Construction of Fluorescence Sensing Platform on the Basis of Molybdenum Disulfide Nanosheet for the Detection of AFB₁

Xiaoqing Wen, Zichun Song, Jiuying Cui, Yan Li, Qianli Tang^*, Xianjiu Liao^*

Youjiang Medical University for Nationalities, Baise, China.

DOI: 10.4236/jbm.2023.112001                

Abstract

Purpose: Aflatoxin B₁ is the most common mycotoxin in cereal crops; it is of stronger toxicity and has a carcinogenic effect. In recent years, a series of fluorescence sensors constructed on the basis of MoS₂NS fluorescence quenching property have become a research hotspot. Therefore, we can construct a fast and simple analysis method with high specificity to detect AFB₁ by utilizing MoS₂NS, which can be effectively applied to food safety monitoring and clinical diagnosis. Method: In the current research, a fluorescence biosensor is developed on the basis of a new type of two-dimensional nano-material namely MoS₂NS applied for the detection of AFB₁. The fluorescence of Apt@AFB₁ can be quickly quenched by MoS₂NS through the fluorescence resonance energy transfer (FRET). When the target molecule AFB₁ exists, after the specificity binding between AFB₁ and aptamer, the Apt@AFB₁ loses its single stranded structure and is away from MoS₂NS, and the fluorescence of Apt®AFB₁ cannot be quenched effectively. Such sensing signals can be used to achieve the sensitive detection of AFB₁. Result: With this new method, under the optimized conditions, the AFB₁ is analyzed in the MoS₂NS/Apt®AFB₁ sensing platform. Within the dynamic range of 0.2 - 25 ng/mL, the sensing platform expresses a good linear response to the level of AFB₁ with the R² = 0.9964 and LOD as 90 pg/mL. This method is applied to detect the actual serum samples and soybean milk with the recovery rate of 93.10% - 107.23% and 95.15% - 102.60% separately, and it can be used in the quantitative detection under the interference of other mycotoxins in a relatively accurate way. Conclusion: It is proved that this new detection method can be used as a potential biosensor platform for the detection of AFB₁. This detection method features several advantages such as specificity, rapidness and low costs, which can meet the requirement of trace detection in clinical detection and food safety.

Keywords

MoS₂NS, Aptamer, Aflatoxin B₁, Fluorescence Sensing Analysis, Food Monitoring

1. Introduction

Aflatoxin is a secondary metabolite derived from fungus such as Aspergillusflavus and parasitic Aspergillus under the stressful condition. Although the amount of toxin produced by mold is very low, but the Aflatoxin is the mycotoxin with the strongest toxicity and Carcinogenicity founded by far [1], and the Aflatoxin B₁ (AFB₁) is a subtype of the Aflatoxin with the strongest toxicity [2]. The normal sterilization method of heating process cannot destroy its structure [3]. When a human eats crops containing a large amount of toxin such as seriously moldy peanuts, corn and bean at a time, acute poisoning could be easily caused, leading to diseases such as acute hepatitis, hemorrhagic necrosis and hepatocyte steatosis. If a human eats moldy cereal for a long time, liver chronic injuries would be caused, leading to the carcinogenesis and teratogenicity [4] [5].

Soybean milk is a special drink in China made from soybeans, which is well received among the population. If the soybean milk is made from moldy soybeans, the Aflatoxin is hard to be degraded during the preparation of soybean milk [2] [3]. The long-term drinking of such soybean milk will easily cause chronic poisoning of the human body. Therefore, the inspection of AFB₁ content in soybean products is of great importance. Countries of the world implement strict controls on the safety content of Aflatoxin in foods. China regulates that the content of Aflatoxin in soybean and its products shall not exceed 5 μg/mL [6]. The European Commission regulates the maximum pollution limit of crops and crop products, which is 4 μg/kg [7] for Aflatoxin and 2 μg/kg [8] for AFB₁ separately. Clinically, the toxicology analysis of food poisoning is also of great importance in the etiological treatment. Therefore, detecting the content of Aflatoxin in a fast, responsive and specific way is of great significance to ensure food safety, improve people’s quality of life and enhance the sustainable development of agriculture, which can also be applied effectively in the etiological diagnosis of clinical patients of acute food poisoning.

