Novel dye-embedded core-shell nanoparticles as surface-enhanced Raman scattering tags for immunoassay

An approach to prepare novel glass-coated gold core-shell nanoparticles embedded with Raman active molecules has been developed. This strategy eliminates the need of a coupling agent and enables efficient embedding of most of commercially available Raman active dyes, even those with weak affinity to a gold surface. Our experiments have demonstrated the hypothesis that the glass encapsulation chemistry is based on the reaction between silanol groups hydrolyzed by TEOS and citrate anion groups adsorbed onto the gold nanoparticles leading to the formation of a silica layer through further reaction with silanol groups of other hydrolyzed TEOS. Furthermore, it has been demonstrated the potential of these novel nanoparticls as Raman tags in ultrasensitive immunoassays for human IgG antigen with a detection limit of 4.9 ng/ml. (c) 2006 Published by Elsevier B.V.