Biosensing based upon molecular confinement in metallic nanocavity arrays

We describe the basis for an affinity biosensor platform in which enhanced fluorescence transduction occurs through the optical excitation of molecules located within metallic nanocavities. These nanocavities are about 200 nm in diameter, are arranged in periodic or random two-dimensional arrays, and are fabricated in 70 nm thick gold films by e-beam lithography using negative e-beam resist. The experimental results show that both periodic and randomly placed metallic nanocavities can be used to enhance the fluorescence output of molecules within the cavities by about a factor of ten. In addition, the platform provides isolation from fluorescence produced by unbound species, making it suitable for real-time detection. Finally, we demonstrate the use of the platform in the real-time detection of 20-base oligonucleotides in solution.