“Turn off-on” fluorescent sensor based on quantum dots and self-assembled porphyrin for rapid detection of ochratoxin A

Sensors & Actuators: B. Chemical 302 (2020) 127212

Contents lists available at ScienceDirect

Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb

“Turn off-on” fluorescent sensor based on quantum dots and self-assembled porphyrin for rapid detection of ochratoxin A

T

Li Liua, Qingwen Huanga, Zafar Iqbal Tanveera, Keqiu Jianga, Jinghui Zhanga, Hongye Pana, ⁎ ⁎ Lianjun Luana, Xuesong Liua, Zheng Hanb, , Yongjiang Wua, a

College of Pharmaceutical Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China Institute for Agro-food Standards and Testing Technology, Shanghai Key Laboratory of Protected Horticultural Technology, Laboratory of Quality and Safety Risk Assessment for Agro-products (Shanghai), Ministry of Agriculture, Shanghai Academy of Agricultural Sciences, 1000 Jingqi Road, Shanghai, 201403, China

b

ARTICLE INFO

ABSTRACT

Keywords: Quantum dots Self-assembled zinc porphyrin Turn off-on Ochratoxin A

We report herein a “turn off-on” fluorescent sensor based on ZnCdSe quantum dots (ZnCdSe QDs) and selfassembled zinc porphyrin for sensitive and rapid detection of ochratoxin A (OTA). Using environmentally friendly dodecyl dimethyl betaine as “soft template”, zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H-23H-porphine (ZnTPyP) was self-assembled into nanorods (SA-ZnTPyP) through a green process. The OTA detection process involves two steps: (1) the fluorescence of ZnCdSe QDs is significantly quenched by SA-ZnTPyP, and (2) the combination between SA-ZnTPyP and OTA releases ZnCdSe QDs from their quenchers such that the fluorescence is recovered. Under the optimized experimental conditions, the newly developed fluorescent sensor showed a linear response in concentration range 0.5–80 ng mL−1, with a detection limit of 0.33 ng mL−1. The excellent applicability of the system has been verified in milk and coffee samples, with relative recoveries between 98.33% and 103.70%. The proposed fluorescent sensor exhibits excellent selectivity and high sensitivity, and thus could be a promising tool for on-site determination of OTA in food safety control and environmental monitoring.

1. Introduction Ochratoxins are toxic compounds produced as secondary metabolites by Aspergillus ochraceus and Penicillium verrucosum [1,2]. Ochratoxin A (OTA), the most important ochratoxin, showing strong nephrotoxicity, hepatotoxicity, immunotoxicity, teratogenicity and mutagenicity, has been categorized as a potential carcinogen to humans (Group 2B) by the International Agency for Research on Cancer (IARC) [3]. OTA occurs in a variety of foodstuffs, including milk, coffee, peanuts, maize, wines, and ultimately finds its way to the human body through the food chain [4]. Considering its potential threat in terms of food safety and health, maximum residue levels (MRLs) for OTA have been set by the European Commission, which range from 0.5 to 10 ng g−1 in various food commodities [5]. In view of the high toxicity and widespread occurrence of OTA, various analytical methods based on instrumental analysis have been established for its determination, including immunoassay [6], highperformance liquid chromatography (HPLC) [7] and HPLC tandem mass spectrometry (HPLC-MS/MS) [8]. Though the accuracy of these approaches has been well proved, some inevitable shortcomings, such as their time-consuming nature and high cost, over-reliance on ⁎

qualified technical staff and unsuitability for on-site detection, still limit their application [9]. Recently, optical sensing platforms have attracted intense interests by virtue of their easy and rapid monitoring of fluorescence changes induced by the interactions between nanostructured materials and analytes [10]. Highly luminescent semiconductor quantum dots (QDs) are considered to be the most promising fluorescent nanoprobes in optical methods owing to their excellent photostability, large extinction coefficients, chemical stability and biocompatibility [11]. Two different modes, namely “turn off” mode and “turn off-on” modes, have been proposed for the optical sensors based on QDs. Compared to the traditional “turn off” mode, the latter approach based on “turn off-on” fluorescence change (quenching recovery) can not only expand the detection range, but also increase its stability and reduce environmental interferences [12]. Consequently, it has been widely used in the detection of DNA [13], RNA [14], amino acids [15], tumors [16], and anticancer drugs [17]. Since the concentrations of OTA in foodstuffs are commonly at quiet low levels, template materials, which serve to enlarge surface area and improve optical characteristics, are essential for the construction of sensitive and selective optical sensors. Porphyrins and their derivatives

Corresponding authors. E-mail addresses: [email protected] (Z. Han), [email protected] (Y. Wu).

https://doi.org/10.1016/j.snb.2019.127212 Received 18 June 2019; Received in revised form 18 September 2019; Accepted 28 September 2019 Available online 30 September 2019 0925-4005/ © 2019 Elsevier B.V. All rights reserved.

