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Comparison of turn-on and ratiometric fluorescent G-quadruplex aptasensor approaches for the detection of ATP
摘要： Two fluorescent aptasensor methods were developed for the detection of ATP in biochemical systems. The first method consisted of a label-free fluorescent Bturn-on^ approach using a guanine-rich ATP aptamer sequence and the DNA-binding agent berberine complex. In the presence of ATP, the ATP preferentially binds with its aptamer and conformationally changes into a G-quadruplex structure. The association of berberine with the G-quadruplex results in the enhancement of the fluorescence signal of the former. The detection limit of ATP was found to be 3.5 μM. Fluorescence, circular dichroism and melting temperature (Tm) experiments were carried out to confirm the binding specificity and structural changes. The second method employs the ratiometric fluorescent approach based on the Forster resonance energy transfer (FRET) for the detection of ATP using berberine along with a quencher (AuNRs, AgNPs) and a fluorophore (red quantum dots (RQDs), carbon dots (CDs)) labeled at 5′ and 3′ termini of the ATP-binding aptamer sequence. Upon addition of ATP and berberine, ATP specifically binds with its aptamer leading to the formation of G-quadruplex, and similarly, berberine also binds to the G-quadruplex. This leads to an enhancement of fluorescence of berberine while that of RQD and CDs were significantly quenched via FRET. The respective detection limits calculated were 3.6 μM and 3.8 μM, indicating these fluorescent aptasensor methods may be used for a wide variety of small molecules.
关键词： Aptasensor,Adenosine-5′-triphosphate,Gold nanorods,Fluorescence,FRET,Berberine
更新于2025-09-23 15:22:29
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A genetically encoded FRET biosensor for visualizing EphA4 activity in different compartments of the plasma membrane
摘要： The EphA4 receptor tyrosine kinase is well known for its pivotal role in development, cancer progression, and neurological disorders. However, how EphA4 kinase activity is regulated in time and space still remains unclear. To visualize EphA4 activity in different membrane microdomains, we developed a sensitive EphA4 biosensor based on F?rster resonance energy transfer (FRET), and targeted it in or outside raft-like microdomains in the plasma membrane. We showed that our biosensor can produce a robust and specific FRET response upon EphA4 activation, both in vitro and in live cells. Interestingly, we observed stronger FRET responses for the non-raft targeting biosensor than for the raft targeting biosensor, suggesting that stronger EphA4 activation may occur in non-raft regions. Further investigations revealed the importance of the actin cytoskeleton in suppressing EphA4 activity in raft-like microdomains. Therefore, our FRET-based EphA4 biosensor could serve as a powerful tool to visualize and investigate EphA4 activation and signaling in specific subcellular compartments of single live cells.
关键词： EphA4,Membrane microdomain,cytoskeleton,FRET biosensor,Live cell imaging
更新于2025-09-23 15:22:29
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Fluorescence Resonance Energy Transfer-Based Photonic Circuits Using Single-Stranded Tile Self-Assembly and DNA Strand Displacement
摘要： Structural DNA nanotechnology has great potential in the fabrication of complicated nanostructures and devices capable of bio-sensing and logic function. A variety of nanostructures with desired shapes have been created in the past few decades. But the application of nanostructures remains to be fully studied. Here, we present a novel biological information processing system constructed on a self-assembled, spatially addressable single-stranded tile (SST) nanostructure as DNA nano-manipulation platform that created by SST self-assembly technology. Utilizing DNA strand displacement technology, the fluorescent dye that is pre-assembled in the nano-manipulation platform is transferred from the original position to the destination, which can achieve photonic logic circuits by FRET signal cascades, including logic AND, OR, and NOT gates. And this transfer process is successfully validated by visual DSD software. The transfer process proposed in this study may provide a novel method to design complicated biological information processing system constructed on a SST nanostructure, and can be further used to develop intelligent delivery of drug molecules in vivo.
