One-step rapid detection of fumonisin B₁, dexyonivalenol and zearalenone in grains

Highlights

• One-stop rapid detection of FB₁, DON and ZEN in different samples has been developed.

• The cut-off limits of this strip were 60/12.5/6 ng/mL for FB₁, DON and ZEN, respectively.

• Our designed multiplex strips can serve as potential multi-POCT platform for analysis.

Abstract

Mycotoxins are a class of secondary metabolites produced by filamentous fungi that are harmful to humans and animals. Here, a multiplex immunochromatographic assay was reported, which is based on 25 nm colloidal gold for simultaneous qualitative detection of fumonisin B₁ (FB₁), deoxynivalenol (DON) and zearalenone (ZEN) in wheat and corn samples. After conditions optimization, the immunochromatographic strip has high sensitivity. The visual detection limits of the immunochromatographic test strips for FB₁, DON, and ZEN reached 60, 12.5 and 6 ng/mL, respectively. In addition, the immunochromatographic strip has high specificity, no reaction to each other, or no cross-reactivity with ochratoxin A (OTA) and aflatoxin B₁ (AFB₁). Furthermore, eighteen samples (including corn and wheat) were tested using the test strips and verified by liquid chromatography-mass spectrometry (LC-MS/MS). The results of strips were found to be consistent with those of liquid chromatography-mass spectrometry (LC-MS/MS). In short, this work demonstrates that the spherical colloidal gold-based immunochromatographic test strip we developed can be used to quickly and simultaneously monitor the existence of multiple mycotoxins in agricultural food samples.

Introduction

Mycotoxins are a class of secondary metabolites produced by filamentous fungi that can accumulate in humans and animals. They are carcinogenesis, teratogenic, mutagenicity and immunotoxicity which harm to humans and animals (Tittlemier et al., 2019). The distribution of mycotoxins is widespread, mainly contaminating agricultural products such as wheat, corn, feed and foods that people rely on for daily survival (Gil-Serna, Garcia-Diaz, Vazquez, Gonzalez-Jaen, & Patino, 2019; Pereira, Cunha, & Fernandes, 2019; Viegas et al., 2019). Especially in some developing countries, food production and quality control are not strict, which is likely to cause mycotoxin contamination. As reported, mycotoxins are stable and are not easily destroyed by physical or chemical means (Hou, Ma, Meng, Xu, & He, 2019). Many countries and international organizations have set the maximum residue limits for FB1, DON, and ZEN, respectively. China has set the maximum residue limits as 60 mg/kg for the sum of fumonisin (FB₁, FB₂) in corn and its processed products, 1 mg/kg for deoxynivalenol in grain and its processed products, and 60 μg/kg for zearalenone in grain and its processed products (Ren et al., 2015). Although researchers have tried their best to reduce the exposure of mycotoxins and focused on the degradation methods, the pollution is still inevitable (Duan, Li, Shao, Huang, & Xiong, 2019). The agricultural products and food contaminated with mycotoxins is still one of the major safety problems in the world.

In order to prevent and detect mycotoxins in raw materials and products before and after food processing, researchers have made many efforts to develop different detection methods, mainly including chromatography and immunology (Tittlemier et al., 2019). Chromatography-based methods include gas phase (GC), liquid chromatography, high performance liquid chromatography (N. Wang et al., 2019) (HPLC) and more commonly used liquid chromatography-mass spectrometry (De Paepe et al., 2019) (Hidalgo-Ruiz, Romero-Gonzalez, Martinez Vidal, & Garrido Frenich, 2019) (LC-MS/MS). Chromatography is highly accurate, but it is time consuming and requires complicate sample processing, expensive instrumentation as well as professional operators (Z. Zhang et al., 2018). Immunological methods are based on antigen and antibody reactions, including the most widely used enzyme-linked immunosorbent assay (ELISA), some new sensitive detection methods based on fluorescence (Z. Tang et al., 2019; Zhang et al., 2019), electrochemistry (Luo et al., 2019; Ma et al., 2019; Selvolini et al., 2019) and chemiluminescence (Yao et al., 2019). Although, these methods are highly sensitive, they are not suitable for large batch field detection. The emergence of immunochromatography technology provides a rapid and accurate detection method to be used in the field.

Immunochromatography has been widely used in various fields such as clinical diagnosis (J. M. Zhu et al., 2011), drug residue analysis (Fang et al., 2019; C.; Liu et al., 2011; Y.; Liu et al., 2019), environmental analysis (Bu et al., 2018; M.; Zhu et al., 2014) and food safety detection (Hu et al., 2020; Q.; Wang et al., 2020; Xu et al., 2019; M.; Zhang et al., 2018), because it is rapid, simply, low cost and it does not rely on professional techniques or instruments (Song et al., 2014). Previous studies have shown that certain agricultural products are not only contaminated with one mycotoxin, but may also be contaminated with several mycotoxins (Duan et al., 2019; D.; Wang et al., 2019). For example, wheat is easily contaminated with zearalenone (ZEN), fumonisin B₁ (FB₁) and deoxynivalenol (DON) (Ul Hassan, Al Thani, Balmas, Migheli, & Jaoua, 2019). The routine single mycotoxin test of a single sample does not completely prevent the harm to humans and animals (Duan et al., 2019). The use of multiple single-type test strips alone increases the cost and time (Duan et al., 2019). Therefore, it is necessary to develop a simple and rapid method for simultaneously detecting various mycotoxins. Although many different new nanomaterial have appeared in immunochromatography (Foubert et al., 2017; Li et al., 2018; X.; Tang et al., 2017; X.; Zhang et al., 2018), colloidal gold nanoparticles (AuNPs) is widely used in testing due to its advantages of stability, easy synthesis and low cost. Nowadays, colloidal gold is still the raw material in many commercial kits.

We have reported immunochromatographic test strips for simultaneous detection of ZEN and FB₁ based on 25 nm colloidal gold in previous study (Y.K. Wang, Shi, et al., 2013), which is more sensitive than other reports (Huang et al., 2012; Sun et al., 2014; Xian Zhang et al., 2018). It is found that 25 nm colloidal gold nanoparticles were confirmed being able to improve performance significantly. Based on our previous results, we developed an immunochromatographic test strip for simultaneous detection of three mycotoxins (FB₁, DON and ZEN). The detection limits of FB₁, DON, and ZEN were 60, 12.5 and 6 ng/mL, respectively. The developed assay has been applied for the determination of mycotoxins in spiked and naturally contaminated cereal samples. The results showed strong agreement with LC-MS/MS detection method.