Imaging Quantum Dots Switched On and Off by Photochromic Fluorescence Resonance Energy Transfer (pcFRET (original) (raw)
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CdSe−ZnS Quantum Dots as Resonance Energy Transfer Donors in a Model Protein−Protein Binding Assay
Nano Letters, 2001
Specific binding of biotinilated bovine serum albumin (bBSA) and tetramethylrhodamine-labeled streptavidin (SAv−TMR) was observed by conjugating bBSA to CdSe−ZnS core−shell quantum dots (QDs) and observing enhanced TMR fluorescence caused by fluorescence resonance energy transfer (FRET) from the QD donors to the TMR acceptors. Because of the broad absorption spectrum of the QDs, efficient donor excitation could occur at a wavelength that was well resolved from the absorption spectrum of the acceptor, thereby minimizing direct acceptor excitation. Appreciable overlap of the donor emission and acceptor absorption spectra was achieved by size-tuning the QD emission spectrum into resonance with the acceptor absorption spectrum, and cross-talk between the donor and acceptor emission was minimized because of the narrow, symmetrically shaped QD emission spectrum. Evidence for an additional, nonspecific QD−TMR energy transfer mechanism that caused quenching of the QD emission without a corresponding TMR fluorescence enhancement was also observed.
Quantum dots as resonance energy transfer acceptors for monitoring biological interactions
Biophotonics and New Therapy Frontiers, 2006
Due to their extraordinary photophysical properties CdSe/ZnS core/shell nanocrystals (quantum dots) are excellent luminescence dyes for fluorescence resonance energy transfer (FRET) systems. By using a supramolecular lanthanide complex with central terbium cation as energy donor, we show that commercially available biocompatible biotinilated quantum dots are excellent energy acceptors in a time-resolved FRET fluoroimmunoassay (FRET-FIA) using streptavidin-biotin binding as biological recognition process. The efficient energy transfer is demonstrated by quantum dot emission sensitization and a thousandfold increase of the nanocrystal luminescence decay time. A Förster Radius of 90 Å and a picomolar detection limit were achieved in quantum dot borate buffer. Regarding biological applications the influence of bovine serum albumin (BSA) and sodium azide (a frequently used preservative) to the luminescence behaviour of our FRET-system is reported.
Advanced Materials, 2007
Luminescent quantum dots (QDs), with their large absorption cross sections, superior photo-and chemical stability, broad excitation spectra, and narrow emission bandwidths, are excellent alternatives to traditional organic dyes for fluorescence labeling and emerging nanosensing applications. Using various surface-functionalization techniques (including cap exchange and encapsulation methods), QDs can be dispersed in aqueous media. This has naturally led to their use in biological applications, most notably in cellular labeling, and in the development of sensitive assays that can detect small molecules and oligonucleotides in solution. More recently, we and other groups have shown that QDs are unique donor fluorophores for fluorescence resonance energy transfer (FRET) where multiple acceptor dyes can be positioned around the QD to substantially enhance the overall rate of FRET between the QD and proximal dyes. Because of its exquisite sensitivity to changes in donor-acceptor separation distance (with sixth power dependence), FRET has proven to be a powerful method for detecting molecular-scale interactions, such as binding events and changes in protein conformations. FRET-based QD-biomolecule sensing assemblies that are specific for the detection of target molecules including soluble 2,4,6-trinitrotoluene (TNT), DNA, and the activity of various proteolytic enzymes have been demonstrated. Multiphoton fluorescence microscopy is the preferred highresolution imaging method for thick (ca. 1 mm) tissue samples owing to its intrinsic optical sectioning ability and limited out-of-focus photodamage. It also uses far red and near IR excitation (700-1100 nm), which is ideally located in the tissue optical transparency window. However, FRET performance driven by two-photon excitation has been limited by the photophysical properties of organic dyes and fluorescent proteins. In particular, it is often difficult to devise a donoracceptor pair with substantial spectral overlap for high FRET efficiency and nonoverlapping two-photon absorption spectra for limited acceptor direct excitation. A recent report by Larson et al. showed that water-soluble CdSe-ZnS QDs are superior probes for multiphoton fluorescence imaging where typical QD two-photon action cross sections are about one to two orders of magnitude larger than those of organic molecules designed specifically for such applications. In this report, we demonstrate efficient resonance energy transfer between luminescent QDs and proximal dye acceptors driven by a two-photon process using sub-band excitation energy (far red and near IR photoexcitation). The FRET process between QDs and proximal dyes using this format has two unique features: 1) it exploits the very high two-photon action cross sections of QDs compared to those of conventional dyes, which results in a near-zero background contribution from the dye acceptors due to direct excitation, independent of the excitation wavelength; 2) it provides high signal-to-background ratios in FRET imaging of cells and tissue samples by substantially reducing both autofluorescence and direct excitation contributions to the acceptor photoluminescence (PL) signal. These features can considerably simplify data analysis, in particular when signals of both the QD donor and dye acceptor are required to interpret assay results; they can also improve applications such as intracellular FRET sensing and imaging. Our findings also show that the energy transfer resulting from two-photon excitation is entirely con-
Semiconductor QDs have emerged as a novel class of fluorophore with unique photoluminescence properties, in particular, CdSe/ZnS core-shell QDs have been successfully used as biocompatible fluorescence resonance energy transfer donors. Here we report FRET between CdSe/ZnS core-shell QDs (donor) and organic dye fluorescein 27 (F27) (acceptor). The results demonstrate the occurrence of efficient energy transfer in the system and the FRET efficiency is not only influenced by the spectral overlap between the QD donor emission and acceptor absorption, it might depend on QDs surface effect also. Efforts are made to correlate quantitatively spectral dependence of FRET rate with acceptor absorption spectrum, Forster distance, transfer efficiency (E) obtained employing steady-state & time-resolved technique. Figure 3. Steady state Stern-Volmer plots of F0/F vs. concentration of quencher: (A) QD1 and (B) QD2.
