Label-free DNA detection on the basis of fluorescence resonance energy transfer from oligonucleotide-templated silver nanoclusters to multi-walled carbon nanotubes

In this paper, a new approach for respiratory syncytial virus (RSV) gene sequence detection was described based on the fluorescence resonance energy transfer (FRET) from oligonucleotide-templated silver nanoclusters (DNA–AgNCs) to multi-walled carbon nanotubes (MWCNTs). The specific DNA scaffold combines two fragments: one is enriched with a cytosine sequence fragment (C12) that can result in DNA–AgNCs with a high quantum yield via a chemical reduction method, and the other is the probe fragment (5′-AAA AAT GGG GCA AAT A-3′) which can selectively bind to the gene for RSV. Thus, the as-prepared AgNCs can exhibit enhanced fluorescence when binding to the target DNA sequence and forming a double helix. Because of the introduction of MWCNTs, which can quench the fluorescence of the DNA–AgNCs with an extraordinarily high quenching efficiency (85.8%), a relatively high signal-to-background ratio was achieved. The fluorescence ratio of the DNA–AgNCs was enhanced in a linearly proportional manner to the concentration of the target in the range of 31.25 nM to 2.00 μM with a detection limit (3σ) of 24.00 nM.