Donor Dye Research Articles

Strong light-matter coupling for optical switching through the fluorescence and FRET control

Resonant interaction between excitonic transitions of molecules and localized electromagnetic field forms the hybrid polaritonic states. Tuneable microresonators may change the light-matter coupling strength and modulate them from weak to strong and ultra-strong coupling regimes. In this work we have realised strong coupling between the tuneable open-access cavity mode and the excitonic transitions in oligonucleotide-based molecular beacons with their terminus labelled with a pair of organic dye molecules demonstrating an efficient donor-to-acceptor Förster resonance energy transfer (FRET). We show that the predominant strong coupling of the cavity photon to the exciton transition in the donor dye molecule can lead to such a large an energy shift that the energy transfer from the acceptor exciton reservoir to the mainly donor lower polaritonic state can be achieved, thus yielding the chromophores’ donor–acceptor role reversal or “carnival effect”. The data show the possibility for confined electromagnetic fields to control and mediate polariton-assisted remote energy transfer. Obtained results open the avenues to quantum optical switching and other applications.

Excitation polarization angle-resolved single-laser dual-polarization energy transfer on the cell surface

A quick and robust approach for the simultaneous detection of donor and acceptor anisotropies and FRET efficiency is presented based on changing the angle of polarization of the exciting light in a single-laser dual channel ratiometric detection scheme of FRET in a flow cytometer. The convenience of the method lies in that for the extra assessment of anisotropies it does not necessitates alteration of the detection side of the optics conventionally used in measuring FRET in the steady state. The detection of anisotropies is pushed to the side of excitation where anisotropies are enabled by just a few sequential measurements at different polarization angles of the exciting light. The power of the method is illustrated by comparing results on the homo-associations and inter-subunit FRET on the MHCI receptor on the surface of Kit-225K6 T cells obtained with the angle-resolved approach to those obtained by the dual-T format approach as a validation. In flow conditions, but not in imaging microscopy, a minor drawback of this method is that due to the sequential nature of anisotropy detection, the mutual cell-by-cell correlations of anisotropies with each other and with FRET are lost. The merit of the approach is that besides the degree of molecular associations probed by the FRET efficiency, information can also be gained on the rotational dynamics and extent of homo-FRET prevailing in the the donor and acceptor dye systems during the hetero-FRET process, and as a consequence, orientation factor for FRET can also be estimated. FRET efficiencies at the different polarization angles are shifted depending on the donor and acceptor anisotropy, enabling quantitation of anisotropy changes by FRET efficiency. Attention is called for polarization biases when using even depolarized excitation and detecting not concerning with fluorescence polarization. When established in polarization contrast microscopy, the approach might be applied for also controlling FRET.A new formula for the determination of the sensitivity calibration factor for FRET α (or Get) has also been deduced based on the donor and acceptor anisotropies.

Film Formation of Waterborne 2K Polyurethanes: Effect of Polyols Containing Different Carboxylic Acid Content

While the interaction of NCO with carboxylic acids has been documented, a comprehensive knowledge of its effect on the film formation in a two-component waterborne polyurethane (2K-WPU) system is lacking. In this work, we synthesized a series of carboxyl-functional acrylic polyols (Mn ≈ 5000 g/mol, Đ ≈ 2.7, Tg ≈ 15 °C) of uniform diameter (120 nm) with varying amounts of methacrylic acid introduced into the latex. For 2K-WPU dispersions with a molar NCO/OH ratio of 1.3:1, we monitored particle size by dynamic light scattering and NCO consumption by FTIR. In the dispersion, we found that the particle size remained nearly constant, and the NCO was almost completely consumed after 2 days. Incorporating COOH in the polyol latex accelerated the consumption of NCO. We synthesized polyol samples labeled with donor and acceptor dyes for fluorescence resonance energy transfer (FRET) studies of polymer diffusion and molecular mixing. In films formed from the polyol latex in the absence of hmPIC, the COOH content of the polyols had no significant effect on the rate or extent of polymer diffusion. In contrast, in films formed from the 2K-WPU dispersions with a stoichiometric NCO/OH ratio (1.3:1), the extent of ET rapidly increased to the maximum value, showing that the full extent of molecular mixing of the two components can be accomplished in films. Thus, the hmPIC acts as a reactive plasticizer. In parallel experiments in which the hmPIC was labeled with the donor dye, we found evidence for partial mixing of the PIC and polyol in the dispersed state. We also showed that the rate of mixing of the hmPIC and the polyol in the films cast from these dispersions was accelerated by −COOH groups in the polyol.