Sensors & Actuators: B. Chemical 302 (2020) 127212

L. Liu, et al.

have been widely employed in the catalysis [18], photovoltaic devices [19], and chemical sensors [20] due to their remarkable optical, electronic, thermal, and mechanical properties. Recently, the designability of assembled porphyrin nanomaterial has led to nanoporphyrins as promising advanced nanomaterials because of their excellent photoelectric, physical, and surface properties, macroscopic quantum tunneling, and quantum size effects [21,22]. These peculiar properties endow assembled porphyrins with optimal sensitivity to local environmental changes and interaction with various potential analytes, allowing their application in the field of supramolecular chemistry, light harvesting, photosensitization, photonics, and various sensor technologies [23,24]. Zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H,23Hporphine (ZnTPyP) is one of the most widely studied porphyrin-based systems by virtue of its improved stability, and the ability to self-assemble into more favorable arrangements through coordination of its peripheral pyridine groups to its core metal ions [25]. However, the conventional preparation of self-assembled ZnTPyP requires cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) as a surfactant [26], which are toxic to animals and the environment [27,28]. Here, an innovative “turn off-on” fluorescent sensor utilizing ZnCdSe QDs and self-assembled zinc porphyrin for the rapid detection of OTA has been constructed for the first time. The self-assembled ZnTPyP (SA-ZnTPyP) was prepared by an environmentally friendly approach by using dodecyl dimethyl betaine, and exhibited remarkably spectral properties. A “turn off-on” mode has been established, whereby the intensity of fluorescence signal is proportional to the amounts of OTA (Scheme 1). Our fluorescent sensor exhibits excellent analytical performances (high accuracy, stability and selectivity), and is thus expected to provide a novel tool for the rapid and sensitive detection of OTA. The described strategy might also be extended to other mycotoxins.

OTA, zearalenone (ZEA), HT-2 toxin (HT-2), T-2 toxin (T-2), and deoxynivalenol (DON) were purchased from Romer Labs Inc. (St. Louis, MO, USA) and dissolved in acetonitrile to prepare 10 μg mL−1 of stock solutions. The stock solutions were stored at −20 °C in the dark. Milk and coffee were randomly collected from supermarkets in Hangzhou and stored at 4 °C in the dark. 2.2. Apparatus Fluorescence spectra were acquired by an F-2700 fluorescence spectrophotometer (Hitachi High-Technologies Co., Japan). The experimental parameters were set as follows: excitation wavelength (λex), 360 nm; excitation slit, 10 nm; emission slit, 10 nm. The synthesized nanomaterials were characterized by a JEM-1010 transmission electron microscope (TEM; JEOL Ltd., Japan) and an SU8010 scanning electron microscope (SEM, Hitachi High-Technologies Co., Japan). The UV/Vis measurements were performed using a JASCO BV-550 UV/Vis spectrophotometer (Japan split light Co., Japan). UHPLC was performed via a Waters Acquity UHPLC system (Waters, Milford, MA, USA). The separated mycotoxins were analyzed by a Triple-Quad™ 5500 mass spectrometer (AB Sciex, Foster City, CA, USA) with an electrospray ionization source operated in positive (ESI+) modes. Deionized water used throughout the study was prepared by a Milli-Q Reference water purification system (Merck Millipore, USA). 2.3. Synthesis of NAC-capped ZnCdSe QDs Water-soluble NAC-capped ZnCdSe QDs were synthesized by a hydrothermal route. NaBH4 was combined with Se in water (3.0 mL) to produce sodium hydroselenide (NaHSe, 0.0844 mol L−1). NAC (0.126 g) and ZnCl2 (0.037 g) were added to water (40 mL) and the mixture was magnetically stirred for 20 min. The mixture was adjusted to pH 9.7 with aqueous NaOH (1 mol L−1). CdCl2 (0.58 mg) was then added, and stirring was continued for 10 min under a nitrogen atmosphere with the flask immersed in an ice bath. Finally, an aliquot (700 μL) of the aforementioned NaHSe solution was added and the mixture was further stirred for 10 min, transferred to a 50 mL Teflonlined stainless-steel autoclave, and heated at 200 °C for 1 h.

2. Experimental 2.1. Experimental materials and reagents Se, NaBH4 and CdCl2 were purchased from Aladdin Chemistry Co. Ltd (Shanghai, China). KCl, Na2CO3, MgCl2, CaCl2, DMF, and acetonitrile were purchased from Tianjin Yongda Chemical Reagent Co. Ltd (Tianjin, China). N-acetyl-L-cysteine (NAC) was purchased from Yuanye Biological Technology Co. Ltd (Shanghai, China). Dodecyl dimethyl betaine was purchased from Shandong Yousuo Chemical Technology Co. Ltd (Shandong, China). ZnCl2 was purchased from Xilong Science Co. Ltd (Guangdong, China). TPyP was purchased from J&K Scientific Ltd (Shanghai, China).

2.4. Preparation of SA-ZnTPyP ZnTPyP was prepared by the metallization of TPyP [15]. Solid ZnTPyP (0.49 mg) was dispersed in DMF (10 mL) with sonication for 15 min to prepare a ZnTPyP/DMF stock solution. Dodecyl dimethyl betaine (3.5 mL) was diluted in water (42 mL), and an aliquot (2 mL) of the aforementioned stock solution was injected under continuous

Scheme 1. (A) Synthesis of SA-ZnTPyP. (B) The “turn off-on” mechanism of ZnCdSe QDs/SA-ZnTPyP for OTA detection. 2

Sensors & Actuators: B. Chemical 302 (2020) 127212

L. Liu, et al.

stirring. After stirring for 10 min, the mixture became greenish, transparent, and colloid-like due to the self-assembly of supramolecular SAZnTPyP.

the Soret peak (B band), and a weak peak at 557 nm (Q band). In the spectrum of SA-ZnTPyP (b), the B band was split from the unimodal absorption at 424 nm to two disparate absorption peaks at 425 nm and 470 nm. The intensity of Q-band was significantly enhanced compared to that of the monomeric species and showed a noticeable red shift, indicative of J-aggregation. Moreover, the UV/Vis spectrum of SAZnTPyP covered a broader visible area, greatly improved the utilization of visible light.