Molybdenum disulfide nanosheet (MoS₂NS) is a new type of two-dimensional nanomaterial, which is another hot research topic after graphene. It has an outstanding fluorescence-quenching feature and the absorbability of single-stranded nucleic acid [9] [10]. At present, a large number of studies have applied this feature to the detection of small molecules such as miRNA [11] and DNA [12] as well as the biological analysis of large molecules such as carcinoembryonic antigen, prostate specific antigen [13], and cardiac troponin T [14]. Such applications are conducive to the development of basic research in life science and the reform of medical clinical detection technology. In addition, the MoS₂NS features good dispersibility in water solution without surface-active agent or additional modification [12] [15]. It can also be prepared massively, which is a good kind of material for fluorescence sensing. The current research constructs a simple and rapid functional nano-biosensor MoS₂NS/Apt@AFB₁ on the basis of MoS₂NS and the aptamer Apt@AFB₁. With MoS₂NS as the fluorescence quenching carrier, Apt@AFB₁ is absorbed on the surface of MoS₂NS through the deposition and combination of π-π chemical bonds. Due to the Fluorescence Resonance Energy Transfer (FRET), the FAM fluorescent dye modified on the aptamer is quenched. When the target molecule AFB₁ exists, it can specifically bind to the aptamer to change the spatial construction of the aptamer, causing the MoS₂NS unable to effectively absorb the compound structure of Apt@AFB₁ and AFB₁. The fluorescence quenching effect is lost and the fluorescent dye can release signals. Through the intensity of fluorescence sensing signals, the content of AFB₁ can be detected effectively. This method is of possibility to open up a new path to the ultra-sensitive analysis of other mycotoxin or microorganisms. The sensing method constructed by the material of MoS₂NS is conductive to the application in clinical detection and food safety management and control.

2. Materials and Methods

2.1. Material

Tris-HCl buffer (20 mM Tris, 5 mM KCl, 5 mM MgCl₂, 100 mM NaCl, pH 7.4) is purchased from Sangon Biotech (Shanghai) Co., Ltd.; Molybdenum disulfide nanosheet is purchased from Nanjing XFNANO Materials Tech Co., Ltd.; Fetal bovine serum (FBS) is purchased from gibco Company (Grand Island, USA); The soybean milk sample is purchased from the canteen of the university; The water used in the experiments is all ultra-purified water; the AFB₁ aptamer sequence marked by FAM fluorescein is 5'-FAM-GTT GGG CAC GTG TTG TCT CTC TGT GTC TCG TGC CCT TCG CTA GGC CCA CA-3', which is composed by Sangon Biotech (Shanghai) Co., Ltd. All samples are reacted under the temperature of 37˚C. The fluorescence spectrophotometer (RF-6000, Shimadzu) is used to conduct fluorescence detection.

2.2. Methods

2.2.1. Preparation of MoS₂NS

Process the purchased water dispersing solution of molybdenum disulfide nanosheet with ultrasonic treatment for 1 h, then conduct centrifugation with 15,000 rpm for 15 min. Dissolve the centrifugal precipitates again into the ultra-purified water to obtain the black suspension liquid of MoS₂NS. Dilute the MoS₂NS into a solution with the concentration of 1 mg/mL as the reserve solution and store it under the temperature of 4˚C for later use [16]. Before its usage, process it with ultrasonic treatment for 20 min to ensure its good dispersibility.

