Imaging switchable semiconductor nanocrystals (quantum dots).

ELIZABETH JARES-ERIJMAN; LUCIANA GIORDANO; CARLA SPAGNUOLO; MARÍA V. MAÑALICH ARANA; GUILLERMO MENENDEZ; KEITH LIDKE; THOMAS M. JOVIN

California, USA

Congreso; 49th Annual Meeting Biophysical Society; 2005

Biophysical Society

Unique characteristics have rendered bioconjugated semiconductor quantum dots (QDs) very attractive as labelling reagents for cell and macromolecules. Emitting in a narrow and programmable spectral range, yet excitable by one of more photons over a wide spectral range, appropriately designed QDs display photostability and non-toxicity. Quantum dots are typically capped with a polymer bearing a variety of 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 Forster 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 non-overlapping form by exposure to visible light. The system can be cycled repeatedly. We have synthesized various diheteroarylethenes and 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 interconvertion between the open and closed forms by irradiation with UV and visible light enabled deactivation and activation of the FRET process, respectively, with a consequent modulation of the quantum dot emission, as seen both in solution and by sequential wide-field imaging. This phenomenon can be exploited for in vivo microscopy and for bionanoelectronics, a field which encompasses the integration of biomolecules with novel nanomaterial components to create optoelectronic devices.