FRET from CdSe/ZnS Core-Shell Quantum Dots to Fluorescein 27 Dye
Semiconductor QDs have emerged as a novel class of fluorophore with unique photoluminescence properties, in particular, CdSe/ZnS core-shell QDs have been successfully used as biocompatible fluorescence resonance energy transfer donors. Here we report FRET between CdSe/ZnS core-shell QDs (donor) and organic dye fluorescein 27 (F27) (acceptor). The results demonstrate the occurrence of efficient energy transfer in the system and the FRET efficiency is not only influenced by the spectral overlap between the QD donor emission and acceptor absorption, it might depend on QDs surface effect also. Efforts are made to correlate quantitatively spectral dependence of FRET rate with acceptor absorption spectrum, Forster distance, transfer efficiency (E) obtained employing steady-state & time-resolved technique. M. A. SHIVKUMAR ET AL. 41 Figure 3. Steady state Stern-Volmer plots of F0/F vs. concentration of quencher: (A) QD1 and (B) QD2.
Journal of Fluorescence, 2019
Steady-state absorption and fluorescence spectra, fluorescence decay kinetics of CdSe/ZnS quantum dots (QD) with photochromic diarylethenes (DAE) in toluene have been studied. Two kinds of QDs emitting at 525 and 600 nm were investigated and DAE were selected to ensure good overlap of their photoinduced absorption band with QDs emission spectra. It has been found that photochromic molecules form complexes with QD which results in partial fluorescence quenching. A reversible modulation of QDs emission intensity which correlates with magnitude of transient photoinduced absorption band of the diarylethenes during photochromic transformations has been demonstrated.
We prepared for the first time photoactive colloidal nanospheres consisting of hydrophobic CdSe/ZnS core−shell quantum dots encapsulated in an amphiphilic PMAT polymeric shell containing photochromic diarylethene DAE1 with stoichiometry of ∼6 dye molecules per single quantum dot. The UV-induced photoisomerization of DAE1 molecules results in the partial quenching of the quantum dot emission due to FRET from the quantum dot to DAE1 photoisomer with its absorption band spectrally overlapped with the quantum dot emission. The modulation of the quantum dot emission is reversible under cyclic UV−vis-induced open−closed photoisomerization of DAE1.
Quantum Dot-Based Multiplexed Fluorescence Resonance Energy Transfer
Journal of The American Chemical Society, 2005
We demonstrate the use of luminescent quantum dots (QDs) conjugated to dye-labeled protein acceptors for nonradiative energy transfer in a multiplexed format. Two configurations were explored: (1) a single color QD interacting with multiple distinct acceptors and (2) multiple donor populations interacting with one type of acceptor. In both cases, we showed that simultaneous energy transfer between donors and proximal acceptors can be measured. However, data analysis was simpler for the configuration where multiple QD donors are used in conjunction with one acceptor. Steady-state fluorescence results were corroborated by time-resolved measurements where selective shortening of QD lifetime was measured only for populations that were selectively engaged in nonradiative energy transfer.
Resonance energy transfer between luminescent quantum dots and diverse fluorescent protein acceptors
2009
We characterized the resonance energy-transfer interactions for conjugates consisting of QD donors selfassembled with three distinct fluorescent protein acceptors, two monomeric fluorescent proteins, the dsRed derivative mCherry or yellow fluorescent protein, and the multichromophore b-phycoerythrin light-harvesting complex. Using steady-state and time-resolved fluorescence, we showed that nonradiative transfer of excitation energy in these conjugates can be described within the Förster dipole-dipole formalism, with transfer efficiencies that vary with the degree of spectral overlap, the donor-acceptor separation distance, and the number of acceptors per QD. Comparison between the quenching data and simulation of the conjugate structures indicated that while energy transfer to monomeric proteins was identical to what was measured for QD-dye pairs, interactions with b-phycoerythrin were more complex. For the latter, the overall transfer efficiency results from the cumulative contribution of individual channels between the central QD and the chromophores distributed throughout the protein structure. Due to the biocompatible nature of fluorescent proteins, these QD assemblies may have great potential for use in intracellular imaging and sensing.