2.2.2. Optimization of Experimental Conditions

1) Optimization of MoS₂NS Concentration: in order to determine the best fluorescence quenching effect of this sensing method, fix the concentration of the aptamer probe Apt@AFB₁ as 100 nM, then react the Apt@AFB₁ probe and the MoS₂NS with different concentration (0, 10, 20, 40, 60, 80, 100 and 120 μg/mL) at the temperature of 37˚C. Use fluorescence spectrophotometer to measure the fluorescence intensity and observe the fluorescence quenching conditions.

2) Optimization of Quenching Time: incubate 100 nM Apt@AFB₁ and the MoS₂NS with the final concentration of 80 μg/mL for a certain time (1, 2, 4, 6, 8, 10, 15, 30, 40, 60 and 120 min) under the temperature of 37˚C. After the incubation, use the fluorescence spectrophotometer to measure the fluorescence intensity and observe the fluorescence quenching conditions.

(3) Optimization of the Reaction Time of Apt@AFB₁ and AFB₁: incubate 100 nM Apt@AFB₁ probe with 10 ng/mL AFB₁ for different durations (0, 10, 20, 30, 40, 50 and 60 min) under the temperature of 37˚C. After the incubation, add the MoS₂NS with the concentration of 80 μg/mL into the reaction system and conduct incubation with fluctuation for 8 min, then use the fluorescence spectrophotometer to record the fluorescence intensity and observe the best reaction time of the sensing platform.

2.2.3. Fluorescence Analysis of the Sensing System

1) Feasibility analysis: the current research needs to discuss the response of fluorescence spectrometry with different experimental ingredients (Apt@AFB₁, MoS₂NS, AFB₁, MoS₂NS + Apt@AFB₁, and MoS₂NS + Apt@AFB₁ + AFB₁). After the incubation in accordance with the sensing scheme, record the emission spectrometry within the range of 505 - 650 nm at the excitation wavelength of 496 nm to analyze the detection feasibility of the MoS₂NS/Apt@AFB₁ sensing strategy.

2) Sensitivity analysis: Firstly, dissolve the AFB₁ powder into the methyl alcohol, and then dilute it with the Tris-HCl buffer into the AFB₁ solution with the concentration of 300 ng/mL as the reserve solution. Dilute the Apt@AFB₁ marked by FAM in the Tris-HCl buffer preliminarily to the solution with the concentration of 300 nM as the reserve solution, and store it in sub-package under the temperature of 4˚C. In order to evaluate the analysis and application capability of this sensing platform in actual samples, we conduct quantitative detection to the AFB₁. Under the best experimental conditions, prepare AFB₁ reserve solution with different volumes (2, 5, 10, 20, 40, 80, 140, 200, 250, 300, 400 and 600 μL) and mix them with 1 mL Apt@AFB₁ (300 nM) probe. Add Tris-HCl buffer to 2 mL and conduct fluctuation for 30 min under the temperature of 37˚C. After the fluctuation, add 0.24 mL MoS₂NS solution (1 mg/mL) and 0.76 mL Tris-HCl buffer, then continue the incubation of the reaction solution for 8 min. Finally, use the fluorescence spectrophotometer to measure the fluorescence intensity F, and record the fluorescence intensity of the samples without AFB₁ as F₀. Each concentration is measured in parallel for 3 times. Record the emission spectrometry within the range of 505 - 650 nm under the excitation wavelength of 496 nm. Use x coordinate to represent the concentration of AFB₁ and y coordinate to represent the fluorescence intensity of the reaction system to draw a standard curve, then calculate and analyze the linear range of the sensing detection and the lower limit of detection to explore the detection sensitivity of this sensing method.