关键词： Single-Stranded Tile,Intelligent Delivery,FRET,DNA Nanotechnology,Photonic Logic Circuits,DNA Strand Displacement
更新于2025-09-23 15:22:29
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Enhanced UV emission of TiO <sub/>2</sub> –ZnO nanocomposite films synthesized by simplified sol–gel dip-coating method
摘要： TiO2–ZnO composite film was regarded as a promising candidate for UV emitter devices. For exploring a lower cost and convenient preparation method for highly efficient UV-emission TiO2–ZnO composite film, we used a simplified method in which mixing ZnO sol and TiO2 sol directly to prepare TiO2–ZnO nanocomposite films with a varied atomic ratio of Zn/(Ti + Zn) (TiO2, Z20, Z40, Z60, Z80, ZnO) on glass substrates and discussed its optical properties for the first time in this study. The photoluminescence (PL) spectra indicated that the UV emission of the composite films was greatly enhanced compared with that showed by single-phase TiO2 or ZnO film. In particular, the UV emission intensity of Z60 composite film was enhanced by a factor of 10 compared to that of single-phase ZnO or TiO2. The enhanced PL intensity of the composite films could be attributed to fluorescence resonance energy transfer (FRET).
关键词： TiO2–ZnO Nanocomposite Films,Optical Property,Simplified Sol–Gel Method,FRET
更新于2025-09-23 15:22:29
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Simultaneous fluorometric determination of the DNAs of Salmonella enterica, Listeria monocytogenes and Vibrio parahemolyticus by using an ultrathin metal-organic framework (type Cu-TCPP)
摘要： Ultrathin (<10 nm) nanosheets of a metal-organic framework (MOF-NSs) were prepared in high-yield and scalable production by a surfactant-assisted one-step method. The MOF-NSs possess distinguished affinity for ssDNA but not for dsDNA. This causes the fluorescence of the labeled DNA to be quenched. On binding to the target DNA (shown here for Salmonella enterica, Listeria monocytogenes and Vibrio parahemolyticus), the labeled duplex is released and the fluorescence of the label is restored. The labels Texas Red, Cy3 and FAM were used and give red, red or green fluorescence depending on the kind of pathogen. The detection limits are 28 pM, 35 pM and 15 pM for the gene segments of Salmonella enterica, Listeria monocytogenes and Vibrio parahemolyticus, respectively.
关键词： FRET,Surfactant-assisted synthesis,Two dimensional nanomaterials,Pathogens,Fluorescence sensor,Multiplex detection
更新于2025-09-23 15:22:29
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NIR Emission Nanoparticles Based on FRET Composed of AIE Luminogens and NIR Dyes for Two-photon Fluorescence Imaging
摘要： Near-infrared (NIR) nanoparticles (NPs) based on fluorescence resonance energy transfer (FRET) were prepared by co-encapsulation of a red aggregation-induced emission (AIE) molecule, 2-(4-bromophenyl)-3-(4-(4-(diphenylamino)styryl)phenyl)fumaronitrile (TB), and a commercial NIR fluorescence dye, silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) with an amphiphilic polymer poly(styrene-co-maleic anhydride) (PSMA). The surface of the NPs, PSMA@TB/NIR775, was modified with poly(ethylene glycol) (PEG) to increase the in vivo biocompatibility of the NPs. The PSMA@TB/NIR775 NPs showed a strong NIR (780 nm) narrow emission and excellent two-photon absorption property. Moreover, the NPs exhibited good monodispersity, stability, and low cytotoxicity. Under the excitation of a 1040 nm femtosecond (fs) laser, the emission peaks at 680 nm of TB and 780 nm of NIR775 excited by FRET were obtained. We utilized PSMA@TB/NIR775 NPs as fluorescent contrast agents for two-photon excited NIR microscopic imaging, and good NIR imaging effect of mouse brain vasculature was obtained with the imaging depth of about 150 μm. The FRET strategy by co-encapsulating AIE molecule and NIR dye will be helpful in preparing more narrow emission NIR probes for deep-tissue biological imaging.
关键词： Two-photon imaging,FRET,NIR emission,AIE,Amphiphilic polymer
更新于2025-09-23 15:22:29
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Picomolar Biosensing and Conformational Analysis Using Artificial Bidomain Proteins and Terbiuma??Toa??Quantum Dot F??rster Resonance Energy Transfer
摘要： Although antibodies remain a primary recognition element in all forms of biosensing, functional limitations arising from their size, stability, and structure have motivated the development and production of many different artificial scaffold proteins for biological recognition. However, implementing such artificial binders into functional high-performance biosensors remains a challenging task. Here, we present the design and application of F?rster resonance energy transfer (FRET) nanoprobes comprised of small artificial proteins (αRep bidomains) labeled with a Tb complex (Tb) donor on the C-terminus and a semiconductor quantum dot (QD) acceptor on the N-terminus. Specific binding of one or two protein targets to the αReps induced a conformational change that could be detected by time-resolved Tb-to-QD FRET. These single-probe FRET-switches were used in a separation-free solution-phase assay to quantify different protein targets at subnanomolar concentrations and measure the conformational changes with subnanometer resolution. Probing ligand-receptor binding under physiological conditions at very low concentrations in solution is a special feature of FRET that can be efficiently combined with other structural characterization methods to develop, understand, and optimize artificial biosensors. Our results suggest that the αRep FRET nanoprobes have a strong potential for their application in advanced diagnostics and intracellular live cell imaging of ligand-receptor interactions.
