Aflatoxin B1 (AFB1) is a mycotoxin produced as a secondary metabolite by filamentous fungi such as Aspergillus flavus and Aspergillus parasiticus. Among other illness-related issues attributed to AFB1, according to the International Agency for Research on Cancer, there is evidence that it is carcinogenic. This mycotoxin proliferates mainly in nuts, spices, milk, and cereals, such as corn, rice, and amaranth. For that reason, many countries have set rules about the maximum AFB1 levels allowed in different food items (around the ppb range).

The standard mycotoxin detection protocols rely on liquid or gas chromatography methods, in many cases coupled to mass spectrometry. These methods can detect AFB1 concentrations in the range of 1-20 ppt, but they are not very accessible, require tedious sample preparation, highly trained personnel, and expensive equipment. These requirements narrow their applicability in quality control by farmers and small to medium businesses, so novel sensors that overcome these drawbacks are needed.

Herein, we present the development of a detection system based on gold nanotriangles (AuNTs) functionalized with mercaptopropionic acid (MPA) to induce the adsorption of the mycotoxin. Once the AFB1 is close to the AuNTs, these nanostructures' excellent optical properties make them act as nanoantennas capable of enhancing the mycotoxin's Raman signals in solution without the need of any additional reporter. A multivariate analysis method based on partial least squares (PLS) regression has also been implemented to process the surface-enhanced Raman scattering (SERS) spectra. Very promising results have been obtained, being able to selectively discriminate AFB1 content in amaranth extract solutions down to the ppb level.

Mary Licuona

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