Rapid Apta-Chromogenic Detection Method for Nitrofuran Metabolite Determination

Nitrofuran (NF) contamination in food products is a global problem resulting in the banned utilization and importation of nitrofuran contaminated products. A novel chromogenic detection method using a specific DNA aptamer with high affinity and specificity to nitrofurans was developed. Single-stranded DNA aptamers specific to nitrofuran metabolites, including 3-amino-2-oxazolidinone (AOZ), 3-amino-5-methylmorpholino-2-oxazolidinone (AMOZ), and 1-aminohydantoin (AHD), were isolated using magnetic bead-SELEX. The colorimetric detection of nitrofurans using gold nanoparticles (AuNPs) exhibited an AOZ detection range of 0.01-0.06 ppb with a limit of detection (LOD) of 0.03 ppb. At the same time, this system could detect AMOZ and AHD at a range of 0.06 ppb and 10 ppb, respectively. The fast nitrofuran extraction method was optimized for food, such as fish tissues and honey, adjusted to be completed within 3-6 h. This novel apta-chromogenic detection method could detect NF metabolites with a sensitivity below the minimum required performance limit (MPRL). This analysis will be valuable for screening, with a shortened time of detection for aquaculture products such as shrimp and fish muscle tissues.

Quantum Dot Nanobeads as Multicolor Labels for Simultaneous Multiplex Immunochromatographic Detection of Four Nitrofuran Metabolites in Aquatic Products

A multicolor immunochromatographic assay platform based on quantum dot nanobeads (QBs) for the rapid and simultaneous detection of nitrofuran metabolites in different aquatic products is documented. These metabolites include 3-amino-2-oxazolidinone (AOZ), 1-aminohydantoin (AHD), semicarbazide (SEM), and 3-amino-5-morpholino-methyl-1,3-oxazolidinone (AMOZ). QBs with emission colors of red, yellow, green, and orange were employed and functionalized with the corresponding antibodies to each analyte to develop a multicolor channel. The visual detection limits (cutoff values) of our method for AOZ, AHD, SEM, and AMOZ reached up to 50 ng/mL, which were 2, 20, 20, and 20 times lower than those of traditional colloidal gold test strips, respectively. The test strip is capable of detection within 10 min in real samples while still achieving good stability and specificity. These results demonstrate that the developed multicolor immunochromatographic assay platform is a promising technique for multiplex, highly sensitive, and on-site detection of nitrofuran metabolites.

Presence of nitrofurans and their metabolites in gelatine

Following the detection of semicarbazide (SEM) in gelatine by Italian Authorities, at levels exceeding by three times the reference point for action (RPA) of 1 μg/kg, set out by Commission Regulation (EU) 2019/1871 for nitrofurans and their metabolites, the European Commission mandated EFSA to investigate the available sources of nitrofurans and their metabolites in gelatine. European Commission also asked EFSA to provide approaches that would distinguish SEM occurring due to illegal treatment with nitrofurazone from SEM produced during food processing. The literature indicates that SEM, both free and bound to macromolecules, could occur also in food products such as gelatine, during food processing, arising from the use of disinfecting agents and/or from reactions of various food components and, therefore, SEM cannot be considered as an unequivocal marker of the abuse of nitrofurazone in animal production. It is recommended to investigate in more detail which processing conditions lead to the formation of SEM in gelatine during its production and what levels can be found. One potential approach to distinguishing between SEM from nitrofurazone and SEM from other sources in food products, such as gelatine, might be based on determining the ratio of bound:free SEM in a sample of gelatine. However, whether the ratio of bound:free SEM would unequivocally distinguish between SEM arising from nitrofurazone abuse or from other sources still needs to be demonstrated.