21 September 2016 Nanoantennas Enable Forbidden Energy Transfer

DNA-based donor-acceptor-pair in nanoantenna gap

NanoVista collaboration between Institut Fresnel and ICFO in NanoLetters Förster resonance energy transfer (FRET) is commonly used as a nanoruler in biochemistry to monitor the short (nanometer) distance between donor and acceptor dyes. Yet FRET is equally sensitive to the mutual dipole orientation, which often complicates the distance analysis in biological samples. In the far field picture FRET is forbidden for perpendicularly oriented donor and acceptor dipoles. Luckily plasmonic nanoantennas do generate strongly inhomogeneous and localized fields. The non-zero near-field components in all directions open new energy transfer routes, which can overcome the limitations from the mutual dipole orientation and enhance the FRET efficiency.

In a collaboration between Institut Fresnel in Marseille, University of Montpellier and ICFO research groups led by ICREA Professors at ICFO Maria Garcia-Parajo and Niek van Hulst, nanoantennas with nanogaps have been optimized to bring about the increase in energy transfer efficiency for a DNA-based FRET system, with nearly perpendicular donor and acceptor dipoles, enabling an energy transfer which is simply forbidden in a homogeneous environment. The approach increases the applicability of single molecule FRET over diffraction-limited approaches, with the additional benefit of higher sensitivity and higher concentration range toward physiological levels.

The work was published in NanoLetters and carried out under the EU FP7 framework project NanoVista - Photonic Antennas for Biology.