Chitosan-wrapped gold nanoparticles for hydrogen-bonding recognition and colorimetric determination of the antibiotic kanamycin

The authors describe a colorimetric assay for the quantitation of antibiotic kanamycin. It is based on hydrogen-bonding recognition capability of gold nanoparticles (AuNPs) in a chitosan matrix. Hydrogen-bonding interaction between kanamycin and chitosan induces the aggregation of the AuNPs, and this result in a color change of the AuNPs from wine red to blue. The ratio of the absorbance at 650 nm and 520 nm increases linearly over the 0.01 to 40 mu M kanamycin concentration range, and the detection limit is 8 nM (at an S/N ratio of 3). This low detection limit easily matches the maximum residue limits established by the European Union for milk (288 nM). Selectivity experiments revealed the assay to have a satisfactory specificity. It was applied to the determination of trace levels of kanamycin in (spiked) real samples. Results agreed well with those obtained by HPLC. The method does not require tedious detection procedure or sophisticated instrumentation.