2.2.4. Specificity Detection

In order to verify the selectivity of the MoS₂NS/Apt@AFB₁ sensing platform, we choose AFB₂, AFM₁, OTA and FB₁ and compare them with AFB₁. Prepare the AFB₁ with the concentration of 10 ng/mL and the AFB₂, AFM₁, OTA and FB₁ with the concentration of 20 ng/mL as the samples to be tested. In addition, mix 10 ng/mL of AFB₁ with 20 ng/mL of AFB₂, AFM₁, OTA and FB₁ separately to prepare the mixed solution as the sample to be tested, and prepare the blank control group without any toxin. Add 1 mL of Apt@AFB₁ probe solution with concentration of 300 nM into 1 mL of sample to be tested separately and fully mix them, and then conduct incubation with fluctuation under the temperature of 37˚C for 30 min. After the incubation, add 0.24 mL MoS₂NS (1 mg/mL) solution and 0.76 mL Tris-HCl buffer for 8min incubation reaction. Use fluorescence spectrophotometer to measure the fluorescence intensity at the wavelength of 517 nm under the excitation wavelength of 496 nm. This is repeated for 3 times in parallel for each sample, then compare and analyze all detected fluorescence intensity data.

2.2.5. Inspection of Samples

This is in order to evaluate the analysis and application capability of this sensing platform in actual serum samples and soybean milk. The serum samples to be tested are the 10% serum samples prepared by diluting FBS for 10 times. Then we prepare the soybean milk sample. Firstly, add 70% methyl alcohol into the purchased soybean milk (the volume ratio between soybean milk and 70% methyl alcohol is 1:2). Mix it evenly through shaking at room temperature for 30 min, then process ultrasonic treatment for 5min and centrifugation at 10,000 rpm for 10 min. The supernatant was obtained and filtered with 0.22 μm organic filter membrane. After the filtering, dilute the soybean milk for 10 times as the soybean milk residual solution. Then the detection performance of the MoS₂NS/Apt@AFB₁ fluorescence sensing platform in the actual serum and soybean milk samples will be examined. Under the best conditions, add AFB₁ with three types of concentrations (0.2, 5 and 15 ng/mL) into the 10% FBS and mix them well to prepare the sample to be tested, then detect it in accordance with the sensing strategy and record the fluorescence intensity. The same operation is conducted to prepare the soybean milk sample. Add AFB₁ with different concentrations (0.2, 5 and 15 ng/mL) into the soybean milk residual solution and mix them well, then conduct detection in accordance with the sensing strategy, record the fluorescence intensity and calculate the recovery rate. For the samples with each concentration, 5 experiments in parallel shall be set. The blank sample without toxin shall be set to record its fluorescent signal.

3. Results

3.1. Experiment Principle

MoS₂NS is capable to absorb ssDNA effectively. The current research uses the identifying probe of Apt@AFB₁. Apt@AFB₁ is the single-stranded deoxynucleotidyl modified with FAM fluorescein at the 5' end. The detection principle of MoS₂NS/Apt@AFB₁ fluorescence sensing platform constructed by the current research is as shown in Figure 1. If the target molecule AFB₁ exists, after the specificity binding between Apt@AFB₁ and the target molecule, when the MoS₂NS is added, the aptamer undergoes conformational change due to the binding of Apt@AFB₁ and AFB₁, causing the Van der Waals force between MoS₂NS and Apt@AFB₁ weaken, making it unable to absorb and leading to the conjugate of Apt@AFB₁ and AFB₁ dissociated. The conjugate is away from the quenching agent MoS₂NS. Therefore, the fluorescence resonance energy transfer (FRET) is blocked, and the fluorophore on the Apt@AFB₁ probe emits fluorescence. When the target molecule does not exist, due to the π-π deposition, MoS₂NS is capable to absorb Apt@AFB₁. When the spatial distance between MoS₂NS and FAM is less than 10 nm, the FRET occurs to quench the fluorescent signal of the fluorescent dye FAM. The MoS₂NS/Apt@AFB₁ achieves the sensitive quantitative monitoring to AFB₁ through fluorescence sensing, which is expected to be developed as the new type of fluorescence sensors in the application of AFB₁ detection.

