Surface-enhanced Raman scattering of N-acetylneuraminic acid on silver nanoparticle surface

N-Acetylneuraminic acid (sialic acid, Neu5Ac) has recently gained interest as a potential marker for a variety of pathophysiological processes, although no Raman study has been reported for this important biomolecule. In this paper, the vibrational properties of Neu5Ac were studied by means of Raman, surface-enhanced Raman scattering (SERS), and density functional theory calculations. By adsorption of Neu5Ac on silver nanoparticle surface, strongly enhanced Raman intensities are obtained, allowing easy measurement of small amounts of aqueous Neu5Ac (10 μl of a 10^-7 M solution) utilizing low laser power and short exposure time. The mechanism of adsorption of Neu5Ac on the silver surface is discussed on the basis of the experimental and theoretical results. This study demonstrates that SERS can provide an effective tool for development of a label-free, rapid, and sensitive optical platform for identification of Neu5Ac.