Nanofilms and nanoclusters: energy sources driving fluorophores of biochip bound labels.

Nanoclusters and nanofilms have the potential to amplify fluorescence and thus to enhance the signal of labeled biomolecules on biochip surfaces. Fluorescent molecules are bound at a certain distance to a resonant layer of a metal or a semiconductor or both, resulting in enhanced absorption and emission of the fluorophore within the electromagnetic near-field. This property makes the system highly useful for interaction studies, including those of DNA and proteins. Due to the amount of data, derived from various sequencing projects and from Proteomic interaction studies within the next years, microarrays (or biochips) will represent a central technology in every lab facilitating high-throughput screening and being easily interfaced with computer databases. However, most chips suffer from the disadvantage of insufficient signal-to-noise (background) ratio and are thus limited to molecules of medium-to-high abundance. Novel approaches are needed for identification of, e.g., low copy RNAs or regulatory proteins. Here we present a study, using novel surface enhanced chips in the standard glass-slide-formats. Applying surface-enhanced fluorescence (SEF), the chips turned out to be useful for interaction studies, such as DNA hybridization, thereby strongly enhancing the on-chip-signals. Compared to standard glass-slide-DNA chips, both the fluorescent signals as well as signal-to-noise ratio were considerably higher.