Optical nanocluster microchips for human diagnostics

Metal clusters excited by light exhibit high local field enhancement and nanoscale resonant behavior. Absorptive properties of these metal clusters bound to a surface are the basis of various new and highly promising setups to transduce biorecognitive interactions into an optical signal. Multilayered highly resonant systems had been proposed and recently demonstrated employing a metal mirror, a nanometric polymer distance layer, a biomolecule interaction layer and biorecognitively bound metal nano clusters. The optochips clearly exhibit strong reflection minima induced by the resonant behavior of the metal cluster layer. At least one narrow reflection minimum can be shifted to the red or infra red spectral range and therefore far away from spherical gold colloids (< 520 nm) and human plasma absorption. The setup enabled us to replace conventional binding assays (like ELISA) overcoming the various technological limits as there are multiple incubation steps, harmful reagents and spatial resolution. A modified setup (the metal island coated swelling polymer over mirror system) employing an optical thin-layer system consisting of a metal mirror, an active analyte-induced swelling polymer, and a metal cluster (island) film as the topmost layer was used to transduce human plasma ion concentrations.