Download or read book Fluorescence Resonance Energy Transfer Between a Monolayer of Quantum Dots as Donors Adjacent to a Monolayer of Biorecognition Elements as Acceptors written by Eleonora Petryayeva and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantum Dot fluorescent Protein Pairs as Fluorescence Resonance Energy Transfer Pairs written by Allison Marie Dennis and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluorescence resonance energy transfer (FRET)-based biosensors have been designed to fluorometrically detect everything from proteolytic activity to receptor-ligand interactions and structural changes in proteins. While a wide variety of fluorophores have demonstrated effectiveness in FRET probes, several potential sensor components are particularly notable. Semiconductor quantum dots (QDs) are attractive FRET donors because they are rather bright, exhibit high quantum yields, and their nanoparticulate structure enables the attachment of multiple acceptor molecules. Fluorescent proteins (FPs) are also of particular interest for fluorescent biosensors because design elements necessary for signal transduction, probe assembly, and device delivery and localization for intracellular applications can all be genetically incorporated into the FP polypeptide. : The studies described in this thesis elucidate the important parameters for concerted QD-FP FRET probe design. Experimental results clarify issues of FRET pair selection, probe assembly, and donor-acceptor distance for the multivalent systems. Various analysis approaches are compared and guidelines asserted based on the results. To demonstrate the effectiveness of the QD-FP FRET probe platform, a ratiometric pH sensor is presented. The sensor, which uses the intrinsic pH-sensitivity of the FP mOrange to modulate the FP/QD emission ratio, exhibits a 20-fold change in its ratiometric measurement over a physiologically interesting pH range, making it a prime candidate for intracellular imaging applications.

Download or read book Toward Multiplexed Nucleic Acid Assays and Biosensors Using Immobilized Quantum Dots as Donors in Fluorescence Resonance Energy Transfer FRET written by Walter Russell Algar and published by . This book was released on 2010 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research toward a multiplexed nucleic acid biosensor that uses quantum dots (QDs) as donors in a fluorescence resonance energy transfer (FRET) assay is described. Optical fibers were modified with mixed films composed of different colours of QDs and different oligonucleotide probes that served as scaffolds for the hybridization of the corresponding target nucleic acid sequences. Fluorescent dyes that were suitable as acceptors for each QD donor were associated with hybridization and provided an analytical signal through FRET-sensitized emission. Different detection channels were achieved through the combination of different donors and acceptors: green emitting QDs with Cyanine 3 or Rhodamine Red-X; and red emitting QDs with Alexa Fluor 647. A detection channel that used the direct excitation of Pacific Blue complemented the FRET pairs. One-plex, two-plex, three-plex and four-plex hybridization assays were demonstrated. A sandwich assay format was adopted to avoid target labeling. Detection limits were 1-10 nM (1-12 pmol) and analysis times were 1-4 h. Single nucleotide polymorphisms were discriminated in multiplexed assays, and the potential for reusability was also demonstrated. Non-selective interactions between QDs and oligonucleotides were characterized, and routes toward the optimization of the QD-FRET hybridization assays were identified. A basic model for multiple FRET pathways in a mixed film was also developed. In addition to the advantages of solid-phase assays, the combination of QDs and FRET was advantageous because it permitted multiplexed detection using a single excitation source and a single substrate, in the ensemble, and via ratiometric signals. Spatial registration or sorting methods, imaging or spatial scanning, and single molecule spectroscopy were not required. The research in this thesis is expected to enable new chip-based biosensors in the future, and is an original contribution to both bioanalytical spectroscopy and the bioanalytical applications of nanomaterials.

