A novel colorimetric aptasensor using gold nanoparticle for a highly sensitive and specific detection of oxytetracycline.

We have successfully developed a novel colorimetric aptasensor using gold nanoparticles for highly sensitive and specific detection of oxytetracycline (OTC), one of the most common antibacterial agents. A highly specific ssDNA aptamer that bind to OTC with high affinity was employed to discriminate other tetracyclines (TCs), such as doxycycline (DOX) and tetracycline (TET). Aggregation of AuNPs was specifically induced by desorption of the OTC binding aptamers (OBAs) from the surface of gold nanoparticles as a result of the aptamer-target interaction, leading to the color change from red to purple. The detection limit of OTC was enhanced up to 25 nM, which is 20-fold lower than the limit USA-EPA regulated, with two orders of magnitudes in its linear dynamic range by successful optimization on the amount of the aptamers, AuNPs, and salts. This colorimetric aptasensor is advantageous over the other conventional methods in terms of its simple signal generation and detection with the naked eye, which can be realized in on-site detection of antibacterial agents.