3.2. Feasibility Analysis

As shown in Figure 2, we evaluate the feasibility of MoS₂NS/Apt@AFB₁ as the fluorescence sensing platform to detect AFB₁. Apt@AFB₁ is the identifying probe

Figure 1. Schematic illustration of the principle of the method for AFB₁ detection based on fluorescence quenching of Molybdenum disulfide nanosheets.

modified with FAM. When the sample to be tested only contains the ingredient of AFB₁, the fluorescent detection result indicates that a strong fluorescent signal appears at the position of 517 nm. In order to detect whether there is autofluorescence for the ingredients of quenching agent MoS₂NS and target molecule AFB₁, we separately conduct fluorescence analysis by regarding them as the separate ingredients in the samples to be tested. The detection results of the MoS₂NS sample and the AFB₁ sample indicate that their fluorescent signal intensity at the position of 517 nm is almost zero, which means that it will not interfere the specificity fluorescent detection of the sensing platform on AFB₁, and the detection result of MoS₂NS + Apt@AFB1 sample indicates that MoS₂NS, as the fluorescence quenching agent, can effectively quench the fluorescence of the probe after its binding with Apt@AFB₁. The background signal of the constructed sensing platform is relatively low, which is conductive to improve the accuracy of the AFB₁ detection. The MoS₂NS + Apt@AFB₁ + AFB₁ sample refers to the detection of AFB₁ in the complete sensing system. The detection result indicates that when the molecular target AFB₁ exists, a strong fluorescence emission peak appears at the position of 517 nm. This result shows that the sensing strategy of MoS₂NS/Apt@AFB₁ can effectively detect AFB₁, and this method is feasible.

3.3. Optimization of Experimental Conditions

In order to determine the best detection performance of the MoS₂NS/Apt@AFB₁ sensing platform, the concentration of MoS₂NS, fluorescence quenching time and the reaction time of Apt@AFB₁ probe and the target object AFB₁ shall be optimized. With MoS₂NS as the fluorescence quenching agent, whether the fluorophore FAM can be effectively quenched by MoS₂NS is the key to the effectiveness of this sensing method. The result is as shown in Figure 3(a). When the MoS₂NS with different concentrations exists, the fluorescence intensity of

Figure 2. Fluorescence spectra under different conditions: Apt@AFB₁, MoS₂NS, AFB₁, MoS₂NS + Apt@AFB₁ and MoS₂NS + Apt@AFB₁ + AFB₁ (with the presence of 25 ng/mL AFB₁). The concentrations of Apt@AFB₁ and MoS₂NS were 100 nM and 80 μg/mL, respectively.

Figure 3. (a) The optimization of MoS₂NS concentration. The concentration of Apt@AFB₁ was 100 nM. (b) The quenching efficiency of MoS₂NS. (c) Fluorescence Quenching time. The concentrations of Apt@AFB₁ and MoS₂NS were 100 nM and 80 μg/mL, respectively. (d) Reaction time of 100 nM Apt@AFB₁ and 25 ng/mL AFB₁, and then added 80 μg/mL MoS₂NS to continue reaction for 8 min.

fluorescent signal expressed by the Apt@AFB₁ aptamer with a fixed concentration of 100 nM is constantly weakening as the MoS₂NS concentration increases. The fluorescence intensity reaches its minimum value when the MoS₂NS concentration reaches 80 μg/mL, as shown in Figure 3(b). MoS₂NS quenches 96.9% of the fluorescent signals. The background signal is very low. This only existed background fluorescent signal is probably caused by the individual Apt@AFB₁ probes which cannot be absorbed on MoS₂NS effectively due to their voluntary changes on secondary structure. But such phenomenon is very rare, which will not produce obvious interference to the detection. In terms of the optimization of the fluorescence quenching reaction time, as shown in Figure 3(c), the fluorescence of Apt@AFB₁ probe can be quenched by MoS₂NS rapidly. After 8 min, the fluorescence quenching effect reaches the lowest value and the quenching system tends to be stable until 120 min. The best reaction time of Apt@AFB₁ and AFB₁ is as shown in Figure 3(d). When the reaction time reaches 30 min, the detected fluorescent signal intensity reaches the highest level and the fluorescence intensity remains unchanged until 60 min. In summary, the best reaction condition of this sensing platform is to use MoS₂NS with the concentration of 80 μg/mL with the quenching time of 8 min and the reaction time of probe and target material of 30 min. Such conditions will be applied to the subsequent experiments. Compared with the detection and analysis time of sensors with MoS₂NS as the quenching material reported by other references [11] [15] [16] [17], their quenching time is relatively close. This sensing platform even has a shorter quenching time and simple operation. In terms of the sensing system detection, MoS₂NS has a high quenching efficiency and a stable quenching performance. The fluorescent signals can be expressed stably, which meet the experimental requirement of signal detection and will not cause bias in detection results.

