Simple and Sensitive Discrimination of Amino Acids with Functionalized Silver Nanoparticles

A chemiluminescence (CL) sensing method for amino acid discrimination based on luminol functionalized silver nanoparticles (LumAgNPs) has been developed. Luminescence emission in the presence of hydrogen peroxide under neutral conditions was characterized in three ways: the time required for the signal to appear (Ta), the time required to reach maximum luminescence (Tp), and CL intensity. These factors were found to change upon interaction of the nanoparticles with various amino acids, leading to distinct response patterns characteristic of each analyte. Seven amino acids (l-cysteine, l-proline, l-phenylalanine, l-arginine, l-threonine, l-glutamic acid, and l-tyrosine) were identified at a concentration of 10 ng/mL. This sensitivity is about 3 orders of magnitude better than that of recently reported methods based on fluorescent sensor arrays using cucurbit[n]uril and comparable to high-performance liquid chromatography. Application to 27 unknown samples gave a 96.3% success rate at the 10 ng/mL level.