3D ordered gold nanoshell composite array as sensitive SERS nanosensor for detecting l-DOPA and tyrosinase activity

Here we report a novel method for detecting 3,4-dihydroxyphenylalanine (L-DOPA) and tyrosinase (TR) activity based on surface-enhance Raman scattering (SERS) by employing a large-scale versatile three-dimensionally (3D) ordered nanocomposite (SiO2/GNPs) array as a nanosensor. L-DOPA could reduce AuCl4− to Au0 and enlarge the gold nanoparticles (GNPs) that attach on the surface of the SiO2/GNPs array, the preadsorbed GNPs serve as nucleation sites for Au0 to deposit. As the concentration of L-DOPA increases, the surface coverage of resultant Au0 on silica cores increases accordingly until complete gold nanoshells (GNSs) are formed. During the growth procedure, the SERS-activity of the GNSs arrays correlate well with the concentration of L-DOPA, which indicates that this SiO2/GNPs array is a potential nanosensor for detecting L-DOPA. As TR can catalyze the hydroxylation of L-tyrosine to form L-DOPA, this approach can also be employed to analyze the activity of TR, which possesses vast clinical and food industrial importance. Compounds such as cinnamic acid and p-hydroxybenzoic acid can inhibit the TR activity. Thus, the TR-triggered growth of the GNSs array system can also be used to detect the TR inhibited activity of inhibitors.