Transition Metal Ion FRET in the Gas Phase: A 10-40 Å Range Molecular Ruler for Mass-Selected Biomolecular Ions.

Structural studies of mass-selected biomolecules in the gas phase can reveal their intrinsic properties and provide useful benchmarks for biomolecular modeling. Here, we report the first evidence of transition metal ion FRET (tmFRET) in the gas phase and its application to measure short (10-40 Å) biomolecular backbone distances. The measured FRET efficiencies in rhodamine dye (donor) labeled helical peptides complexed with Cu2+ ions (acceptor) decreased with increasing donor - acceptor distances, confirming the occurrence of tmFRET. The distances estimated for similar peptide sequences from the FRET efficiencies were consistently longer in the gas phase compared to those reported in solution, indicating an expanded structure and a possible loss of helicity.

Iron Redox Shuttles with Wide Optical Gap Dyes for High-Voltage Dye-Sensitized Solar Cells.

A series of iron polypyridyl redox shuttles were synthesized in the 2+ and 3+ oxidation states and paired with a series of wide optical gap organic dyes with weak aryl ether electron-donating groups. High voltage dye-sensitized solar cell (HV-DSC) devices were obtained through controlling the redox shuttle energetics and dye donor structure. The use of aryl ether donor groups, in place of commonly used aryl amines, allowed for the lowering of the dye ground-state oxidation potential which enabled challenging to oxidize redox shuttles based on Fe2+ polypyridyl structures to be used in functional devices. By carefully designing a dye series that varies the number of alkyl chains for TiO2 surface protection, the recombination of electrons in TiO2 to the oxidized redox shuttle could be controlled, leading to HV-DSC devices of up to 1.4 V.

An Efficient Narrowband Near-Infrared at 1040nm Organic Photodetector Realized by Intermolecular Charge Transfer Mediated Coupling Based on a Squaraine Dye.

A highly sensitive short-wave infrared (SWIR, λ> 1000 nm) organic photodiode (OPD) is described based on a well-organized nanocrystalline bulk-heterojunction (BHJ) active layer composed of a dicyanovinyl-functionalized squaraine dye (SQ-H) donor material in combination with PC61 BM. Through thermal annealing, dipolar SQ-H chromophores self-assemble in a nanoscale structure with intermolecular charge transfer mediated coupling, resulting in a redshifted and narrow absorption band at 1040 nm as well as enhanced charge carrier mobility. The optimized OPD exhibits an external quantum efficiency (EQE) of 12.3% and a full-width at half-maximum of only 85 nm (815 cm-1 ) at 1050 nm under 0 V, which is the first efficient SWIR OPD based on J-type aggregates. Photoplethysmography application for heart-rate monitoring is successfully demonstrated on flexible substrates without applying reverse bias, indicating the potential of OPDs based on short-range coupled dye aggregates for low-power operating wearable applications.

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

Donor group influence on dye-sensitized solar cell device performances: Balancing dye loading and donor size

Four high photocurrent near-infrared (NIR)-absorbing metal-free organic sensitizers (ND1, ND2, ND3, and AP25) with varying nitrogen-based donor groups are examined for use in dye-sensitized solar cell (DSC) devices. One of the highest photocurrent generating organic dyes based on a triarylamine donor reported in the literature (AP25 at 19 mA/cm2) is compared to dyes varying the donor group with constant intramolecular charge transfer π-bridge-acceptor systems. Specific popular donor groups include the bulky Hagfeldt donor (ND1), a carbazole donor (ND2), and an indoline donor (ND3) which varies a large range of sizes (maximum width varies between 8 Å and 26 Å). Computational analysis, dye energetics, absorption profiles (in solution and on TiO2), device incident photon-to-current conversion efficiencies (IPCEs), electrochemical impedance spectroscopy, small modulated photovoltage transient spectroscopy, and device current-voltage curves are used to probe dye behavior based on donor group selection. Balancing donor size and dye loadings was found to be critical for higher performances with the DSC dyes accessing low energy photons near 900 nm.

Density functional theory design of double donor dyes and electron transfer on dye/TiO2(101) composite systems for dye-sensitized solar cells.