Download or read book F rster Resonance Energy Transfer from Terbium Complexes to Quantum Dots for Multiplexed Homogeneous Immunoassays and Molecular Rulers written by David Karl Wegner and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Förster resonance energy transfer (FRET) is a non-radiative energy transfer from a donor to an acceptor in close proximity. Due to its extremely sensitive distance dependence in the 1 - 20 nm range, FRET plays an important role in nanobiotechnology. Thereby FRET can be used as signal transduction system but also for the distance estimation between donor and acceptor. The selected FRET acceptors in this work were semiconductor nanocrystals (quantum dots, QDs). This type of luminophore is well known for its superior photophysical properties. Their strong and broad absorption and their bright, narrow-band, and size-tunable photoluminescence (PL) emission make QDs ideally suited for FRET application. Combing QDs as FRET acceptors with luminescent terbium complexes (LTC) as FRET donors offers exceptionally large Förster distances of more than 10 nm. The Förster distance is characteristic of a FRET pair and is the distance at which the FRET efficiency equals 50 %. A large Förster distance is desirable as it offers the detection of biological interactions over large distances. LTC are suitable FRET donors for QDs because they provide long excited-state lifetimes in the millisecond range. This long PL decay time enables time-gated measurements for the suppression of autofluorescence and PL of directly excited QDs, which strongly increases the detection sensitivity. Additionally, the structured PL emission bands of LTCs together with the size-tunable PL emission bands of QDs make this FRET pair ideal for the application in multiplexed diagnostics, which is the measurement of multiple biomarkers in a single sample.The PhD thesis consists of two parts. In the first part the LTC-QD FRET pair was used within homogeneous FRET immunoassays for the detection of the biomarkers prostate specific antigen (TPSA), neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), and epidermal growth factor receptor (EGFR). The immunoassay sensitivity was optimized using different types of antibodies IgG, F(ab')2,F(ab), and for EGFR single heavy chain antibodies, which differ largely in their size. The use of small-volume serum samples and measurements on clinical as well customized fluorescence plate readers result in picomolar detection limits for all measured biomarkers. In addition to these QD-based in vitro diagnostic tests, a detailed study of the different FRET-systems using time-resolved spectroscopy was performed. The investigation revealed the influence of the different antibodies on distance, functionality, and sensitivity of the FRET immunoassays. The study was completed by the measurement of NSE and CEA in a duplexed format and real patient samples were investigated.The second part was to use FRET for nanometric distance measurements as molecular or spectroscopic ruler. Time-resolved FRET measurements enabled the calculation of the distance between donor and acceptor. Therefore two different binding strategies were investigated to establish a close proximity between the LTC-donor to the QD-acceptor, namely biotin-streptavidin recognition and polyhistidine mediated self-assembly. A detailed time-resolved study was performed of QDs with different sizes, shapes, and surface coatings in combination with LTC bound to three different host biomolecules, which also possessed different sizes, shapes, orientations, and binding conditions. The analysis of the multi-exponential decay curves of donor and acceptor allowed to obtain information about the size, shape, and biofunctionality of the investigated QD bioconjugates. The results were in agreement with other structural analysis methods, such as transmission electron microscopy (TEM) or dynamic light scattering (DLS), but with the advantage of a homogeneous measurement with three-dimensional resolution (not possible for TEM), without the inclusion of a hydration shell (drawback for DLS), and at low concentration in the same environment as used for the biological application.

Download or read book Experimental Investigation of Fluorescence Resonance Energy Transfer Using Quantum Dots written by Ee Zhuan Chong and published by . This book was released on 2007 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Towards Multi colour Strategies for the Detection of Nucleic Acid Hybridization Using Quantum Dots as Energy Donors in Fluorescence Resonance Energy Transfer FRET written by Walter Russell Algar and published by . This book was released on 2006 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique optical properties of quantum dots (QDs) are of interest in the development of nucleic acid diagnostics. The potential for a simultaneous two-colour diagnostic scheme for nucleic acids operating on the basis of fluorescence resonance energy transfer (FRET) has been demonstrated. Upon ultraviolet excitation, two-colours of CdSe/ZnS quantum dots with conjugated oligonucleotide probes acted as energy donors yielding FRET-sensitized acceptor emission upon hybridization with fluorophore labeled target oligonucleotides. The use of an intercalating dye to improve signal-to-noise was also demonstrated. The major limitation of the system was the non-specific adsorption of oligonucleotides, which was characterized extensively. Adsorptive interactions were found to affect the conformation of oligonucleotides conjugated to QDs, the kinetics of hybridization with QD-DNA conjugates, and the thermal stability of those hybrids. In addition, it was found that thiol-alkyl-acid capped QDs exhibited pKa correlated ligand-chromism and radiative decay rate-driven changes in quantum yield.

Download or read book Origin of Size dependent Energy Transfer from Photoexcited CdSe Quantum Dots and Fluorescent Dyes to Gold Nanoparticles written by Mariana Kondon and published by . This book was released on 2008 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photoluminescence quenching of CdSe quantum dots (QD) and fluorescent dyes by hexanethiolate Monolayer Protected Clusters (MPCs) with core diameters of 1.1-4.9 nm is described. The CdSe QD investigated had the following core diameters of 2.0, 2.6, 3.4 and 6.9 nm. The florescent dyes used were: Coumarin 440 (CM 440), Fluorescein 548 (F548), Rhodamine 6G (R6G), Pyromethene 597 (PM597) and Lyssamine Dye (LD700). Experimental evidence suggests that the photoluminescence quenching of both CdSe QD and the fluorescent dyes occurs through energy transfer and that the AuMPCs are efficient quenchers in both cases. The larger MPCs are more efficient quenchers. There is a remarkable linear correlation found between the quenching efficiency determined by Stern-Volmer plot and the MPC core volume which suggests that the quenching efficiency is governed by the MPC core-size dependent extinction cross-section that determines the spectral overlap between the emission of the donor (QD and fluorescent dyes) and the absorption of the MPC.

