Luminescent molecularly imprinted polymer nanocomposites for emission intensity and lifetime rapid sensing of tenuazonic acid mycotoxin

Abstract

Tenuazonic acid ((5S)-3-acetyl-5-[(2S)-butan-2-yl]-4-hydroxy-2,5-dihydro-1H-pyrrol-2-one, TeA) is a widespread Alternaria fungi mycotoxin in food produce. This toxin may be allergenic and provoke hay fever and asthma. Therefore, rapid methods to selectively detect TeA are needed. With this aim, we have engineered a novel trifunctional (red-luminescent, polymerizable, TeA-sensitive) ruthenium(II)-bipyridyl complex with 2,2′-biimidazole. Its peripheral N–H moieties recognize the enolate form of 1,3-dicarbonyl compounds (including TeA) in partially aqueous media. Such a binding decreases the luminescence intensity and lifetime (0.2 μs) of the Ru(II) probe. The probe also bears acrylate groups that allow radical copolymerization with methacrylamide and ethylene glycol dimethacrylate in the presence of TeA, to yield 9-nm thick luminescent molecularly imprinted polymer (MIP) shells onto 200-nm silica cores. The SiO2@Ru-MIP nanocomposite displays a very fast response (<5 s) suitable for real-time detection of TeA. No cross-sensitivity to other common food mycotoxins that also contain a β-hydroxycarbonyl moiety (alternariol, β-zeranol, cyclopiazonic acid) is observed. Detection limits of 63.8 μg L⁻1 and 75.2 μg L⁻1 under steady-state and time-resolved luminescence detection, respectively, have been measured without further optimization. The use of emission lifetime variations to monitor the levels of a target analyte has never been reported for a luminescent MIP-based sensor.