In this work, we designed a series of double donor organic dyes, named ME101–ME106, based on experimentally synthesized dye WD8, and further investigated their electronic structure, the stability of the dye/TiO2 (101) systems, density of states (DOS) and absorption spectra using density functional theory (DFT) and time-dependent DFT (TDDFT). The molar extinction coefficients of all designed dyes are higher than WD8. It's fascinating that ME106 exhibits a smallest energy gap and 75 nm redshifts compared to WD8. The results of calculations reveal that ME101–ME106/TiO2(101) surfaces are more stable than WD8, double donor dyes have sufficient electron injection driving force and have very strong transfer electron ability. It is expected that the design of double donors can provide a new understanding and guidance for the investigation of high efficiency dye-sensitized devices.

FRET-Based Method for Direct, Real-Time Measurement of DNA Methyltransferase Activity.

DNA methyltransferase activity is associated with a host of diseases, including cancers, where global hypomethylation of the genome, as well as marked changes in local DNA methylation patterns, can be both diagnostic and prognostic for the disease. Despite this, we currently lack a method for directly measuring the activity of the DNA methyltransferases, which would support the development of DNA methyltransferase-targeted therapies. Here, we demonstrate an assay for the direct measurement of methyltransferase activity, in real time. We employ a fluorescent methyltransferase cofactor analogue, which when bound by the enzyme to a labeled target DNA sequence results in fluorescence resonance energy transfer (FRET) between the donor dye (DNA) and the acceptor dye (cofactor). We demonstrate that the method can be used to monitor the activity of DNA MTases in real time and can be applied to screen inhibitors of the DNA methyltransferases. We show this in both bulk phase and single molecule imaging experiments, highlighting the potential application of the assay in screening and biophysical studies of methyltransferase function.

Monitoring Polymer Diffusion in a Waterborne 2K Polyurethane Formulation Based on an Acrylic Polyol Latex

We report experiments based upon fluorescence resonance energy transfer (FRET) measurements designed to examine mixing at the molecular level of the components of a waterborne 2K polyurethane (WB2KPU) formulation. The system consists of an acrylic polyol latex (Mₙ = 4200 g/mol, D = 2, Tg ≈ 15 °C) with a uniform hydrodynamic diameter (dₕ) ≈ 120 nm plus a water-dispersible polyisocyanate (hmPIC, Basonat HW1000 from BASF). We prepared components labeled with phenanthrene (Phen) as the donor dye or with a dimethylaminobenzophenone (Nben) as the acceptor dye. Dynamic light scattering was used to monitor the size and size distribution of the components in the dispersed phase in solution. This signal was dominated by the polyol nanoparticles, which were much larger than the tiny droplets formed by the hmPIC in water. Experiments were carried out at a mole ratio of NCO/polyol-OH of 1.3. We found that the particle size and narrow size distribution remained unchanged up to 22 h after mixing the polyol with the PIC. FRET experiments were carried out on samples in the dispersed state as well as on films formed from these dispersions. Films formed from a 1:1 mixture of (polyol-Phen + polyol-Nben) showed relatively little energy transfer (ΦET = 0.19) even after several hours aging at ambient temperature, indicating that little polymer diffusion occurred in these low-molecular-weight latex films. In contrast, films formed from mixtures of (polyol-Phen + polyol-Nben + hmPIC) showed more extensive energy transfer (ET) (ΦET = 0.51), indicating essentially complete mixing at the molecular level of the polymer molecules in the presence of hmPIC. The key conclusion is that hmPIC is a reactive plasticizer that promotes diffusion in this system on a much faster scale than the cross-linking reaction. This result is confirmed by experiments that examined mixtures of (hmPIC-Phen + polyol-Nben), which also showed essentially molecular scale mixing between these two different components. In this later system, aging at room temperature led to a small decrease in ΦET over time that was more prominent for films aged at high humidity (75%) than at lower humidity (45%). This result suggests that hydrolysis of NCO groups in the film, leading to polyurea formation, promotes local phase separation accompanied by a net increase in the average separation of Phen and Nben groups in the film.

Sensitive quantitative image analysis of bisulfite based on near-infrared upconversion luminescence total internal reflection platform

Bisulfite (HSO3−), serves as an important additive in food industry, is one of the most widely distributed environmental pollutants. Herein, a fast and efficient quantitative image analysis method for the determination of HSO3− has been developed. The method builds a luminescence energy transfer (LET) system utilized upconversion nanoparticles (UCNPs) as an energy donor and cyanine dye molecules as an energy acceptor. The upconversion luminescence is quenched a lot on the addition of dye molecules and gets recovered well with the addition of HSO3−. All the phenomena can be recorded via traditional luminescence spectrometer and near-infrared upconversion luminescence total internal reflection platform. The quantitative image analysis performed on the near-infrared upconversion luminescence total internal reflection platform can significantly reduce sample consumption (10 μL) as well as make a quick and efficient analysis (0.1 s) with a large amout of data become easy. Meanwhile, it shows a wider linear range (1–120 μM), lower detection limit (0.070 μM) and higher detection speed than that of the classical luminescence spectrometer.