Download or read book Quantum Dots for DNA Biosensing written by Jun-Jie Zhu and published by Springer Science & Business Media. This book was released on 2013-12-04 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a broad introduction to all major aspects of quantum dot properties including fluorescence, electrochemical, photochemical and electroluminescence. Such properties have been produced for applications in biosensing, cell tracking, in vivo animal imaging and so on. It focuses on their special applications in DNA biosensing and provides readers with detailed information on the preparation and functionalization of quantum dots and the fabrication of DNA biosensors, using examples to show how these properties can be used in DNA biosensor design and the advantages of quantum dots in DNA biosensing. Further new emerging quantum dots such as metal nanoclusters and graphene dots and their applications in DNA biosensing have also been included.

Download or read book Investigation of the Separation Dependent Fluorescence Resonant Energy Transfer Between CdSe ZnS Quantum Dots by Near field Scanning Optical Microscopy written by and published by . This book was released on 2009 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Near-field Scanning Optical Microscope (NSOM) is used to study the resonant energy transfer between different size CdSe/ZnS quantum dots (QDs). The NSOM system is used to bring the small QDs which are 6 nm in diameter close to 8 nm diameter QDs which are embed with PMMA on a cover glass. The PMMA is used to prevent the 8 nm QDs from aggregation, which allows us to locate one dot on the cover slide and have the potential to get the interaction of two individual dots. A systematic methodology is used to localize a single QD on the cover glass and align the small and large QDs. Since the ground energy state of the small QDs match the excitation energy level of the large QDs. When the small dots get excited, part of the energy transfers to the large QDs. As the separation between small and large QDs is changed in near-field range (20-50nm), the transition probability is observed, indicating that the FRET level changes as a function of separation between small and large QDs. Possible future improvements are also discussed.

Download or read book Towards The Development Of A Quantum Dot Based Bioprobe For Intracellular Investigations of Nucleic Acid Hybridization Events Using Fluorescence Resonance Energy Transfer written by Lori Lok-Yin Chong and published by . This book was released on 2011 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique spectroscopic properties of quantum dots (QDs) are of interest for application in intracellular studies of gene expression. QDs derivatized with single-stranded probe oligonucleotides were used to detect complementary target sequences via hybridization and fluorescence resonance energy transfer (FRET). As nucleic acid targets are not labeled within cells, a displacement assay for nucleic acid detection featuring QDs as FRET donors was developed. QDs conjugated with oligonucleotide probes and then pre-hybridized with labeled target yielded efficient FRET in vitro. Studies in vitro confirmed that displacement kinetics of pre-hybridized target was a function of the stability of the initial hybridized complex. Displacement was observed as reduction in FRET intensity coupled with regeneration of QD fluorescence. By engineering the sequence of the labeled target, faster displacement was possible. The QD-probe+target system was successfully delivered into cells via transfection. Although QDs with their cargo remained sequestered in endosomal vesicles, fluorescent properties were retained.

Download or read book Template assembly and Spectroscopic Study of Colloidal Quantum Dot Molecules written by Kin Wai Lei and published by . This book was released on 2014 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Block copolymer template-assembly of quantum dots and plasmonic nanostructures is developed to provide a well-controlled platform to study the electronic coupling and Förster resonance energy transfer (FRET) between quantum dots (QDs), as well as the influence of surface plasmons on energy transfer. By fine-tuning the aspect ratio of the geometric features of PS-b-PMMA copolymer template, QDs are assembled into an array of QD clusters within nanoscopic holes on the template using capillary force assembly. Coupled QD clusters, termed quantum dot molecules (QDMs), are assembled in an array to probe the local coupling within QD molecules when the native insulating ligands are exchanged with shorter ligands. From absorption measurement of 1st exciton peak position of PbSe QDMs upon ligand exchange, a larger red-shift is found for QDMs than for a close packed film of PbSe QDs with the same ligand exchange, demonstrating localized electronic coupling of these QD molecules. Template-assembly of nanoparticles is further generalized to uniformly couple QDs clusters with plasmonic nanodisks of noble metals. Using PS nanospheres as reactive ion etch mask, Au nanodisks are fabricated on CdSe/ZnS core shell QD clusters, separated by a tunable space layer of PMMA. This highly controllable surface plasmon-coupled QD system minimizes the uncertainty in interfacial homogeneity, characterized by cross sectional scanning electron microscopy (SEM). Photoluminescence (PL) peak ratio of donor to acceptor emission and donor lifetime measurements show strong evidence of surface plasmon coupled energy transfer between donor-acceptor QDs, which depends on the position of the surface plasmon peaks as well as the separation between plasmonic structure and FRET QD clusters. The result suggests that a larger overlap of surface plasmon peak with the emission peak of acceptor leads to greater decrease in PL lifetime of donor. Donor lifetime decreases dramatically in the presence of both acceptor and surface plasmon compared to just in the presence of surface plasmon. Coupling between plasmonic nanodisks and QD clusters also decreases and results in longer donor lifetime as the thickness of PMMA separation layer increases.

