Colloidal SERS Substrate for the Ultrasensitive Detection of Biotinylated Antibodies Based on Near-Field Gradient within the Gap of Au Nanoparticle Dimers

Abstract

Surface-enhanced Raman spectroscopy (SERS) has demonstrated to be a powerful technique for the ultrasensitive detection of different types of analytes and particularly biomolecules, with the rational design of SERS substrates being one of the most relevant issues for the development of effective detection protocols. In this work, a colloidal SERS substrate consisting of a pair of Au nanorods linked by the molecular bridge biotin/streptavidin/biotin has been obtained and employed for the detection of picomolar quantities of the biotinylated antibodies gliadin IgG and Ara h1 IgG, which is of great interest in food science. As a consequence of the bioconjugation strategy implemented, the SERS substrate, that is, the Au nanorod dimer, presents the advantage of combining in a single nanostructure the capabilities for both direct and indirect detection of the biotinylated antibodies. Furthermore, the experimental results are supported by detailed electrodynamics simulations which takes into account not only the gradient of the near-field enhancements within the hot spot but also the volume occupied by the respective biomolecules. The SERS substrate presented here could be straightforwardly employed for the ultrasensitive detection of other biotinylated biomolecules.