable,
indicated that the template had been completely removed.
Extraction solvent
MeOH–ACN (4/1) (v/v)
Pressure (psi)
1500
60
10
10
60
60
3
Temperature (ꢁC)
Heat-up time (min)
Static time (min)
Flush volume (%)
Purge time (s)
Number of cycles
Cell volume (mL)
Number of extractions
66
2
and emission was recorded at 500–600 nm. The photomultiplier
tube voltage was 350 V.
Rebinding, selectivity and competitive adsorption
experiments
Characterization of CDHB and MIOM
To evaluate the binding capability of MIOM, 1 mg of MIOM or
NIOM was dispersed in 3 mL of certain concentrations of CDHB
or ZON. CDHB concentration was 0 to 31.2 mmol Lꢀ1 in the
adsorption equilibrium experiment. ZON concentration was
1.562 mmol Lꢀ1 in the adsorption kinetic experiment,
0.936 mmol Lꢀ1 in selective and competitive adsorption experi-
ments. Selectivity and competitive adsorption experiments were
carried out using ZON, OTA and DON. OTA and DON are also as
mycotoxins in cereals. The mixture was mechanically agitated
for a certain time before measurement. The adsorption times
were 0 to 8 h in the adsorption kinetic experiment, 7.5 h in the
adsorption equilibrium experiment, selective and competitive
adsorption experiments.
CDHB was characterized by yield, melting point, UV absorp-
tions, IR absorptions, NMR spectra and mass spectra. Speci-
max
ꢁ
cally: CDHB (2.2 g, 69%), m.p. 57–59 C, labs (MeOH)/nm 259
(3/dm3 molꢀ1 cmꢀ1 17 411), 298 (6724). FT-IR spectra (Fig. S2†),
nmax/cmꢀ1 3383 (O–H), 2945 (saturated C–H), 1652 (aromatic
C]C), 1519 (aromatic C]C), 1473 (aromatic C]C), 1278 (C–O),
844 and 785 (aromatic C–H). 1H and 13C NMR spectra of CDHB
(Fig. S3†) dH (400 MHz; DMSO; CDHB) 1.35 (18H, bs, 8–16), 1.57
(2H, bs, 17), 1.76 (2H, bs, 7), 5.17 (1H, m, 6), 6.28 (1H, d, J ¼ 2.4
Hz, 2), 6.35 (1H, dd, J ¼ 2.4 Hz; 8.8 Hz, 4), 7.62 (1H, d, J ¼ 8.8 Hz,
5), 10.44 (1H, s, 1), 10.82 (1H, s, 3). dC (DMSO) 20.85 (10), 23.14
(18), 23.36 (11), 23.93 (12), 24.10 (13), 29.09 (14), 39.36 (15),
39.56 (16), 39.77 (17), 39.98 (9), 40.19 (19), 72.73 (8), 102.89 (3),
104.59 (6), 108.71 (1), 131.89 (5), 163.42 (4), 164.70 (2), 169.48 (7)
ppm. ESI-MS (Fig. S4†) m/z 319.22 ([M ꢀ H]ꢀ, 100%). Calculate
for C19H28O4: 320.20. The characterization data were in agree-
ment with that reported by Urraca.24
Analysis of real samples
ZON is oen present in the cereal crops including corn, barley,
sorghum, wheat and oats. Corn, rice and wheat ours were
chosen as samples. Acetonitrile (16 mL) with aqueous NaCl
(4 mL, 40 g Lꢀ1) were added to corn ours (5 g). The mixture was
stirred under vortex conditions for 5 min, ultrasonically
extracted for 15 min and then ltered. The ltrate was rotary
evaporated to near dryness at 60 ꢁC. The residue was dissolved
in acetonitrile for analysis. The recovery study was done by
adding ZON to corn ours, at ZON concentrations 50, 100 and
500 ng gꢀ1. The our–ZON mixture was le to stand for 12 h
before extraction. Rice and wheat ours were treated similarly.
