Elaboration of an Ag°/TiO2 platform for DNA detection by surface enhanced Raman spectroscopy

The promising potential of a new platform for the label-free DNA detection by Surface Enhanced Raman Spectroscopy (SERS) is reported. This platform is composed of silver nanoparticles distributed over the surface of a TiO2 (anatase) film. DNA molecules are immobilized on the platform using a simple grafting procedure. The elaboration and biomodification of the platform involve wet chemistry routes and benefit from specific properties of its components. First, the photocatalytic activity of TiO2 films is used for the photoreduction of Ag salts leading to the Ag° nanoparticle deposition. Second, the grafting and surface distribution of DNA benefit from both the photo-induced hydrophilicity of TiO2 films and the chemical affinity between metallic silver and amine ligands. Despite a broad size distribution of the Ag° nanoparticles which affects the reproducibility of DNA Raman spectra, specific changes of DNA Raman line intensities observed in single strand and hybridized DNA attest that hybridization can reliably be detected and that a spatially addressed DNA detection is possible.