2.5. OTA analysis Fluorescence quenching of ZnCdSe QDs/SA-ZnTPyP was performed by mixing SA-ZnTPyP solution (250 μL) with ZnCdSe QDs solution (70 μL), making the mixture up to 1 mL in Tris-HCl (pH 8.0, 50 mmol L−1), and leaving it at room temperature for 5 min. The concentrations of ZnCdSe QDs and SA-ZnTPyP were set at 1.47 × 10−8 mol L−1 and 3.96 × 10−7 mol L−1, respectively. The fluorescence recovery experiment was then conducted by adding an aliquot (100 μL) of OTA solution to the above quenched solution. After setting aside for 5 min at room temperature, the OTA concentration was measured in triplicate by means of a fluorescence spectrophotometer.

3.3. Fluorescence quenching process Fluorescence measurements were then performed on water-soluble NAC-capped ZnCdSe QDs, whereupon a sharp and strong emission peak was observed at 515 nm (Fig. 2A). The fluorescence intensity of SAZnTPyP (3.96 × 10−7 mol·L−1) was quite low (Fig. S1), which could not affect the fluorescence intensity of ZnCdSe QDs. Since the photoluminescence of ZnCdSe QDs is known to be pH-dependent, Tris-HCl buffer (50 mmol L-1, pH = 8.0) was used to disperse the QDs. As displayed in Fig. 2A, the fluorescence emission intensity of ZnCdSe QDs gradually decreased with increasing SA-ZnTPyP concentration in the range of 0.079-0.475 μmol L−1. In order to evaluate the sensitivity of the “turn off” fluorescent probe of ZnCdSe QDs/SA-ZnTPyP, its quenching efficiency was quantified using the Stern-Volmer (SV) equation [21]:

2.6. Application Different amounts of OTA standard solution were separately spiked into samples of milk (1.5 mL) or coffee (0.5 g), and then dispersed with acetonitrile to make a total volume of 5 mL, thereby producing a series of spiked solutions (OTA concentrations: 2, 6, 30, and 60 ng mL−1). The samples were ultrasonicated for 10 min and centrifuged at 4000 rpm for 10 min. And the subsequent manipulation was conducted according to the reported strategy.

F0/F1=KSV[M]+1 Here, F0 and F1 are the fluorescence intensities of the ZnCdSe QDs in the absence and presence of SA-ZnTPyP, respectively; [M] is the concentration of SA-ZnTPyP, and the quenching constant Ksv is defined as the quenching efficiency of SA-ZnTPyP. The equation reveals that the increasing of F0/F1 is directly proportional to the enhancement of SAZnTPyP concentration. As shown in Fig. 2B, the Ksv of SA-ZnTPyP to the fluorescence of ZnCdSe QDs is 3.2 × 106 L mol−1, and the Stern − Volmer plot showed a good linear correlation (R2 = 0.9975) in the SA-ZnTPyP concentration range 0.079-0.475 μmol L-1, implying that SA-ZnTPyP exhibited good quenching ability towards the fluorescence intensity of ZnCdSe QDs. The stability of ZnCdSe QDs and quenching process were investigated. The fluorescence intensities of ZnCdSe QDs and ZnCdSe QDs/SA-ZnTPyP system kept consistent when they were stored at 4 ℃ for 0, 1, 2 and 3 months, indicating a satisfactory longterm stability of ZnCdSe QDs and ZnCdSe QDs/SA-ZnTPyP (Fig. S2, Fig S3).

3. Results and discussion 3.1. Design strategy for OTA detection The preparation of self-assembled nanocrystalline SA-ZnTPyP is shown in Scheme. 1A. Through the strong π-π stacking interactions of the porphine rings and hydrophobic effects, the porphyrin molecules spontaneously formed J-aggregates in the micellar structure of dodecyl dimethyl betaine, thereby adopting an ordered stable nanorod structure [26]. The mechanism of the established “turn off-on” model is shown in Scheme. 1B. SA-ZnTPyP was first encapsulated by dodecyl dimethyl betaine, resulting in a zwitterionic form in alkaline aqueous media [29], which could bind with negatively charged ZnCdSe QDs and accept their electrons. Through the photo-induced electron transfer (PET), the SA-ZnTPyP could efficiently quench the fluorescence of ZnCdSe QDs [30], providing an ideal “off” state for the detection. OTA is a weakly acidic substance, and can be negatively charged in a weakly alkaline solution. It can combine with SA-ZnTPyP, shortening the distance between them. Nitrogen/zinc coordination also contributes to the conjunction of SA-ZnTPyP and OTA molecules [31]. The synergistic effects are sufficiently strong to destroy the relatively weak interaction between SA-ZnTPyP and ZnCdSe QDs. As a result, the fluorescence is recovered, providing an ideal “on” state.

