“Naked” gold nanoparticles as colorimetric reporters for biogenic amine detection

Biogenic amines (BA) are present in fermented foods and beverages. As their high intake may produce adverse reactions in humans, the control of BA concentration is advisable. Simple, rapid, point-of-use analytical platforms are needed because traditional methods for the detection and quantification of BAs are expensive and time-consuming. In this work a colorimetric assay based on “naked” gold nanoparticles (AuNPs) which is sensitive to BAs is developed. The detection is based on the AuNPs aggregation upon binding of the analytes. Aggregation induced a change in color of the solution from burgundy to grey/blue. Concomitantly, UV–vis absorption spectra of AuNPs showed that the characteristic absorption peak at 520 nm decreased and a new absorption peak was generated at 650 nm. So, analyte detection can be achieved by eye and quantification can be simply obtained by using a spectrometer. The response characteristics of the assay have been determined using histamine (His) as BA model molecule. The assay has a limit of detection of 0.2 μM. The BA content in wine was determined by the assay. Finally, as AuNPs have been prepared by LAL in absence of any capping agent, a mechanism of aggregation based on the direct interaction between the amine groups of His with gold is proposed.