A polyA aptamer-based label-free colorimetric biosensor for the detection of kanamycin in human serum

A novel colorimetric assay for the sensitive detection of kanamycin (KAN) is described. In this study, for the first time, a polyA aptamer (polyA apt) and gold nanoparticles (AuNPs) were used to construct a nano-bio platform for the detection of kanamycin. The polyA apt, adsorbed on the AuNPs, can bind to the analyte while inhibiting non-specific interactions. Poly(diallyl dimethyl ammonium chloride) (PDDA) is an aggregating agent that, in combination with the aptamer, hinders the aggregation of the AuNPs. Introduction of KAN into the assay solution liberates PDDA from the AuNPs and, as aggregation inhibition is no longer observed, the color of the bioassay solution changes from red to blue. In the absence and presence of KAN, significant and distinctive optical absorbance signals (measured at 520 and 690 nm) are produced in the assay solution. This bioassay does not require a lengthy preparation and can be implemented in a few minutes without the need for expensive instruments or a skilled user. The detection of KAN was linear in the concentration range of 1-300 nM with a limit of detection of 0.05 nM (S/N = 3). The obtained detection limit was significantly better than those of previously reported colorimetric aptasensors. The fabricated aptasensor can detect KAN selectively in the presence of other concomitant species in the complex matrix of human serum. Therefore, it can be used for the practical monitoring of KAN in clinical applications. This aptasensor can be used as a promising tool for accurately and reliably detecting the concentration of kanamycin in serum which is very important to prevent the toxic effects caused by its presence in animal-derived foods.