Metal-enhanced ethidium bromide emission: Application to dsDNA detection

Ethidium bromide (EB) is a commonly used probe for fluorescence detection and quantification of nucleic acids, since EB forms a highly luminescent complex with dsDNA. Typical detection sensitivity of EB-based assays to dsDNA in solution is about 0.1 μg. With the aim to increase the sensitivity of EB assays we have employed the Metal-Enhanced Fluorescence technology. We show that deposition of the EB/DNA complex solutions onto the silver nanoparticle surface additionally increases the far-field observable fluorescence ≈5-fold, yielding a net fluorescence enhancement factor of ≈180-fold, as compared to the free dye in solution. Subsequently, our approach enables the more sensitive detection of dsDNA.