3.4. Optimization of the concentration ratio of SA-ZnTPyP Although a higher concentration of SA-ZnTPyP could quench the fluorescence of ZnCdSe QDs to a large extent, or even completely, excessive quencher will limit the recovery of this fluorescence after the addition of OTA. This may be ascribed to the combination between OTA and “free” SA-ZnTPyP. Conversely, insufficient SA-ZnTPyP could not effectively quench the fluorescence of ZnCdSe QDs, which may influence the detection of OTA. Therefore, the amount of SA-ZnTPyP added in the experiment was investigated to ensure the sensitivity of the ZnCdSe QDs/SA-ZnTPyP probe. The value I is employed to describe relative fluorescence recovery rate:

3.2. Characterization of SA-ZnTPyP TEM and SEM were employed to identify the morphological characteristics of SA-ZnTPyP. As illustrated in Fig. 1A, B, the obtained SAZnTPyP nanoparticles were relatively uniformly distributed and had a well-defined rod structure of length around 280 nm. These results clearly indicated that the porphyrins were successfully stacked into nanoporphyrins by the surfactants. The interaction of ZnCdSe QDs and SA-ZnTPyP was investigated by TEM. As shown in Fig. 1C, the ZnCdSe QDs were clearly homogeneously distributed on the surface of SAZnTPyP. UV/Vis adsorption spectrometry was further used to characterize of the ZnTPyP monomer and SA-ZnTPyP (Fig. 1D). ZnTPyP monomer (a) exhibited a strong characteristic absorption peak at 424 nm, known as

I=(F2-F1)/F0 F0 represents the fluorescence intensity of ZnCdSe QDs. F1 represents the fluorescence intensity of ZnCdSe QDs/SA-ZnTPyP. F2 is the fluorescence intensity in the presence of OTA in ZnCdSe QDs/SAZnTPyP system. As shown in Fig. 3, excessive or insufficient SA-ZnTPyP is not beneficial to the fluorescence recovery of ZnCdSe QDs. When the concentration of SA-ZnTPyP was 0.396 μmol L−1, the value I reached the maximum (0.2424). The fluorescence of ZnCdSe QDs was quenched 3

Sensors & Actuators: B. Chemical 302 (2020) 127212

L. Liu, et al.

Fig. 1. (A) TEM images of SA-ZnTPyP. Inset: magnified TEM image of SA-ZnTPyP. (B) SEM image of SA-ZnTPyP. (C) TEM image of ZnCdSe QDs. Inset: TEM image of ZnCdSe QDs/SA-ZnTPyP. (D) UV/Vis spectra of (a) ZnTPyP and (b) SA-ZnTPyP.

Fig. 2. (A) Fluorescence quenching behaviors of ZnCdSe QDs (1.47 × 10−8 mol L−1) after the addition of 0, 0.079, 0.158, 0.237, 0.317, 0.396 and 0.475 μmol L−1 of SA-ZnTPyP (a to g). (B) Linear plot of relative fluorescence intensity (F0/F1) as a function of SA-ZnTPyP (0.079–0.475 μmol L−1) (n = 3).

to 44.9% and recovered to 67.9% of the original fluorescence after exposing to OTA (60 ng mL-1). Therefore, the concentration of SAZnTPyP was fixed as 0.396 μmol L−1.

ZnCdSe QDs were investigated in the absence of SA-ZnTPyP. After exposing to OTA at various concentrations, the fluorescence spectra of ZnCdSe QDs were largely overlapped and indistinguishable (Fig. 4A), indicating that a change in OTA concentration has no effect on the fluorescence intensity of ZnCdSe QDs in the absence of SA-ZnTPyP. On the contrary, significant fluorescence signal changes were observed when OTA was added to ZnCdSe QDs/SA-ZnTPyP system (Fig. 4B). The interaction between SA-ZnTPyP and OTA was confirmed by a

3.5. Sensitivity of OTA detection In order to confirm that the fluorescence recovery was induced by the interaction of SA-ZnTPyP with OTA, fluorescence changes of 4

Sensors & Actuators: B. Chemical 302 (2020) 127212

L. Liu, et al.

Fig. 3. (A) Fluorescence intensity histogram of F1 and F2. (SA-ZnTPyP: 0.079, 0.158, 0.237, 0.317, 0.396, 0.475 and 0.553 μmol L−1; ZnCdSe QDs: 1.47 × 10-8 mol L−1; OTA: 60 ng mL−1). (B) The plot of I vs the concentration of SA-ZnTPyP (I=(F2-F1)/F0).

Fig. 4. (A) The fluorescence spectra of NAC-capped ZnCdSe QDs (1.47 × 10−8 mol L−1) after the addition of OTA (0.5, 2, 6, 10, 30, 40, 60 and 80 ng mL−1). (B) Fluorescence spectra of the ZnCdSe QDs/SA-ZnTPyP (ZnCdSe QDs: 1.47 × 10−8 mol L−1; SA-ZnTPyP: 0.396 μmol L−1) with the addition of OTA (0.5, 2, 6, 10, 30, 40, 60 and 80 ng mL-1). (C) UV/Vis spectra of (a) SA-ZnTPyP and (b) SA- ZnTPyP/OTA. (D) Linear plot of fluorescence intensity F2/F0 at 515 nm as a function of OTA concentration (0.5, 2, 6, 10, 30, 40, 60 and 80 ng mL-1) (n = 3).

