Antioxidant-Capped Gold Nanoparticles for Colorimetric Detection of Kanamycin

In the development of aptasensors, which are biosensors that use aptamers (short DNA or RNA molecules) to specifically bind to target molecules, gold nanoparticles (GNPs) have traditionally been synthesized using citric acid. However, citric acid-capped GNPs are not optimized for constructing aptasensors. In this study, we aimed to develop a more sensitive, selective, and efficient antioxidant-capped GNP (A-GNP) probe for the colorimetric detection of kanamycin. We assessed the performance of A-GNPs synthesized with polyphenols, multi-carboxylic acids, ascorbic acid, and kojic acid, as both reducing agents and stabilizers. Among the tested antioxidants, only ascorbic acid and gallic acid mediated the formation of A-GNPs at room temperature and these could be optimized to construct aptasensors by functionalizing the A-GNPs with poly(adenine)-tailed DNA aptamers (pA-apt). The colorimetric probe using gallic acid-capped GNPs had a limit of detection for kanamycin of 6.2 nM, which is lower than the 22.0 nM value obtained using citric acid-capped GNPs. Furthermore, this aptasensor showed high selectivity for kanamycin, indicating that the A-GNP/pA-apt probe could be applied as a novel aptasensor for antibiotic detection in real-world contexts.