Poly-adenine-mediated spherical nucleic acids for interfacial recognition of kanamycin.

Abstract

Kanamycin fluorescence aptasensors were createdusing a series of di-block oligonucleotide modified gold nanoparticles with various lengths of poly-adenine. In the presence of kanamycin, the double strand structure of the aptamer-reporter strand complex is disrupted, and the dye-labelled reporter strand detaches from the surface of gold nanoparticles, resulting in fluorescence recovery (Ex/Em = 485/520nm). By adjusting the number of consecutive adenines, the programable aptamer density can be implemented on thegold nanoparticle surface, and the conformation of nucleic acid changed from lying-down to up-right. The apparent binding constant, binding kinetics, and limit of detection of theprepared aptasensors were carefully examined to explore the influence of surface density. Under the optimum condition, the aptasensor had a tenfold lower limit of detection than the thiolated aptamer modified one, as low as 23.6nM, when adi-block oligonucleotide with twenty consecutive adenines tailed. In addition, satisfactory recoveries ranging from 96.33 to 99.47% were achieved in spiked milk samples with relative standard deviation of 1.2-6.9% (n = 3). This surface density regulation strategy holds great promise in other aptamer-based interfacial recognition and sensing. Schematic presentation of di-block oligonucleotide modified gold nanoparticle with different surface densities and its kanamycin sensing application.