significantly reduced UV absorption of the former after exposure to the latter (Fig. 4C). The above observations indicated that there is no interaction between ZnCdSe QDs and OTA, and that OTA can competitively bind to SA-ZnTPyP to restore the fluorescence of ZnCdSe QDs in a ZnCdSe QDs/SA-ZnTPyP system. Under the optimal conditions, the fluorescence signal enhanced with increasing concentration of OTA, and a good linear relationship with a correlation coefficient (R2) of 0.9958 was observed over the concentration range 0.5–80 ng mL−1 (Fig. 4D). The regression equation was F2/F0 = 2.30449COTA+0.53409 (COTA: μg mL−1). The limit of detection (LOD) for OTA was calculated as three times the standard deviation of background, that is, 0.33 ng mL−1. The stability of present

sensor was evaluated by measuring the fluorescence intensity of three different samples with the same concentration of OTA (OTA: 60 ng mL−1) in different days for three times. The relative standard deviation (RSD) was 2.57%, thereby confirming good stability of sensing platform. The detection of OTA was not reversible, which only can perform one measurement. 3.6. Selectivity of OTA detection The selectivity of the established sensing platform was evaluated by determining OTA in the presence other interfering substances, including foreign ions (1 × 10−5 mol L-1 of Mg2+, Zn2+, Na+, Ca2+, and 5

Sensors & Actuators: B. Chemical 302 (2020) 127212

L. Liu, et al.

Fig. 5. (A) Selectivity of the established sensor towards naturally abundant foreign ions (K+, Mg2+, Na+, Zn2+, and Ca2+, 1 × 10−5 mol L−1; OTA: 40 ng mL−1) (B) Selectivity of the established sensor towards frequently co-occurring mycotoxins. The concentrations were 60 ng mL−1 for OTA and 80 ng mL−1 for the other mycotoxins.

K+) and several frequently co-occurring mycotoxins (80 ng mL-1 of ZEA, DON, T-2, and HT-2). The responses did not change significantly with the addition of different foreign ions (Fig. 5A), indicating that these commonly existing substances have no significant effect towards ZnCdSe QDs/SA-ZnTPyP/OTA, and that the established probe has excellent stability for the detection of OTA. And as shown in Fig. 5B, the F2/F0 was obviously increased after the addition of OTA, but no significant change was observed with ZEA, DON, T-2, or HT-2. Considering that a sample may contain multiple mycotoxins, we also investigated the recognition performance to OTA in the presence of a variety of interfering substances. Even five mycotoxins (OTA, T-2, HT2, ZEA and DON) were mixed together, these interfering substances still could not influence the detection of OTA. Those results indicated that the present sensor showed satisfactory selectivity for OTA detection. This could be attributed to the high specific binding between OTA and SA-ZnTPyP, and the affinity of nitrogen/zinc coordination and electrostatic interaction, leading to the release of the ZnCdSe QDs and allowing the detection of OTA in complex matrices without separations. To further characterize the fluorescent sensing platform, it was compared with the previously reported methods for the rapid determination detection of OTA. As shown in Table 1, the sensitivity, linear range, and detection time were comparable to those of the previously established sensors, and the total detection time with our sensor was only 5 min, distinctly shorter than those of the others, verifying the excellent analytical performance of the proposed fluorescent sensor at detecting OTA in terms of high sensitivity and selectivity, wide linear dynamic range, and satisfactory detection limit. Compared with other fluorescence “turn off-on” methods, the performance of the constructed method is comparable or even better (Table S2).

Table 2 OTA recoveries in milk and coffee samples (n = 3). Samples

Spiked (ng mL−1)

Detected (ng mL−1)

Recovery (%)

RSD (%)

Milk

2.00 6.00 30.00 60.00 2.00 6.00 30.00 60.00

2.06 ± 0.055 5.92 ± 0.10 31.11 ± 1.01 58.99 ± 1.49 2.05 ± 0.057 6.13 ± 0.31 29.61 ± 0.42 59.81 ± 1.29

102.79 ± 2.76 98.62 ± 1.70 103.70 ± 3.39 98.33 ± 2.49 102.63 ± 2.83 102.11 ± 5.09 98.71 ± 1.41 99.69 ± 2.16

2.68 1.72 3.27 2.53 2.76 4.99 1.44 2.17

Coffee

3.7. Analysis of naturally contaminated milk and coffee samples In order to verify the feasibility and reliability of the proposed fluorescent ZnCdSe QDs/SA-ZnTPyP sensor for practical applications, it was deployed for analyzing milk and coffee samples. As shown in Table 2, the recoveries and RSD of the spiked samples were in the ranges 98.33%–103.70% and 1.72%–2.68% in milk, and 98.71%–102.63% and 1.44%–4.99% in coffee, respectively. The results obtained were further verified by an in-parallel LC − MS/MS [40]. Similar results were obtained for UHPLC − MS/MS and the current method (Table S1), demonstrating the excellent detection capability of the constructed sensor. These satisfactory results demonstrated that the proposed method can be used for the sensitive surveillance of OTA in complicated matrixes. 4. Conclusions A rapid and sensitive “turn off-on” fluorescent sensor based on

Table 1 Comparison of the performances of different sensors for the determination of OTA. Detection method

Matrix

Linear range (ng mL−1)

LOD (ng mL−1)

Detection Time (min)

Reference

Electrochemical aptasensor Colorimetric aptasensor Fluorescent aptasensor Surface-enhanced raman scattering aptasensor Fluorescent aptasensor Fluorescent aptasensor Fluorescent aptasensor Fluorescent aptasensor Optical sensor Fluorescent sensor

