Imaging Quantum Dots Switched On and Off by Photochromic Fluorescence Resonance Energy Transfer (pcFRET).

ELIZABETH JARES-ERIJMAN; LUCIANA GIORDANO; CARLA C. SPAGNUOLO; KEITH LIDKE; THOMAS M. JOVIN

Arcachon, Francia

Simposio; ISOP'04 International Symposium On Photochromism; 2004

Bioconjugated semiconductor quantum dots (QDs) are finding widespread application as labelling reagents for cells an macromolecules due to their unique properties. Appropriately designed QDs are very photostable and non-toxic, can be excited with one or more photons over a wide spectral range, yet emit in a narrow and programmable spectral range. Quantum dots are typically capped with a polymer bearing specific binding moieties such as (strep)avidin, protein G, biotin or conjugatable chemical groups. We have shown that diheteroarylethenes can be used as acceptors for photochromic Förster Resonance Energy Transfer (pcFRET), a technique we developed to perform quantitative determination of FRET in vivo. The closed form has an absorption band overlapping the emission band of the donor, which can be returned to the open, non-overlapping, form by exposure to visible light. The system can be cycled repeatedly. We have introduced diheteroarylethenes as reversible acceptors for QDs functioning as FRET donors. We synthesized various diheteroarylethenes and prepared their biotin conjugates. Titrations of QD-565 nm-streptavidin conjugate (Quantum Dot Corp.) with the closed form of a suitable acceptor demonstrated an efficient quenching of the QD. Cyclic irradiation with visible-UV light led to modulation of the luminescence of the QD donors via pcFRET. This phenomenon can be exploited for in vivo microscopy.