Metal-enhanced PicoGreen fluorescence: Application for double-stranded DNA quantification

PicoGreen (PG) is a fluorescent probe for both double-stranded DNA (dsDNA) detection and quantification based on its ability to form a luminescent complex with dsDNA as compared with the free dye in solution. To expand the sensitivity of PC detection, we have studied the spectral properties of PC, both free and in complex with DNA in solution, when the fluorophore is in proximity to silver nanoparticles. We show that for a broad range of PC concentrations (20 pM-3.5 mu M), it does not form dimers/oligomers and it exists in a monomeric state. On binding to DNA in the absence of silver, PC fluorescence increases approximately 1 100-fold. Deposition of PG/DNA complex onto silver island films (SiFs) increases fluorescence approximately 7-fold due to the metal-enhanced fluorescence (MEF) effect, yielding fluorescence enhancement of 7700-fold as compared with the free dye on glass. In contrast to PC ill complex with DNA, the free dye on SiFs demonstrates a decrease in brightness approximately 5-fold. Therefore, the total enhancement of PC on binding to DNA on silver reaches a value of approximately 38,000 as compared with free PC on SiFs. Consequently. the metal-enhanced detection of PC fluorescence is likely to find important utility for amplified dsDNA quantification. Published by Elsevier Inc.