Red wine Corn Red wine Grape juice Red wine Red wine and beer Red wine Red wine / Coffee and milk

0.01-10 0.05-2.0 1-1000 0.01-50 8-202 8.08-202 0-1 2.02-40.38 0.5-10 0.5-80

0.003 0.023 1 0.004 6.95 6.66 0.013 1.95 / 0.33

80 20 40 240 15 45 120 110 20 5

[2] [32] [33] [34] [35] [36] [37] [38] [39] This work

6

Sensors & Actuators: B. Chemical 302 (2020) 127212

L. Liu, et al.

ZnCdSe QDs and self-assembled porphyrin has been developed for the detection of OTA for the first time. SA-ZnTPyP was successfully synthesized through an environmentally friendly approach, and exhibited remarkably spectral properties. A fluorescent “turn off-on” mode has been established for the detection of OTA, resulting in excellent performance of the proposed optical sensing platform, including wide linear range, satisfactory recovery, optimal stability, high selectivity and sensitivity. Significantly, this approach may provide a new strategy for on-site monitoring of OTA and allow extension of the application of such optical methods to the analysis of different kinds of compounds in food samples.

[13]

[14]

[15]

Declaration of Competing Interest

[16]

None. [17]

Acknowledgments This work was supported by the National Major Scientific and Technological Special Project for “Significant New Drugs Development” [No. 2018ZX09201010], the National Key R&D Plan [No. 2017YFC1700806], the National Natural Science Foundation of China [No. 31671950], and the Shanghai City Sci-Tech Joint Research Project in Yangtze River Delta of Shanghai Municipal Science and Technology Commission [No. 18395810100].

[18]

Appendix A. Supplementary data

[21]

Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.snb.2019.127212.

[22]

References

[23]

[19]

[20]

[1] H.B. Bostan, N.M. Danesh, G. Karimi, M. Ramezani, S.A. Mousavi Shaegh, K. Youssefi, F. Charbgoo, K. Abnous, S.M. Taghdisi, Ultrasensitive detection of ochratoxin A using aptasensors, Biosens. Bioelectron. 98 (2017) 168–179, https:// doi.org/10.1016/j.bios.2017.06.055. [2] Y. Wang, G. Ning, Y. Wu, S. Wu, B. Zeng, G. Liu, X. He, K. Wang, Facile combination of beta-cyclodextrin host-guest recognition with exonuclease-assistant signal amplification for sensitive electrochemical assay of ochratoxin A, Biosens. Bioelectron. 124–125 (2019) 82–88, https://doi.org/10.1016/j.bios.2018.10.007. [3] C. Jiang, L. Lan, Y. Yao, F. Zhao, J. Ping, Recent progress in application of nanomaterial-enabled biosensors for ochratoxin A detection, TrAC Trend. Anal. Chem. 102 (2018) 236–249, https://doi.org/10.1016/j.trac.2018.02.007. [4] M.E. Flores-Flores, E. Lizarraga, A.Ld. Cerain, E. Gonzalez-Penas, Presence of mycotoxins in animal milk: a review, Food Control 53 (2015) 163–176, https://doi. org/10.1016/j.foodcont.2015.01.020. [5] M. Xiao, X. Bai, Y. Liu, L. Yang, X. Liao, Simultaneous determination of trace Aflatoxin B1 and Ochratoxin A by aptamer-based microchip capillary electrophoresis in food samples, J. Chromatogr. A 1569 (2018) 222–228, https://doi.org/10. 1016/j.chroma.2018.07.051. [6] X. Zou, C. Chen, X. Huang, X. Chen, L. Wang, Y. Xiong, Phage-free peptide ELISA for ochratoxin A detection based on biotinylated mimotope as a competing antigen, Talanta 146 (2016) 394–400, https://doi.org/10.1016/j.talanta.2015.08.049. [7] C.L. Luan, L. Wang, F.F. Chen, S. Wang, L. Zhao, L.H. Shao, Determination of ochratoxin A in pig muscle using dispersive liquid-liquid microextraction combined with high-performance liquid chromatography, Food Anal. Method 9 (2016) 1490–1494, https://doi.org/10.1007/s12161-015-0330-4. [8] M.A. Andrade, F.M. Lancas, Determination of ochratoxin A in wine by packed intube solid phase microextraction followed by high performance liquid chromatography coupled to tandem mass spectrometry, J. Chromatogr. 1493 (2017) 41–48, https://doi.org/10.1016/j.chroma.2017.02.053. [9] I.Y. Goryacheva, S.D. Saeger, M. Lobeau, S.A. Eremin, I. Barna-Vetró, C.V. Peteghem, Approach for ochratoxin A fast screening in spices using clean-up tandem immunoassay columns with confirmation by high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS), Anal. Chim. Acta 577 (2006) 38–45, https://doi.org/10.1016/j.aca.2006.06.033. [10] Z. Hu, W.P. Lustig, J. Zhang, C. Zheng, H. Wang, S.J. Teat, Q. Gong, N.D. Rudd, J. Li, Effective detection of mycotoxins by a highly luminescent metal−organic framework, J. Am. Chem. Soc. 137 (2015) 16209–16215, https://doi.org/10.1021/ jacs.5b10308. [11] S. Saha, G. Das, J. Thote, R. Banerjee, Photocatalytic metal-organic framework from CdS quantum dot incubated luminescent metallohydrogel, J. Am. Chem. Soc. 136 (2014) 14845–14851, https://doi.org/10.1021/ja509019k. [12] M. Li, Y. Zheng, W. Liang, Y. Yuan, Y. Chai, R. Yuan, An ultrasensitive “on–off–on”

