Time filter

Source Type

Herndon, VA, United States

Blanco-Canosa J.B.,Scripps Research Institute | Blanco-Canosa J.B.,Barcelona Institute for Research in Biomedicine | Wu M.,University of British Columbia | Susumu K.,U.S. Navy | And 6 more authors.
Coordination Chemistry Reviews | Year: 2014

The utility of luminescent semiconductor quantum dots (QDs) in biological applications is directly dependent upon their ability to undergo bioconjugation to proteins, peptides, DNA, drugs and indeed all other manner of biomolecules. In this focused review, we provide an overview of the diverse chemistries that are used for these purposes, including a special emphasis on recent progress by our groups toward optimizing or developing new chemistries. We begin by examining the characteristics and activity ideally desired from QD-bioconjugates, along with the linkage chemistries that are most often utilized. The utility of polyhistidine-mediated metal-affinity coordination to QD surfaces or surface functionalizing ligands is then described in detail. This particular conjugation approach is highly desirable due to its functional simplicity and the control it can afford over the final QD-bioassembly. A variety of other modular, chemoselective ligation chemistries that can be applied either directly on the QD or to the biological to facilitate subsequent QD assembly are described, including aniline-catalyzed imine ligation, thiol-exchange, thiol-targeting iodoacetate chemistry, and Cu(I)-catalyzed azide-alkyne cycloaddition. Commercial QD labeling chemistries that incorporate some of these bioconjugation approaches are also highlighted. Due to their continued widespread use, bioconjugation routes that target the QD surface functionalizing and solubilizing ligands are covered, as are improvements in their functional implementation. Selected examples of applications that incorporate QD-bioconjugates assembled using the different chemistries described are included where appropriate, along with discussion of their benefits and liabilities within that application. Finally, a perspective on remaining issues and how this field will evolve is offered. © 2013 Published by Elsevier B.V. Source

Harmon S.R.,Sotera Defense Solutions | McKinney J.D.,U.S. Navy
Optics Express | Year: 2014

We introduce a novel technique for broadband RF disambiguation which exploits a known jitter imparted onto the sampling rate of an optical pulse source in a subsampled analog optical link. Coarse disambiguation to bandwidths equal to the sample rate is achieved using pure tones as example waveforms by comparing the amplitude of the jitterinduced sidebands relative to the measured signal within the fundamental Nyquist band (frep/2). This sampling technique allows for ultra-wideband signal recovery with a single measurement. In a first-of-its-kind photonics demonstration we show reliable disambiguation for signals with center frequencies spanning 1 MHz - 40 GHz. © 2014 Optical Society of America. Source

Sapsford K.E.,U.S. Food and Drug Administration | Algar W.R.,George Mason University | Algar W.R.,University of British Columbia | Berti L.,University of California at Davis | And 6 more authors.
Chemical Reviews | Year: 2013

Bionanotechnology has now become firmly established in its own right as one of the principle and focused subdisciplines within nanotechnology. Bionanotechnology can be defined as a field representing all facets of research at the intersection of biology and nanomaterials (NM) and is generally characterized as having two somewhat opposite functional goals. The interest in using NMs, and especially NPs, as part of biomolecular composites arises from the unique size-dependent physical, optical, electronic, and chemical properties that they can contribute to the resulting conjugate. These may include quantum confined properties as typified by the size-tunable photoluminescence (PL) of nanocrystalline semiconductor quantum dots (QD), the plasmon resonances of gold NPs, the electrical properties of carbon allotrope NMs, and the paramagnetism and catalytic properties available to certain metal alloy and metal oxide NPs. Source

Canedy C.L.,U.S. Navy | Abell J.,U.S. Navy | Merritt C.D.,U.S. Navy | Bewley W.W.,U.S. Navy | And 4 more authors.
Optics Express | Year: 2014

We report a narrow-ridge interband cascade laser emitting at λ ≈3.5 μm that produces up to 592 mW of cw power with a wallplug efficiency of 10.1% and beam quality factor of M2 = 3.7 at T = 25 °C. A pulsed cavity length study of broad-area lasers from the same wafer confirms that the 7-stage structure with thicker separate confinement layers has a reduced internal loss of ≈3 cm-1. More generally, devices from a large number of wafers with similar 7-stage designs and wavelengths spanning 2.95-4.7 μm exhibit consistently higher pulsed external differential quantum efficiencies than earlier state-of-the-art ICLs. © 2014 Optical Society of America. Source

Algar W.R.,Center for Bio Molecular Science and Engineering | Algar W.R.,George Mason University | Wegner D.,CNRS Fundamental Electronics Institute | Huston A.L.,U.S. Navy | And 7 more authors.
Journal of the American Chemical Society | Year: 2012

The unique photophysical properties of semiconductor quantum dot (QD) bioconjugates offer many advantages for active sensing, imaging, and optical diagnostics. In particular, QDs have been widely adopted as either donors or acceptors in Förster resonance energy transfer (FRET)-based assays and biosensors. Here, we expand their utility by demonstrating that QDs can function in a simultaneous role as acceptors and donors within time-gated FRET relays. To achieve this configuration, the QD was used as a central nanoplatform and coassembled with peptides or oligonucleotides that were labeled with either a long lifetime luminescent terbium(III) complex (Tb) or a fluorescent dye, Alexa Fluor 647 (A647). Within the FRET relay, the QD served as a critical intermediary where (1) an excited-state Tb donor transferred energy to the ground-state QD following a suitable microsecond delay and (2) the QD subsequently transferred that energy to an A647 acceptor. A detailed photophysical analysis was undertaken for each step of the FRET relay. The assembly of increasing ratios of Tb/QD was found to linearly increase the magnitude of the FRET-sensitized time-gated QD photoluminescence intensity. Importantly, the Tb was found to sensitize the subsequent QD-A647 donor-acceptor FRET pair without significantly affecting the intrinsic energy transfer efficiency within the second step in the relay. The utility of incorporating QDs into this type of time-gated energy transfer configuration was demonstrated in prototypical bioassays for monitoring protease activity and nucleic acid hybridization; the latter included a dual target format where each orthogonal FRET step transduced a separate binding event. Potential benefits of this time-gated FRET approach include: eliminating background fluorescence, accessing two approximately independent FRET mechanisms in a single QD-bioconjugate, and multiplexed biosensing based on spectrotemporal resolution of QD-FRET without requiring multiple colors of QD. © 2012 American Chemical Society. Source

Discover hidden collaborations