Detection of NAs based on DNA molecular beacons and/or DNA self-assembly.
(A) Working principle of SPFS: an evanescent field from surface plasmons impinges on a molecular beacon adsorbed at a gold-coated glass prism. In the closed state, the fluorophore is close to the gold surface and fluorescence is quenched, while target hybridization opens the hairpin and switches fluorescence signal on. Reproduced with permission from Ref. . Copyright 2014 American Chemical Society. (B) Schematic behavior of a so called SERS “molecular sentinel”: a DNA hairpin linked to a thin gold film – deposited on packed nanospheres – keeps a Raman label close to the surface when folded. Upon target binding, the label is separated from the surface and the SERS signal is quenched. Reproduced with permission from Ref. . Copyright 2013 American Chemical Society. (C) Combination of HCR and molecular beacon concepts: two hairpins carrying emitting fluorescent tags assemble into chains only in the presence of a target miRNA, while fluorescence is quenched in proximity of the GO surface. Reproduced with permission from Ref. . Copyright 2012 American Chemical Society.