Gentamicin is an aminoglycoside antibiotic that is used to treat serious bacterial infections in humans and livestock. Consequently, there are concerns that residues of gentamicin in animal products could lead to the development of gentamicin resistant bacteria in humans. The maximum residue limits allowed in milk and other animal products are below 100 ppb, so it is necessary to have a detection method that can detect very low concentrations of the drug. The goal of this study was to develop a simple and rapid colorimetric method for gentamicin detection using cysteamine modified gold nanoparticles (AuNPs). AuNPs aggregate in the presence of gentamicin, which results in a visible color change. Adding cysteamine enhanced the ability of the AuNPs to aggregate, allowing lower concentrations of gentamicin to be detected. The modified AuNPs were capable of detecting gentamicin concentrations as low as 18.5 ppb in water, which could be observed with the naked eye and quantified using UV-vis spectroscopy. The detection was also successful in the presence of common food components. After a simple pre-treatment, we could detect at least 149 ppb gentamicin in skim milk within 30 minutes for a set of 10 samples. This study demonstrated the great capability of our method for the rapid screening and quantification of gentamicin residues in complex food matrices.

Colorimetric detection of gentamicin in milk using functionalized gold nanoparticles

253rd National Meeting (2017)

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