3.4. Sensitivity Analysis

Analyzing from the perspective of detection sensitivity, we research on the relations between the fluorescent signal intensity and the AFB₁ concentration in the reaction system under the best reaction conditions. The result is as shown in Figure 4. When the AFB₁ concentration is within the range of 0.2 - 25 ng/mL, the value of fluorescence intensity △F (△F = F − F₀) is positively correlated with the concentration of AFB₁. The linear regression equation is △F = 1093.142X − 71.028 and the correlation R² = 0.9964. As the increase of AFB₁ concentration, the fluorescent intensity of the sensors is significantly enhanced. The limit of detection (LOD) can be calculated by the ratio of the standard deviation of fluorescence intensity of three-time blank sample to the slope of the standard curve, which is 90 pg/mL. This MoS₂NS/Apt@AFB₁ sensing platform has sensitive effect in the detection of AFB₁, which can achieve the quantitative detection of AFB₁ molecules by monitoring the changes of fluorescent signal intensity. Compared with methods reported by related research, the electrochemical detection and surface-enhanced Raman scattering (SERS) has a low LOD, but the

Figure 4. (a) Fluorescence intensity spectra of AFB₁ with different concentrations. (b) Standard curve of fluorescence intensities against the concentrations of AFB₁. The concentrations of Apt@AFB₁ and MoS₂NS were 100 nM and 80 μg/mL, respectively. Reaction on 37˚C for 30 min, and then added 80 μg/mL MoS₂NS to continue reaction for 8 min.

electrochemical detection method has a long pretreatment time and many steps [8] [18] [19]. The SERS experiment is time-consuming [20] [21]. While as the traditional direction method, the high-performance liquid chromatography (HPLC) has high costs, expensive daily maintenance costs and complicated pretreatment [7] [22]. The MoS₂NS/Apt@AFB₁ sensing platform constructed by the current research has an outstanding LOD on AFB₁. Comprehensively compared, this method has relatively high cost performance. In addition, the sensitivity of this method can meet the detection requirement of AFB₁.

3.5. Specificity Analysis

Analyzing in terms of the detection specificity, we examine the selectivity of the constructed MoS₂NS/Apt@AFB₁ sensing platform. As shown in Figure 5, when the target molecule AFB₁ exists, a strong fluorescent signal is detected by the sensing platform. Simultaneously, in terms of some common interfering substance existing in the nature, we identify and detect some other mycotoxins such as AFB₂, AFM₁, OTA and FB₁. When these mycotoxins exist, the sensing platform does not detect an obvious fluorescent signal response, while in the mixed solution (AFB₁, AFB₂, AFM₁, OTA and FB₁), the MoS₂NS/Apt@AFB₁ sensing platform can detect the content of existed AFB₁ accurately, indicating that the MoS₂NS/Apt@AFB₁ sensors can distinguish other impurities and conduct specificity detection to AFB₁ in complex samples. This result shows that this fluorescence sensing method has the potential possibility in the application of complex sample analysis.

