Aflatoxin B1 (AFB1) is the most toxic in naturally contaminated foods (Wang et al., 2018), which can cause liver cancer and even death to human beings and animals (Bashiry et al., 2021; Ahmad Al-Jaal et al., 2019; Buszewska-Forajta et al., 2020). Considering its carcinogenic effects on human beings, many countries have established the maximum level of AFB1 between 0.05 and 20 ng mL− 1 in all food and agriculture products (Babu et al., 2011). The European Union stipulates that the content of aflatoxin B1 in human consumer goods shall not exceed 2 µg kg− 1 (Goud et al., 2016). The research on food safety related to aflatoxin B1 has attracted the favor of the majority of researchers and made a series of research progress, such as chromatography and immunoassay (Xing et al., 2020; Xia et al., 2018; Xiong et al., 2018). The methods mentioned above can accurately and sensitively detecttion aflatoxin B1, but the defects of time-consuming and high detection cost limit their development (Xue et al., 2019; Xiong et al., 2020). Therefore, it is urgent to develop an efficient AFB1 detection method (Wang et al., 2019).
Since the advent of aptamers in the 1990s, researchers have worked hard to the research of aptamers with many advantages (Liu et al., 2018; Chen et al., 2017a). The special spatial configuration of aptamers is easy to form different three-dimensional structures, such as spiral, hairpin, stem ring, convex ring and other structures, which can easily capture the target based on the interaction of various functional groups (Yang et al., 2018; Barthelmebs et al., 2011; Zhang et al., 2012). Compared with antibody detection, the aptamer obtained by screening are easier to prepare and store (Hansen et al., 2006; Wang et al., 2016a). Nowadays, Various aptasensor methods came into being and were successfully applied to the efficient detection of aflatoxin B1, such as colorimetric, electrochemistry, and fluorescent aptasensors (Hao et al., 2018; Seok et al., 2015; Luo et al., 2019; Zheng et al., 2016). Among them, the colorimetric system (3,3’,5,5’-tetramethylbenzidine (TMB) and H2O2) mediated by F3O4 is considered to be one of the most promising technologies for the determination of AFB1 because it can usually change the color in the process of colorimetric analysis (Woo et al., 2013; Fu et al., 2018). Some reports have proved that TMB-H2O2 colorimetric system has high light-heat conversion efficiency when activated by near infrared (NIR), which means that TMB-H2O2 system has the potential of AFB1 detection by photothermal analysis (Luo et al., 2020b). The previous research results of our research group have proved that the enzyme like catalytic activity of Au@Fe3O4 is 1.5 times that of Fe3O4, which greatly increases the sensitivity of the sensor (Wang et al., 2016b). However, the above single detection mode will inevitably be affected by the possible simultaneous interferences, different operators, instruments and non-standard detection processes. The dual-mode sensing strategy not only has the inherent characteristics of each response mode, but also can mutually verify the detection results obtained by different modes, which will effectively improve the accuracy and reliability of detection (Fu et al., 2021).
The electrochemical-photothermal dual-mode not only has two mode signals, but also has the advantages of fast response, high sensitivity, low cost and simple operation. Here, a versatile aptasening chip researched for the photothermal and electrochemical dual modes sensitive detection of AFB1 in this work. Compared with single-mode electrochemical signal, photothermal signal can effectively improve the accuracy and reliability of detection, and achieve mutual verification and joint use. ITO conductive glass modified AuNPs nano-layer (ITO/AuNPs) can not only effectively improve the electronic conductivity, but also effectively link the thiol terminal modified aptamer. The aptasensor fabricated by loading the Au@Fe3O4 onto the ITO/AuNPs surface obtained by hybridization of aptamer and cDNA. After adding AFB1, aptamer tends to form aptamer-AFB1 complex, resulting in part of Au@Fe3O4 falling off the ITO/AuNPs surface and entering the reaction solution. TMB-H2O2 system with magnetically collected Au@Fe3O4 produces color change under the catalysis of Au@Fe3O4 and photothermal signal analysis under the excitation of near infrared light realized with the help of thermometer. In addition, combined with electrochemical impedance spectroscopy (EIS) analysis with ITO/AuNPs electrode, a dual mode provided for AFB1 detection.