Aptamer based fluorometric determination of kanamycin using double-stranded DNA and carbon nanotubes

The authors describe a fluorometric assay for the antibiotic kanamycin that is making use of a fluorescein-labeled aptamer against kanamycin and carbon nanotubes (CNTs). It is found that CNTs do not quench the fluorescence of the duplex formed between FAM-labeled aptamer and its complementary DNA (cDNA). However, if kanamycin is added, it will bind to the aptamer, and this leads to dehybridization of the duplex upon which the fluorescence of the label is quenched by the CNTs present in solution. The method has an analytical range that extends from 1.0 to 50 nmol L-1 of kanamycin, and the detection limit is 0.4 nmol L-1. It was successfully employed to the detection of kanamycin in (spiked) milk samples and gave good recoveries.