3.6. Sensing Application in Actual Samples

Serum is the clinical detection sample with easy access. To detect the existence of AFB₁ is serum can assist the clinical etiological diagnosis and analysis on acute

Figure 5. The selectivity of the Fluorescence assay. The concentration of AFB₁ was 10 ng/mL, nonspecific molecules were all 20 ng/mL and the concentration of mixed liquid：AFB₁ was 10 ng/mL, AFB₂,AFM₁,OTA and FB₁ were all 20 ng/mL. Blank sample was without AFB₁.

food poisoning for patients. Aspergillusflavus is easy to pollute bean crops and produce Aflatoxin through metabolism. If the soybean milk, a soybean product, has AFB₁, it is hard to degrade it through normal food processing. Therefore, we use the MoS₂NS/Apt@AFB₁ sensor to conduct AFB₁ standard addition recovery test on the serum samples and the food samples of soybean milk. Under the best experimental condition, add AFB₁ with the concentration of 0.2, 5 and 15 ng/mL into the serum and soybean milk samples and then conduct detection. The detection result of the sensor constructed in the current experiment is as shown in Table 1. The standard addition recovery rate of the serum sample is 93.10% - 107.23% and the relative standard deviation (RSD) is 2.15% - 4.42%. The AFB₁ standard addition recovery rate of the soybean milk sample is 95.15% - 102.60% and the relative standard deviation (RSD) is 1.78% - 3.98%. Therefore, it may be judged that this sensing method is applicable for the analysis of real biological sample with interference. This method has a good reproducibility, which can satisfy the requirement of actual application.

4. Conclusion

As a common contaminant in crops, AFB₁ is the toxin with great harm to the human body, which is listed by the International Agency for Research on Cancer (IARC) as a Group 1 Carcinogen [3]. Its main source is the metabolites derived from Aspergillusflavus after polluting grain crops with high starch contents, such as soybean, peanut and corn. If a patient has acute food poisoning symptoms or chronic liver diseases with suspected relations to the Aflatoxin, it is needed to conduct quick etiological diagnosis. At the same time, food safety supervision and management departments also need a simple and fast detection method to control the food safety and to prevent diseases from entering through the mouth. The current research constructed a biosensor on the basis of the new type of nano-material namely MoS₂NS. The detection strategy is as follows: With Apt@AFB₁ as the biological probe and MoS₂NS as the quenching receptor of fluorescent signals, the fluorescence signal is released by AFB₁ by being specifically bound to Apt@AFB₁ and moving away from MoS₂NS together leading to blocking FRET. When the AFB₁ is within the range of 0.2 - 25 ng/mL, the

Table 1. Determination results of AFB₁ in real sample analysis (n = 5)

fluorescent signal intensity detected by the MoS₂NS/Apt@AFB₁ sensor has good linear relations with the level of AFB₁, and the LOD is 90 pg/mL. The experimental recovery rate of serum samples and soybean milk samples with different concentrations of AFB₁ added is satisfactory. The current research achieves the rapid and sensitive quantitative detection of AFB₁ with specificity for serum and soybean milk. Aflatoxins are currently detected using thin-layer chromatography (LC) [23] [24], high performance liquid chromatography (HPLC) [25] [26] [27] [28], and enzyme linked immunosorbent assays (ELISA) [29] [30]. The above detection methods have several drawbacks, including cumbersome operation, expensive detection instruments and equipment, and time-consuming and labor-intensive issues. Compared with traditional methods, this sensing method has characteristics such as low costs and quick analysis time. Therefore, MoS₂NS/Apt@AFB₁ is a convenient, sensitive and stable sensing platform, featuring great potential of application in fields such as food safety inspection, environmental monitoring and clinical detection.

Fund Program

We gratefully acknowledge the financial support of the Guangxi Medical High-level Leading Talents Training 139 Project (GWKJ2018-22), Special Funding for Guangxi Special Experts (GRCT2019-13), Innovation Project of Guangxi Postgraduate Education (Project No.: JGY2021219, JGY2020170).

Conflicts of Interest

The authors declare no conflicts of interest regarding the publication of this paper.

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