Plasmonic Nanotags for On-Dose Authentication of Medical Tablets

Plasmonic nanomaterials have attracted much attention to new anticounterfeiting technology. Since one of current anticounterfeiting problems is fake medical tablets, on-dose authentication of the tablets is strongly required considering tiny area of tablets, biocompatibility, and long shelf life. Previously, Nanotags consisting of self-assemblies of colloidal gold nanoparticles with reporter molecules were proposed, which produce characteristic surface enhanced Raman scattering (SERS) activity. However, long-term stability is rarely discussed for SERS active nanostructures. This study deposits about 10 ng of the Nanotags on a very tiny area of the commercial tablets. Distinguishable SERS signals of reporting molecules are confirmed by 1s irradiation of 785 nm laser over the Nanotags, while Raman spectrum of the ingredients is observed on the tablet without the Nanotags. Rapid authentication of tablets stocked over 8 years is sufficiently carried out. In addition, the Nanotags on the tablets are almost invisible to the eye, in particular, if the tablet surface is uneven or colored. It is considered that the presence of discrete AuNP assemblies allows excellent performances of Nanotag.