[24]

[25] [26] [27]

[28]

[29]

[30]

[31]

[32]

[33] [34]

7

photoelectrochemical aptasensor based on signal amplification of a fullerene/CdTe quantum dots sensitized structure and efficient quenching by manganese porphyrin, Chem. Commun. 52 (2016) 8138–8141, https://doi.org/10.1039/C6CC02791A. Y. Fan, M. Yu, Y. Xu, Q. Wang, Y. Hu, H. Fu, Y. She, Nanoporphyrin/CdTe quantum dots: a robust tool for effective differentiation among DNA structures, Sens. Actuator. B: Chem. 281 (2019) 623–633, https://doi.org/10.1016/j.snb.2018.10. 160. Y. Cao, H. Dong, Z. Yang, X. Zhong, Y. Chen, W. Dai, X. Zhang, Aptamer-conjugated graphene quantum dots/porphyrin derivative theranostic agent for intracellular cancer-related microRNA detection and fluorescence-guided photothermal/photodynamic synergetic therapy, ACS Appl. Mater. Int. 9 (2017) 159–166, https://doi. org/10.1021/acsami.6b13150. H. Fu, O. Hu, Y. Fan, Y. Hu, J. Huang, Z. Wang, Y. She, Rational design of an “onoff-on” fluorescent assay for chiral amino acids based on quantum dots and nanoporphyrin, Sens. Actuator. B: Chem. 287 (2019) 1–8, https://doi.org/10.1016/j. snb.2019.02.023. C.M. Lemon, E. Karnas, Han X, O.T. Bruns, T.J. Kempa, D. Fukumura, M.G. Bawendi, Ra.K. Jain, D.G. Duda, D.G. Nocera, Micelle-encapsulated quantum dot-porphyrin assemblies as in vivo two-photon oxygen sensors, J. Am. Chem. Soc. 137 (2015) 9832–9842, https://doi.org/10.1021/jacs.5b04765. E. Vaishnavi, R. Renganathan, “Turn-on-off-on” fluorescence switching of quantum dots-cationic porphyrin nanohybrid: a sensor for DNA, Analyst 139 (2014) 225–234, https://doi.org/10.1039/C3AN01871G. S. Lin, C.S. Diercks, Y.B. Zhang, N. Kornienko, E.M. Nichols, Y. Zhao, A.R. Paris, D. Kim, P. Yang, O.M. Yaghi, C.J. Chang, Covalent organic frameworks comprising cobalt porphyrins for catalytic CO2 reduction in water, Science 349 (2015) 1208–1213, https://doi.org/10.1126/science.aac8343. S. Chen, L. Xiao, X. Zhu, X. Peng, W.K. Wong, W.Y. Wong, Solution-processed new porphyrin-based small molecules as electron donors for highly efficient organic photovoltaics, Chem. Commun. 51 (2015) 14439–14442, https://doi.org/10.1039/ C5CC05807D. R. Paolesse, S. Nardis, D. Monti, M. Stefanelli, C.D. Natale, Porphyrinoids for chemical sensor applications, Chem. Rev. 117 (2017) 2517–2583, https://doi.org/10. 1021/acs.chemrev.6b00361. Y. Qiu, P. Chen, M. Liu, Evolution of various porphyrin nanostructures via an oil/ aqueous medium: controlled self-assembly, further organization, and supramolecular chirality, J. Am. Chem. Soc. 132 (2010) 9644–9652, https://doi.org/10.1021/ ja1001967. D. Wang, L. Niu, Z.Y. Qiao, D.B. Cheng, J. Wang, Y. Zhong, F. Bai, H. Wang, H. Fan, Synthesis of self-assembled porphyrin nanoparticle photosensitizers, ACS Nano 12 (2018) 3796–3803, https://doi.org/10.1021/acsnano.8b01010. W. Cai, G. Zhang, K. Lu, H. Zeng, S. Cosnier, X. Zhang, D. Shan, Enhanced electrochemiluminescence of one-dimensional self-assembled porphyrin hexagonal nanoprisms, ACS Appl. Mater. Int. 9 (2017) 20904–20912, https://doi.org/10. 1021/acsami.7b05188. S. Ishihara, J. Labuta, W.V. Rossom, D. Ishikawa, K. Minami, J.P. Hill, K. Ariga, Porphyrin-based sensor nanoarchitectonics in diverse physical detection modes, Phys. Chem. Chem. Phys. 16 (2014) 9713–9746, https://doi.org/10.1039/ C3CP55431G. F. Bai, Z. Sun, H. Wu, R.E. Haddad, E.N. Coker, J. Yu Huang, M.A. Rodriguez, H. Fan, Porous one-dimensional nanostructures through confined cooperative selfassembly, Nano Lett. 11 (2011) 5196–5200, https://doi.org/10.1021/nl203598n. C. Zhang, P. Chen, H. Dong, Y. Zhen, M. Liu, W. Hu, Porphyrin supramolecular 1D structures via surfactant assisted self-assembly, Adv. Mater. 27 (2015) 5379–5387, https://doi.org/10.1002/adma.201501273. Q. Huang, Y. Zou, S. Zhong, X. Yang, J. Li, W. Huang, H. Zhu, C. Cheng, M. Ding, L. Zhu, Q. Shi, Silica-coated gold nanorods with high photothermal efficiency and biocompatibility as a contrast agent for in vitro terahertz imaging, J. Biomed. Nanotechnol. 15 (11) (2019) 910–920, https://doi.org/10.1166/jbn.2019.2738. J. Wang, J. Wang, C. Xu, R. Liu, Y. Chen, Molecular mechanism of catalase activity change under sodium dodecyl sulfate-induced oxidative stress in the mouse primary hepatocytes, J. Hazard. Mater. 307 (2016) 173–183, https://doi.org/10.1016/j. jhazmat.2015.11.060. Q. Lin, K. Liu, Z. Cui, X. Pei, J. Jiang, B. Song, pH-responsive pickering foams stabilized by silica nanoparticles in combination with trace amount of dodecyl dimethyl carboxyl betaine, Colloid. Surf. A 544 (2018) 44–52, https://doi.org/10. 1016/j.colsurfa.2018.02.027. K. Zhu, X. Hu, Q. Ge, Q. Sun, Fluorescent recognition of deoxyribonucleic acids by a quantum dot/meso-tetrakis (N-methylpyridinium-4-yl) porphyrin complex based on a photo induced electron-transfer mechanism, Anal. Chim. Acta 812 (2014) 199–205, https://doi.org/10.1016/j.aca.2014.01.007. X. Huang, B.H. Rickman, B. Borhan, N. Berova, K. Nakanishi, Zinc porphyrin tweezer in host-guest complexation: determination of absolute configurations of diamines, amino acids, and amino alcohols by circular dichroism, J. Am. Chem. Soc. 120 (1998) 6185–6186, https://doi.org/10.1021/ja973539e. C. Lin, H. Zheng, M. Sun, Y. Guo, F. Luo, L. Guo, B. Qiu, Z. Lin, G. Chen, Highly sensitive colorimetric aptasensor for ochratoxin A detection based on enzyme-encapsulated liposome, Anal. Chim. Acta 1002 (2018) 90–96, https://doi.org/10. 1016/j.aca.2017.11.061. Z. Lu, X. Chen, W. Hu, A fluorescence aptasensor based on semiconductor quantum dots and MoS2 nanosheets for ochratoxin A detection, Sens. Actuator B: Chem. 246 (2017) 61–67, https://doi.org/10.1016/j.snb.2017.02.062. B. Sha, X. Ma, S. Zhao, Y. Lv, X. Hun, H. Wang, Z. Wang, Nanogapped Au(core) @ Au-Ag(shell) structures coupled with Fe3O4 magnetic nanoparticles for the detection of ochratoxin A, Anal. Chim. Acta 1033 (2018) 165–172, https://doi.org/10. 1016/j.aca.2018.05.058.