Download or read book Quantum Dots in Bioanalytical Chemistry and Medicine written by Michael Thompson and published by Royal Society of Chemistry. This book was released on 2023-08-25 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum dots are proven powerful probes for fluorescence imaging and have distinct properties that give them unique capabilities. Currently, they are being developed for a range of additional applications including the detection of disease, fluorescent assays for drug discovery, single protein tracking and intracellular reporting. Here, the various types of quantum dots are introduced, with the reader being provided with enough information in the text and the references to encourage a new quantum dot user to get started. Including an overview of the significant advancement in the field and discussing applications, the book emphasises how the properties of quantum dots are employed in bioanalytical chemistry. Closing with a prospectus of the future for quantum dots, any researchers and students in bioanalytical chemistry, medicine and clinical biochemistry will find this title useful supplementary reading.

Download or read book Quantum Dot dye Hybrid Systems for Energy Transfer Applications written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems.rn rnIn the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stöber silica particles with an outer silica shell of thickness 2 - 24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. rnrnNew QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability,

Download or read book Colloidal Quantum Dots for Biomedical Applications written by Kenji Yamamoto and published by SPIE-International Society for Optical Engineering. This book was released on 2006 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of SPIE present the original research papers presented at SPIE conferences and other high-quality conferences in the broad-ranging fields of optics and photonics. These books provide prompt access to the latest innovations in research and technology in their respective fields. Proceedings of SPIE are among the most cited references in patent literature.

Download or read book Use of Luminescent CdSe ZnS Nanocrystal Bioconjugates in Quantum Dot Based Nanosensors written by and published by . This book was released on 2002 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Biomolecules labeled with luminescent colloidal semiconductor quantum dots (QDs) have potential for use in numerous applications, including fluoro-immunoassays and biological imaging. QD labels exhibit size-tunable narrow-band luminescent emission and high resistance to photodegradation. They also exhibit efficient Fo rster energy transfer between neighboring QDs of different sizes and their emission is readily quenched by bound fluorescent dyes. In this paper, we describe preliminary results aimed at defining conditions for the design and preparation of nanoscale QD-bioconjugate sensors based on fluorescence quenching. We envision building sensor assemblies that employ quantum dots linked with dye-labeled biological receptors that utilize donor acceptor energy transfer between QDs and receptors for conducting recognition-based assays. In particular, we report the effects of varying the concentration of energy acceptors bound to nanocrystal surfaces under both soluble and solid phase conditions on quenching phenomena.

Download or read book Surface Plasmon Coupling Effects on the Forster Resonance Energy Transfer Process Between Quantum Dot and Rhodamine 6G written by 陳建瑜 and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Towards the Development of Techniques to Facilitate the Assembly and Characterization of Quantum Dot Gold Nanoparticle Complexes for Resonance Energy Transfer Based Assays written by Uvaraj Uddayasankar and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Resonance energy transfer between quantum dots and gold nanoparticles represents one of the most popular transduction schemes for biosensors using multi-nanoparticle complexes. This thesis investigates the influence of quantum dot positioning, relative to the gold nanoparticle, on the analytical performance of these assays. Stoichiometric assembly of the quantum dot-gold nanoparticle complexes required accurate knowledge of the quantum dot concentration. A technique was developed to quantify the molar concentration of nanoparticles in solution. This technique relied on the quantitative analysis of the statistical distribution of nanoparticle-ligand conjugates that form when nanoparticles are functionalized with small equivalents of ligand. The technique was successfully validated using gold nanoparticles, and was subsequently applied to determine the concentration of the alloy quantum dots. The precise positioning of the quantum dots relative to the gold nanoparticles required monovalent conjugates of the quantum dots. These were prepared using a magnetic bead based technique where positively charged magnetic beads were used to capture and selectively isolate the monovalent quantum dot-DNA conjugates. Successful isolation of monovalent conjugates was confirmed using single molecule fluorescence spectroscopy and the monovalent conjugates were found to retain their activity as determined using quantitative hybridization assays. Optimizing the quantum dot-gold nanoparticle assay required the investigation of two different configurations of nanoparticle arrangement. The first involved arranging quantum dots around a gold nanoparticle core, while the second involved arranging gold nanoparticles around a quantum dot core. The first configuration was found to have optimal analytical performance, as evaluated using quenching efficiencies and influence of inner filter effect. The ability to arrange multiple quantum dots around a single large gold nanoparticle minimized the negative influence of the inner filter effect, while the high quenching efficiency ensured high responses to target hybridization.