Full Visible Spectrum Panchromatic Triple Donor Dye for Dye-Sensitized Solar Cells

An organic dye with three electron donating groups is studied that has broad full visible spectrum panchromatic absorption in solution. The donor groups introduce six significant optical transition...

Smartphone-assisted detection of nucleic acids by light-harvesting FRET-based nanoprobe

Point-of-care assays for optical detection of biomolecular markers attract growing attention, because of their capacity to provide rapid and inexpensive diagnostics of cancer and infectious diseases. Here, we designed a nanoprobe compatible with a smartphone RGB camera for detection of nucleic acids. It is based on light-harvesting polymeric nanoparticles (NPs) encapsulating green fluorescent donor dyes that undergo efficient Förster Resonance Energy Transfer (FRET) to red fluorescent acceptor hybridized at the particle surface. Green-emitting NPs are based on rhodamine 110 and 6G dyes paired with bulky hydrophobic counterions, which prevent dye self-quenching and ensure efficient energy transfer. Their surface is functionalized with a capture DNA sequence for cancer marker survivin, hybridized with a short oligonucleotide bearing FRET acceptor ATTO647N. Obtained 40-nm poly(methyl methacrylate)-based NP probe, encapsulating octadecyl rhodamine 6G dyes with tetrakis(perfluoro-tert-butoxy)aluminate counterions (~6000 dyes per NP), and bearing 65 acceptors, shows efficient FRET with >20% quantum yield and a signal amplification (antenna effect) of 25. It exhibits ratiometric response to the target DNA by FRET acceptor displacement and enables DNA detection in solution by fluorescence spectroscopy (limit of detection 3 pM) and on surfaces at the single-particle level using two-color fluorescence microscopy. Using a smartphone RGB camera, the nanoprobe response can be readily detected at 10 pM target in true color and in red-to-green ratio images. Thus, our FRET-based nanoparticle biosensor enables detection of nucleic acid targets using a smartphone coupled to an appropriate optical setup, opening the way to simple and inexpensive point-of-care assays.

3D PRINTED HYDROGEL GLUCOSE SENSOR ON ARGON PLASMA ACTIVATED POLYSTYRENE

This study presents a proof of principle concept for a two-dimensional bioprinted glucose sensor on Petri dishes that allows for glucose measurements in cell culture medium. To improve bioink adhesion, the polystyrene surfaces of standard Petri dishes are activated with argon plasma, which increases roughness and hydrophilicity. The bioink containing the sensor chemistry—namely fluorescently labeled ConA/Dextran embedded in alginate microbeads—was printed on the activated Petri dishes with an extrusion-based bioprinter. The printed sensor showed good stability and adhesive properties on polystyrene. The glucose concentration was examined using a standard fluorescence microscope with filters adapted to the emission wavelength of the donor and reference dyes. The printed glucose sensor showed high sensitivity and good linearity in a physiologically relevant range of glucose concentrations.

Reduction in lasing threshold of hollow-core microstructured optical fiber optofluidic laser based on fluorescence resonant energy transfer

Abstract We demonstrate an optofluidic microcavity laser based on a hollow-core microstructured optical fiber (HCMOF), which uses the hexagonal silica membrane embedded in the HCMOF as resonator. Fluorescence resonant energy transfer (FRET) effect is introduced into the laser successfully when mixed anthocyanin dye solution is used as gain medium. The threshold of the laser is systematically investigated for several concentration proportions of donor dye to acceptor dye. The results prove that the FRET-based laser shows a considerable reduction in lasing threshold from 595 nJ/mm2 to 113 nJ/mm2. The effect of FRET on lasing threshold makes this HCMOF-based optofluidic microcavity laser to be a promising candidate for biochemical sensing applications.

