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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.

Sapsford K.E.,U.S. Food and Drug Administration | Granek J.,U.S. Food and Drug Administration | Deschamps J.R.,Center for Bio Molecular Science and Engineering Code 6900 | Boeneman K.,Center for Bio Molecular Science and Engineering Code 6900 | And 5 more authors.
ACS Nano | Year: 2011

Botulinum neurotoxins (BoNTs) are extremely potent bacterial toxins that contaminate food supplies along with having a high potential for exploitation as bioterrorism agents. There is a continuing need to rapidly and sensitively detect exposure to these toxins and to verify their active state, as the latter directly affects diagnosis and helps provide effective treatments. We investigate the use of semiconductor quantum dot (QD)-peptide Förster resonance energy transfer (FRET) assemblies to monitor the activity of the BoNT serotype A light chain protease (LcA). A modular LcA peptide substrate was designed and optimized to contain a central LcA recognition/cleavage region, a unique residue to allow labeling with a Cy3 acceptor dye, an extended linker-spacer sequence, and a terminal oligohistidine that allows for final ratiometric peptide-QD-self-assembly. A number of different QD materials displaying charged or PEGylated surface-coatings were evaluated for their ability to self-assemble dye-labeled LcA peptide substrates by monitoring FRET interactions. Proteolytic assays were performed utilizing either a direct peptide-on-QD format or alternatively an indirect pre-exposure of peptide to LcA prior to QD assembly. Variable activities were obtained depending on QD materials and formats used with the most sensitive pre-exposure assay result demonstrating a 350 pM LcA limit of detection. Modeling the various QD-peptide sensor constructs provided insight into how the resulting assembly architecture influenced LcA recognition interactions and subsequent activity. These results also highlight the unique roles that both peptide design and QD features, especially surface-capping agents, contribute to overall sensor activity. © 2011 American Chemical Society.

Nagy A.,U.S. Food and Drug Administration | Gemmill K.B.,Center for Bio Molecular Science and Engineering Code 6900 | Delehanty J.B.,Center for Bio Molecular Science and Engineering Code 6900 | Medintz I.L.,Center for Bio Molecular Science and Engineering Code 6900 | Sapsford K.E.,U.S. Food and Drug Administration
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2014

Quantum dot (QD) nanomaterials have a number of electro-optical properties that make them ideal for biosensing applications. QDs combined with peptides have been used for both targeting and sensing applications, however this review will focus specifically on peptide-functionalized QD biosensors, whose signal transduction occurs through active modulation of the QD photoluminescent properties.

Ding S.,Iowa State University | Cargill A.A.,Iowa State University | Das S.R.,Iowa State University | Medintz I.L.,Center for Bio Molecular Science and Engineering Code 6900 | Claussen J.C.,Iowa State University
Sensors (Switzerland) | Year: 2015

Nanocarbon allotropes (NCAs), including zero-dimensional carbon dots (CDs), one-dimensional carbon nanotubes (CNTs) and two-dimensional graphene, exhibit exceptional material properties, such as unique electrical/thermal conductivity, biocompatibility and high quenching efficiency, that make them well suited for both electrical/electrochemical and optical sensors/biosensors alike. In particular, these material properties have been exploited to significantly enhance the transduction of biorecognition events in fluorescence-based biosensing involving Förster resonant energy transfer (FRET). This review analyzes current advances in sensors and biosensors that utilize graphene, CNTs or CDs as the platform in optical sensors and biosensors. Widely utilized synthesis/fabrication techniques, intrinsic material properties and current research examples of such nanocarbon, FRET-based sensors/biosensors are illustrated. The future outlook and challenges for the research field are also detailed. © 2015 by the authors; licensee MDPI, Basel, Switzerland.

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.

Diaz S.A.,Center for Bio Molecular Science and Engineering Code 6900 | Buckhout-White S.,Center for Bio Molecular Science and Engineering Code 6900 | Ancona M.G.,Washington Technology | Spillmann C.M.,Center for Bio Molecular Science and Engineering Code 6900 | And 3 more authors.
Advanced Optical Materials | Year: 2016

Molecular photonic wires (MPWs) precisely position dyes using structural DNA methodologies where they exploit Förster resonance energy transfer (FRET) to direct photonic energy over nm distances with potential applications in light harvesting, biosensing, and molecular electronics. Although versatile, the number of donor-acceptor dye pairs available and the downhill nature of FRET combine to limit the size and efficiency of current MPWs. HomoFRET between identical dyes should provide zero energy loss but at the cost of random transfer directionality. Here, it has been investigated what HomoFRET has to offer as a means to extend MPWs. Steady-state-, lifetime-, and fluorescence anisotropy measurements along with mathematical models are utilized to experimentally examine various 3-, 4-, and 5-dye MPW constructs containing from 1 to 6 HomoFRET repeat sections. Results show that HomoFRET can be extended up to 6 repeat dyes/5 steps with only a ≈55% energy transfer efficiency decrease while doubling the longest MPW length to a remarkable 30 nm. Critically, analogous constructs lacking the HomoFRET portion are unable to deliver any energy over the same lengths. Even with nondirectionality, the introduction of a repeated-optimized HomoFRET transfer dye is preferable compared to additional less efficient dye species. HomoFRET further provides the benefit of having a higher energy output. Molecular photonic wires (MPWs) position dyes using DNA and utilize Förster resonance energy transfer (FRET) to direct photonic energy. Available donor-acceptor dyes limit the size of current MPWs. HomoFRET between identical dyes should provide zero loss but with random directionality. Here, HomoFRET up to five steps in model constructs has been extended with only ≈50% energy transfer loss while doubling MPW length to 30 nm. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dennis A.M.,Boston University | Delehanty J.B.,Center for Bio Molecular Science and Engineering Code 6900 | Medintz I.L.,Center for Bio Molecular Science and Engineering Code 6900
Journal of Physical Chemistry Letters | Year: 2016