Sensors & Actuators: B. Chemical 302 (2020) 127212

L. Liu, et al. [35] L. Lv, C. Cui, C. Liang, W. Quan, S. Wang, Z. Guo, Aptamer-based single-walled carbon nanohorn sensors for ochratoxin A detection, Food Control 60 (2016) 296–301, https://doi.org/10.1016/j.foodcont.2015.08.002. [36] L. Lv, D. Li, R. Liu, C. Cui, Z. Guo, Label-free aptasensor for ochratoxin A detection using SYBR Gold as a probe, Sens. Actuator B: Chem. 246 (2017) 647–652, https:// doi.org/10.1016/j.snb.2017.02.143. [37] S. Wang, Y. Zhang, G. Pang, Y. Zhang, S. Guo, Tuning the aggregation/disaggregation behavior of graphene quantum dots by structure-switching aptamer for high-sensitivity fluorescent ochratoxin A sensor, Anal. Chem. 89 (2017) 1704–1709, https://doi.org/10.1021/acs.analchem.6b03913. [38] Y. Zhao, R. Liu, W. Sun, L. Lv, Z. Guo, Ochratoxin A detection platform based on signal amplification by Exonuclease III and fluorescence quenching by gold nanoparticles, Sens. Actuator B: Chem. 255 (2018) 1640–1645, https://doi.org/10. 1016/j.snb.2017.08.176. [39] S. Ebrahim, M. Labeb, T. Abdel-Fattah, M. Soliman, CdTe quantum dots capped with different stabilizing agents for sensing of ochratoxin A, J. Lumin. 182 (2017)

154–159, https://doi.org/10.1016/j.jlumin.2016.09.038. [40] M.E. Flores-Flores, E. González-Peñas, An LC–MS/MS method for multi-mycotoxin quantification in cow milk, Food Chem. 218 (2017) 378–385, https://doi.org/10. 1016/j.foodchem.2016.09.101. Li Liu: Master student, college of Pharmaceutical Sciences, Zhejiang University, E-mail: 182,[email protected] Zheng Han: Vice director, institute for Agro-food Standards and Testing Technology, Shanghai Key Laboratory of Protected Horticultural Technology, Laboratory of Quality and Safety Risk Assessment for Agro-products (Shanghai), Ministry of Agriculture, Shanghai Academy of Agricultural Sciences, E-mail: [email protected] Yongjiang Wu: Professor, college of Pharmaceutical Sciences, Zhejiang University, E-mail: [email protected]

8