SEM images of MIOM and NIOM are shown in Fig. 1, in
which MIOM particles appeared spherical and of homogeneous
size. NIOM particles' diameters were not as uniform as those of
MIOM, and agglomeration to some extent appeared. The
possible reason is the MAA dimerization and aggregation. In the
MIOM polymerization process, MAA created binding sites
including template sites and background sites. While in the
NIOM polymerization process, the absence of the template
resulted in monomers arranging out of order, and formed
background sites rather than template sites. MAA dimerization
and aggregation could reduce the number of background sites
effectively, but the remaining background sites in NIOM were
more than those in MIOM, which made particles agglomerate
Results and discussion
Synthesis of CDHB and MIOM
ZON is expensive and highly toxic, so CDHB was instead used as through MAA forming hydrogen bonded dimers.10
the template to prepare MIOM. CDHB is similar to ZON in terms The FT-IR spectra of MIOM and NIOM are compared in
of structure, shape, size, functional groups, and hydrophobicity. Fig. 2. Each exhibited the major bands in similar locations,
CDHB has two phenolic hydroxyl groups at the same positions because of their similar compositions. Characteristic peaks
as those in ZON, so it is also able to hydrogen bond with the were observed at 2993 and 2947 cmꢀ1 (saturated C–H),
carboxyl groups of MAA. Hydrophobic CdSe/ZnS QDs modied 1731 cmꢀ1 (C]O), 1473 cmꢀ1 (aromatic C]C), 1398 cmꢀ1
by trioctylphosphine oxide (TOPO) was used, because CDHB is (C–O), and 1161 cmꢀ1 (C–N). The similarity of these spectra
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Fig. 1 SEM image of MIOM (A) and NIOM (B).
Adsorption equilibrium experiments tend to require more
analyte than the adsorption equilibrium experiment and
selective experiments. ZON is expensive and highly toxic, so
CDHB was used in the adsorption equilibrium experiment.
ZON is a trace mycotoxin in food, so low ZON concentration
was used to evaluate the rate of mass transfer and the selec-
tivity of MIOM and NIOM toward ZON. The uorescence
intensity of MIOM decreased with increasing CDHB concen-
tration. Fluorescence quenching was mainly caused by
hydrogen bonding between MIOM specic binding sites and
CDHB. The uorescence quenching of MIOM and NIOM was
quantied by the Stern–Volmer equation:F0/F ¼ 1 + KSV[Q],
where F0 and F are the uorescence intensities of the polymers
in the absence and presence of quencher, respectively. KSV is
the Stern–Volmer constant, and [Q] is the quencher concentra-
tion. The ratio of KSV,MIP to KSV,NIP is dened as the imprinting
factor (IF), and was used to evaluate the polymer selectivity. ZON
was used for adsorption by MIOM and NIOM, to determine their
optimal adsorption times. Fig. 3A shows that the optimal
adsorption times of MIOM and NIOM were both 7.5 h.
Fig. 2 FT-IR spectra of NIOM (a) and MIOM (b).
suggested that the presence of the template during polymeri-
zation and extraction didn't affect the polymer's composition,
as predictable from the nature of the non-covalent imprinting
process.25
Adsorption equilibrium experiments were carried out to
investigate the maximum CDHB adsorption capability of
Adsorption of MIOM
Fig. S5† shows that before CDHB was extracted, the uores- MIOM. Fig. 3B shows that the uorescence intensity of MIOM
cence intensity of MIOM was about 64.1% of that of NIOM. Aer gradually decreased with increasing CDHB concentration.
removing CDHB, the uorescence intensity of MIOM increased, There was no further change in the uorescence intensity of
nearly reaching that of NIOM. The uorescence intensity of MIOM, when the CDHB concentration reached 15.62 mmol Lꢀ1
.
MIOM was quenched upon the addition and rebinding of In contrast, the uorescence intensity of NIOM exhibited no
CDHB.
signicant changes, indicating that the affinity of MIOM was
To compare the effects of different solvents on adsorption, much higher than that of NIOM.
MIOM was dispersed in methanol, ethanol and acetonitrile
The mechanism of uorescence quenching upon MIOM
solutions of CDHB. Fig. S6† shows that aer adsorption, the bonding with ZON was then investigated. MIOM and ZON were
degree of MIOM uorescence quenching in the three solvents is dispersed in acetonitrile, respectively, and both were then
similar. However, the NIOM uorescence intensity exhibit the scanned. Fig. 4 shows that the UV absorption of ZON was close
smallest decrease in acetonitrile, and the difference in uores- to the MIOM band gap. Thus, charge in the MIOM conduction
cence intensity between MIOM and NIOM in acetonitrile was bands could be transferred to the lowest unoccupied molecular
obvious. Thus acetonitrile was more suitable for adsorption and orbital of ZON. Similar charge-transfer mechanisms have been
was used in the following experiments.
reported by Tu et al.26 Charge transfer from MIOM to ZON was
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Fig. 3 (A) Kinetic uptake of ZON onto MIOM (a) and NIOM (b). (B) Adsorption equilibrium of MIOM (a) and NIOM (b) rebinding CDHB.
the proposed mechanism of uorescence quenching. Energy
transfer was excluded, because of the absence of spectral
overlap between ZON absorption and MIOM emission
(562 nm).