Probing DNA Dynamics: Stacking‐Induced Fluorescence Increase (SIFI) versus FRET

AbstractStacking‐induced fluorescence increase (SIFI) was introduced recently as a method to probe DNA structure and dynamics using only a single fluorescent label. Here we show that the same DNA hairpin dynamics can be recovered, at the single‐molecule level, using either SIFI (with Cy3 as the label) or FRET (with Cy3 as donor and Cy5 as acceptor). We also measured FRET using a donor that cannot undergo SIFI, Cy3B, in the presence and absence of a molecular crowding agent (PEG). Although crowding increases hairpin hybridisation to the same extent with either Cy3 or Cy3B as the donor, the absolute rates are affected by the choice of donor dye. This work shows that SIFI can be used to measure single‐molecule dynamics, which could offer advantages over FRET in some cases. It also illustrates how local dye interactions can influence biomolecular dynamics, which should be considered when designing experiments.

Novel fluorochrome development enables 34-color high-content flow cytometry

Abstract Flow cytometry is an essential technology to identify and quantify cell populations. Here we examined the development of new fluorochromes that could enhance flow cytometry’s capability. The latest spectral flow cytometers have 3 excitation lasers (405nm, 488nm, and 640nm) and incorporate the Avalanche Diodes Photodetector technology, which demonstrates significant improvement in sensitivity for the fluorescent emission signal longer than 800nm. However, there is no commercially available fluorochrome which could be excited by the above lasers and has peak emission signal beyond 800nm. To address the gap in technology, here we engineered 6 new fluorochromes: PE-750, PE-810, PE-830 for blue laser and APC-750, APC-810, APC-830 for red laser. These were created by covalently linking a protein donor dye with an organic small molecule acceptor dye. Then, the fluorochromes were conjugated with antibodies using Click chemistry, which is a simple, robust reaction with high-yield and high-reaction sensitivity. Also, we demonstrated long-term stability at −20°C with protein stabilizing cocktails. Most importantly, in order to show the utility of these novel fluorochromes, we created a 34-color flow cytometry panel to measure broad human immune function with high sensitivity on a 3-laser Aurora. The additional UV laser upgrade will increase the instrument capacity to more than 40 color. This panel will be applied to identify the expression patterns of many different receptors involved in trafficking on multiple different cell types from dissociated tumors and blood samples. In conclusion, this high-content flow cytometry panel will improve analysis and diagnosis in Immuno-oncology and facilitate innovation in biomarker discovery.

Excimer-FRET Cascade in Dual DNA Probes: Open Access to Large Stokes Shift, Enhanced Acceptor Light up, and Robust RNA Sensing.

The efficacy of fluorescent hybridization assays is often limited by the low signal-to-background ratio of the probes that can be partially overcome by sophisticated signal amplification methods. Deep understanding of the mechanisms of fluorescence quenching and energy transfer in complex DNA probes and the choice of optimal donor/acceptor pairs along with rational design can significantly enhance the performance of DNA probes. Here, we proposed and studied novel Förster resonance energy transfer (FRET) dual DNA probes with the excimer-forming pyrene pair as a donor and sulfo-Cy3 dye as an acceptor, which demonstrated remarkable 75-fold enhancement of sulfo-Cy3 fluorescence upon target capturing. Stokes shift up to 220 nm minimizes fluorescence crosstalk. Time-correlated single-photon counting revealed two excited states of pyrene excimer wherein only one is directly involved in the resonance energy transfer to sulfo-Cy3. Optimized DNA probes demonstrated high sensitivity with excellent signal-to-background ratio, which were applied for visualization of 18S rRNA by fluorescent in situ hybridization in HEK-293T cells.

Unsymmetrical Small Molecules for Broad-Band Photoresponse and Efficient Charge Transport in Organic Phototransistors.

Organic photosensitizers have been investigated as effective light-sensing elements that can promote strong absorption with high field-effect mobility in organic phototransistors (OPTs). In this study, a novel organic photosensitizer is synthesized to demonstrate broad-band photoresponse with enhanced electrical performance. An unsymmetrical small molecule of a solubilizing donor (Dsol)-acceptor (A)-dye donor (Ddye) type connected with a twisted conjugation system is designed for broad-band detection (ranging from 250 to 700 nm). This molecule has high solubility, thereby facilitating the formation of uniformly dispersed nanoparticles in an insulating polymer matrix, which is deposited on top of OPT semiconductors by a simple solution process. The broad-band photodetection shown by the organic photosensitizer is realized with improved mobility close to an order of magnitude and high on/off current ratio (∼105) of the organic semiconductor. Furthermore, p-type charge transport behavior in the channel of the OPT is enhanced through the intrinsic electron-accepting ability of the organic photosensitizer caused by the unique molecular configuration. These structural properties of organic photosensitizers contribute to an improvement in broad-band photosensing systems with new optoelectronic properties and functionalities.