Efforts to create new nanoparticle-biomolecule hybrids for diverse applications including biosensing, theranostics, drug delivery, and even biocomputation continue to grow at an unprecedented rate. As the composite designs become more sophisticated, new and unanticipated physicochemical phenomena are emerging at the nanomaterial-biological interface. These phenomena arise from two interrelated factors, namely, the novel architecture of nanoparticle bioconjugates and the unique physicochemical properties of their interfacial environment. Here we examine how the augmented functionality imparted by such hybrid structures, including accessing concentric energy transfer, enhanced enzymatic activity, and sensitivity to electric fields, is leading to new applications. We discuss some lesser-understood phenomena that arise at the nanoparticle interface, such as the complex and confounding issue of protein corona formation, along with their unexpected benefits. Overall, understanding these complex phenomena will improve the design of composite materials while uncovering new opportunities for their application. © 2016 American Chemical Society.

PubMed | Center for Bio Molecular Science and Engineering Code 6900
Type: Journal Article | Journal: The journal of physical chemistry. C, Nanomaterials and interfaces | Year: 2010

We characterized the resonance energy transfer interactions for conjugates consisting of QD donors self-assembled with three distinct fluorescent protein acceptors: two monomeric fluorescent proteins, the dsRed derivative mCherry or yellow fluorescent protein and the multi-chromophore 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 Frster dipole-dipole formalism, with transfer efficiencies that vary with the degree of spectral overlap, 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.

PubMed | Center for Bio Molecular Science and Engineering Code 6900
Type: Journal Article | Journal: Nature materials | Year: 2010

The use of semiconductor quantum dots (QDs) for bioimaging and sensing has progressively matured over the past decade. QDs are highly sensitive to charge-transfer processes, which can alter their optical properties. Here, we demonstrate that QD-dopamine-peptide bioconjugates can function as charge-transfer coupled pH sensors. Dopamine is normally characterized by two intrinsic redox properties: a Nernstian dependence of formal potential on pH and oxidation of hydroquinone to quinone by O(2) at basic pH. We show that the latter quinone can function as an electron acceptor quenching QD photoluminescence in a manner that depends directly on pH. We characterize the pH-dependent QD quenching using both electrochemistry and spectroscopy. QD-dopamine conjugates were also used as pH sensors that measured changes in cytoplasmic pH as cells underwent drug-induced alkalosis. A detailed mechanism describing the QD quenching processes that is consistent with dopamines inherent redox chemistry is presented.

PubMed | Center for Bio Molecular Science and Engineering Code 6900
Type: Evaluation Studies | Journal: Analytical and bioanalytical chemistry | Year: 2013

Cell-penetrating peptides (CPPs) have rapidly become a mainstay technology for facilitating the delivery of a wide variety of nanomaterials to cells and tissues. Currently, the library of CPPs to choose from is still limited, with the HIV TAT-derived motif still being the most used. Among the many materials routinely delivered by CPPs, nanoparticles are of particular interest for a plethora of labeling, imaging, sensing, diagnostic, and therapeutic applications. The development of nanoparticle-based technologies for many of these uses will require access to a much larger number of functional peptide motifs that can both facilitate cellular delivery of different types of nanoparticles to cells and be used interchangeably in the presence of other peptides and proteins on the same surface. Here, we evaluate the utility of four peptidyl motifs for their ability to facilitate delivery of luminescent semiconductor quantum dots (QDs) in a model cell culture system. We find that an LAH4 motif, derived from a membrane-inserting antimicrobial peptide, and a chimeric sequence that combines a sweet arrow peptide with a portion originating from the superoxide dismutase enzyme provide effective cellular delivery of QDs. Interestingly, a derivative of the latter sequence lacking just a methyl group was found to be quite inefficient, suggesting that even small changes can have significant functional outcomes. Delivery was effected using 1 h incubation with cells, and fluorescent counterstaining strongly suggests an endosomal uptake process that requires a critical minimum number or ratio of peptides to be displayed on the QD surface. Concomitant cytoviability testing showed that the QD-peptide conjugates are minimally cytotoxic in the model COS-1 cell line tested. Potential applications of these peptides in the context of cellular delivery of nanoparticles and a variety of other (bio)molecules are discussed.

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