*Article* **Development of an Immunofluorescence Assay Module for Determination of the Mycotoxin Zearalenone in Water**

**Borbála Gémes <sup>1</sup> , Eszter Takács <sup>1</sup> , Patrik Gádoros <sup>2</sup> , Attila Barócsi <sup>2</sup> , László Kocsányi <sup>2</sup> , Sándor Lenk <sup>2</sup> , Attila Csákányi <sup>3</sup> , Szabolcs Kautny <sup>3</sup> , László Domján 3 , Gábor Szarvas <sup>3</sup> , Nóra Adányi <sup>4</sup> , Alexei Nabok <sup>5</sup> , Mária Mörtl <sup>1</sup> and András Székács 1,\***


**Abstract:** Project Aquafluosense is designed to develop prototypes for a fluorescence-based instrumentation setup for in situ measurements of several characteristic parameters of water quality. In the scope of the project an enzyme-linked fluorescent immunoassay (ELFIA) method has been developed for the detection of several environmental xenobiotics, including mycotoxin zearalenone (ZON). ZON, produced by several plant pathogenic *Fusarium* species, has recently been identified as an emerging pollutant in surface water, presenting a hazard to aquatic ecosystems. Due to its physico-chemical properties, detection of ZON at low concentrations in surface water is a challenging task. The 96-well microplate-based fluorescence instrument is capable of detecting ZON in the concentration range of 0.09–400 ng/mL. The sensitivity and accuracy of the analytical method has been demonstrated by a comparative assessment with detection by high-performance liquid chromatography and by total internal reflection ellipsometry. The limit of detection of the method, 0.09 ng/mL, falls in the low range compared to the other reported immunoassays, but the main advantage of this ELFIA method is its efficacy in combined in situ applications for determination of various important water quality parameters detectable by induced fluorimerty—e.g., total organic carbon content, algal density or the level of other organic micropollutants detectable by immunofluorimetry. In addition, the immunofluorescence module can readily be expanded to other target analytes if proper antibodies are available for detection.

**Keywords:** zearalenone; mycotoxin; competitive immunoassay; fluorescence detection; high-performance liquid chromatography; total internal reflection ellipsometry

**Key Contribution:** An in situ detection module with a dynamic detection range between 0.09 and 400 ng/mL was developed for zearalenone. The immunofluorescence method and module, as well as the instrument prototype, constitute a part of the Aquafluosense modular instrument family for determination of characteristic water parameters and contaminants.

**Citation:** Gémes, B.; Takács, E.; Gádoros, P.; Barócsi, A.; Kocsányi, L.; Lenk, S.; Csákányi, A.; Kautny, S.; Domján, L.; Szarvas, G.; et al. Development of an Immunofluorescence Assay Module for Determination of the Mycotoxin Zearalenone in Water. *Toxins* **2021**, *13*, 182. https://doi.org/10.3390/ toxins13030182

Received: 10 February 2021 Accepted: 24 February 2021 Published: 2 March 2021

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