Selectivity of MIOM
The mycotoxins ZON, DON, and OTA were used to determinate
the selectivity of MIOM towards ZON. ZON, DON and OTA were
each separately adsorbed by MIOM. Fig. 5A shows that only ZON
resulted in strong uorescence quenching of MIOM, all three
mycotoxins had little effect on the uorescence of NIOM. Thus,
MIOM had a higher adsorption and selectivity for ZON. Fig. 6
shows a comparison of all three tested mycotoxin. While both
DON and OTA posses hydroxyl functionality, it differs from that
of ZON in terms of location and type. The shape and size of DON
and OTA also differ to those of ZON. These factors resulted in
Fig. 4 UV-vis spectra of MIOM dispersed in acetonitrile (a) and ZON
standard solution (b), fluorescence emission spectra of QDs (c).
Fig. 5 (A) Selective adsorption of ZON, DON and OTA by MIOM and NIOM. (B) Test for the interference of different mycotoxins on the fluo-
rescence intensity of MIOM (a), MIOM + interfering mixed mycotoxins (b), MIOM + ZON (c), MIOM + ZON + interfering mixed mycotoxins (d).
(Interfering mixed mycotoxins: OTA and DON).
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Detection range and limit
The detection limit and linear range of the MIOM were inves-
tigated to evaluate its analytical performance. Fig. 7A shows that
the uorescence intensity of MIOM gradually decreases with
increasing ZON concentration. The trend in the MIOM uo-
rescence quenching obeyed the Stern–Volmer equation, and
MIOM exhibited a larger KSV value than NIOM. The IF of MIOM
was 42.17 which indicated its high adsorption ability towards
ZON. MIOM had a linear range of 0.003–3.12 mmol Lꢀ1, with a
correlation of 0.9927 for ZON. The detection limit determined
as the ZON concentration that quenched three times the stan-
dard deviation of a blank signal, divided by the gradient of the
standard curve, and was found to be 0.002 mmol Lꢀ1. The
precision for three replicate detections of a 1.562 mmol Lꢀ1 ZON
solution was 2.2%.
Fig. 6 Structure of CDHB, ZON, DON and OTA.
Application to cereal samples
Recovery experiments were carried out to evaluate the MIOM-
based method, and the results are shown in Table 2. Recoveries
were 94.2–98.7%, 93.1–107.6% and 84.4–106.0% for corn, rice
and wheat our samples, respectively. These values exhibited
the potential of MIOM for detecting ZON in real samples.
poor complementarity of DON and OTA with the MIOM binding
sites. Thus, the selectivity of MIOM towards DON and OTA was
lower than that of ZON.
Competitive adsorption
Analysis of the uorescence of the MIOM in the presence of
mixed mycotoxin solutions was carried out to examine the
adsorption ability of MIOM in complex systems. Fig. 5B
shows that there was no obvious uorescence quenching of
MIOM, upon adsorbing a mixture of OTA and DON. The
uorescence quenching of MIOM was much larger when
adsorbing a mixture of all three mycotoxins or ZON alone.
That suggested that any interference of DON and OTA was
insignicant. In summary, MIOM can be used as a selective
and sensitive recognition material in complex systems. This
is because its imprinted binding cavities bind ZON very
efficiently.
Table 2 Mean ZON recoveries and relative standard deviations (RSD,
%) for cereal samples spiked using various concentration ZON (n ¼ 3)
Spiked amount Detected amount Recovery
Samples
(ng gꢀ1
)
(ng gꢀ1
)
(%)
RSD (%)
Corn our
50
100
500
50
100
500
50
47.1
96.3
493.5
49.2
93.1
538
42.2
92.4
530
94.2
96.3
98.7
98.4
93.1
107.6
84.4
92.4
2.6
4.7
1.2
7.4
4.9
3.0
2.8
3.9
2.1
Rice our
Wheat our
100
500
106.0
Fig. 7 (A) Fluorescence emission spectra of MIOM with increasing ZON concentration. (B) The ZON concentration calibration curve, error bars ¼
ꢃstandard deviation.
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Conclusions
A simple molecularly imprinted optosensing material for
detecting ZON in cereal samples was developed. Incorporating
the template CDHB into the preparation of MIOM reduced the
synthesis cost, and enhances the handling safety. Observing the
quenching of uorescence intensity allowed the determination
of ZON concentration as low as 0.002 mmol Lꢀ1. MIOM exhibi-
ted high selectivity, sensitivity and stability, and could be
applied for the detection of ZON in complex matrices. This
provides opportunities for higher selectivity analysis.
Acknowledgements
This work was supported by the Ministry of Science and Tech-
nology of China (project no. 2012AA101602) and the National
Science Foundation for Distinguished Young Scholars of China
(project no. 31225021) and General Administration of Quality
Supervision, Inspection and Quarantine of the People's
Republic of China (Project no. 201210053) and the Program for
Changjiang Scholars and Innovative Research Team in Univer-
sity (Project no. IRT1166).
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