Gentamicin induced formation of gold nanoparticles as an assay protocol for its detection

A quick method for the visualization and estimation of gentamicin up to a concentration of 10 mg L-1 is formulated. Since gentamicin lacks any chromophore or fluorophore, direct spectro photometric or fluorometric estimation cannot be used for the detection of this widely used antibiotic. Here we explored the ability of gentamicin to reduce gold ions into gold nanoparticles. The formation of the wine red colored gentamicin stabilized gold colloid (Au-genta) from the colorless aqueous gentamicin solution made it possible its detection with both naked eye and spectrophotometrically. This method does not need any tedious chemical derivatization or fluorescent labeling steps or the use of any costly instrumental analysis techniques. It also offers comparatively better sensitivity (2.5 mg L-1) than the other reported methods (390 mg L-1 for gentamicin derivatization with ninhydrin and 1000 mg L-1 with o-phthalaldehyde).