Amplified electrocatalysis at DNA-modified nanowires.

Arrayed gold nanowires are a novel and useful platform for electrochemical DNA detection. Pilot studies testing the use of these templated structures with an electrocatalytic reporter system revealed that very low detection thresholds for target DNA sequences can be obtained. One factor contributing to the heightened sensitivity is the high signal-to-noise ratio achieved with the large electrocatalytic signals observed at DNA-modified nanowires. Here, we explain the improved sensitivity with evidence illustrating that electrocatalysis at DNA-modified nanostructures generates amplified signals that are significantly larger than those observed at bulk gold surfaces. The results presented strongly suggest that the three-dimensional architectures of the nanowires facilitate the electrocatalytic reaction because of enhanced diffusion occurring around these structures. Effects unique to the nanoscale are shown to underlie the utility of nanowires for DNA biosensing.

Synthesis, characterization, and cellular uptake of DNA-binding rose bengal peptidoconjugates.

Peptide conjugates of the xanthene dye rose bengal (RB) are described featuring sequences that promote DNA binding. The complexation of these conjugates with DNA causes efficient quenching of the fluorophore singlet state and suppresses singlet oxygen production. When incubated with human cells, the RB conjugates pass through the cell membrane but are not visualized in the nucleus. This behavior is in stark contrast to that exhibited by structurally analogous conjugates containing the unhalogenated xanthene dye fluorescein. These results highlight the marked sensitivity of cell permeability characteristics to subtle structural differences.