关键词： protein structure,molecular ruler,lanthanides,molecular diagnostics,FRET,binding assay
更新于2025-09-23 15:21:01
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Excitation Transfer in Hybrid Nanostructures of Colloidal Ag2S/TGA Quantum Dots and Indocyanine Green J-Aggregates
摘要： The regularities of the electron excitations exchange in hybrid associates of colloidal Ag2S quantum dots, passivated with thioglycolic acid (Ag2S/TGA QDs) with an average size of 2.2 and 3.7 nm with Indocyanine Green J-aggregates (ICG) were studied in this work by methods of absorption and luminescence spectroscopy. It was shown that IR luminescence sensitization of Ag2S/TGA QDs with an average size of 3.7 nm in the region of 1040 nm is possible due to non-radiative resonance energy transfer from Ag2S/TGA QDs with an average size of 2.2 nm and luminescence peak at 900 nm using ICG J-aggregate as an exciton bridge. The sensitization efficiency is 0.33. This technique provides a transition from the first therapeutic window (NIR-I, 700-950 nm) to the second (NIR-II, 1000-1700 nm). It can allow high to increase the imaging in vivo resolution.
关键词： Non-radiative resonance energy transfer (FRET),Indocyanine green,Hybrid associate,Luminescence properties,Silver sulfide quantum dots,J-aggregates
更新于2025-09-23 15:21:01
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Unimolecular FRET sensors: Simple linker designs and properties
摘要： Protein activation and deactivation is central to a variety of biological mechanisms, including cellular signaling and transport. Unimolecular fluorescent resonance energy transfer (FRET) probes are a class of fusion protein sensors that allow biologists to visualize using an optical microscope whether specific proteins are activated due to the presence nearby of small drug-like signaling molecules, ligands or analytes. Often such probes comprise a donor fluorescent protein attached to a ligand binding domain, a sensor or reporter domain attached to the acceptor fluorescent protein, with these ligand binding and sensor domains connected by a protein linker. Various choices of linker type are possible ranging from highly flexible proteins to hinge-like proteins. It is also possible to select donor and acceptor pairs according to their corresponding F¨oster radius, or even to mutate binding and sensor domains so as to change their binding energy in the activated or inactivated states. The focus of the present work is the exploration through simulation of the impact of such choices on sensor performance.
关键词： FRET Microscopy,Fusion Proteins,Diagnostics,Monte Carlo Simulation,Coarse Graining,Cellular Signaling
更新于2025-09-23 15:21:01
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Introducing New Conjugated Quantum Dots for Photothermal Therapy in Biological Applications
摘要： It is well-known that near-infrared (NIR) light sources are appropriate to ablate benign tumor irreversibly using heat treatment even in deep tissues. The laser light penetration into the skin in these wavelengths is deep (3–5 mm). Applying new stable materials for emitting NIR wavelengths in tumor positions can help cancer treatment. In this paper, synthesis of the conjugated core-multishell Ag/SiO2/Ag and Au/SiO2/Au quantum dots (QDs) with indocyanine green (ICG) is done and their theoretical and experimental absorptions and emissions in the NIR region are investigated. Thus, heat generation (high-resolution medical imaging capabilities) and emission enhancement are explained and described based on the FRET model for the proposed core-multishell QDs and it is shown that Ag/SiO2/Ag with ICG presents 4 times higher emission rate versus ICG alone in NIR region. Also, because of the plasmon hybridization and also resonance light penetration enhancement, the temperature in tissues increases that is useful for photothermal therapy and NIR high-resolution medical imaging for deep tissues. As an alternative application, these nanoparticles with amazing features are used as a heat source in cancer treatment for shallow and deep tissues. Finally, it is shown that Ag/SiO2/Ag QDs are the best solution for this purpose.
关键词： Cancer detection,FRET,Imaging,Quantum dots,Photothermal therapy
更新于2025-09-23 15:21:01