Thioglucose functionalized gold nanoparticles as active substrates for surface enhanced Raman spectroscopy of lectins

Vibrational spectroscopy methods display great potential in the study of biomolecules. The complexity of these molecular systems, though, is often a hindrance for the interpretation of the experimental spectra. Selective techniques should therefore be improved and applied extensively. This article presents surface enhanced Raman spectra of an important model protein, namely, wheat germ agglutinin. To obtain these spectra, a novel substrate for the protein has been developed. The substrate is based on gold nanospheroids, produced by wet synthesis. The nanoparticles are then functionalized by reaction with a solution of β-D-thioglucose to increase the affinity of the agglutinin for the surface. When nanoparticle films are placed in contact with diluted agglutinin solutions, vibrational bands of the protein appear and can be easily discriminated from those of the substrate. The Raman bands of the substrate and of the protein have then been assigned correlatively. On this basis, we conclude that the interaction between the agglutinin and the nanoparticles is selectively detected only when the metal surface is suitably functionalized.