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Synthesis, Anticonvulsant and Binding Interaction Study of Novel Piperamides with Bovine Serum Albumin by Fluorescence Spectroscopy
摘要： A series of piperamides (PA) 8a-j were designed, synthesized and evaluated for their antimicrobial and anticonvulsant activity. Compounds 8a and 8h showed considerable antibacterial activity against B. subtilis with minimum inhibitory concentration (MIC) of 8 and 10 μg/mL, respectively. Compounds 8a and 8h showed advanced anticonvulsant activity as well as lower neurotoxicity than the reference drugs. The interaction between bovine serum albumin (BSA) and PA was investigated using fluorescence quenching and UV-vis absorption spectroscopy. Results showed that PA could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The binding constant and number of binding sites of PA with BSA were obtained. The binding distance was calculated based on Forster non-radiative energy transfer theory.
关键词： Anticonvulsant,bovine serum albumin,fluorescence quenching,piperamide
更新于2025-09-23 15:22:29
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Fluorescence Quenching-Based Mechanism for Determination of Hypochlorite by Coumarin-Derived Sensors
摘要： A fluorescence quenching-based mechanism for the determination of hypochlorite was proposed based on spectroscopic and chromatographic studies on the hypochlorite-sensing potency of three structurally similar and highly fluorescent coumarins. The mode of action was found to rely upon a chlorination of the coumarin-based probes resulting from their reaction with sodium hypochlorite. Importantly, the formation of chlorinated derivatives was accompanied by a linear decrease in the fluorescence intensities of the probes tested. The results obtained suggest the applicability of a coumarin-dependent hypochlorite recognition mechanism for the detection of, as well as for quantitative determination of, hypochlorite species in vitro.
关键词： fluorescence quenching,coumarin,hypochlorite sensing
更新于2025-09-23 15:22:29
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Fluorene – Triazine Conjugated Porous Organic Polymer Framework for Superamplified Sensing of Nitroaromatic Explosives
摘要： A porous organic polymer with fluorene and triazine units (PTF), was synthesised through a simple cost effective method. The material was well characterised by FT-IR, solid state 13C NMR and X-ray photoelectron spectroscopic studies. Absorption spectrum indicated the electronic coupling between the two units in the polymer backbone. Experiments proved high thermal and chemical stability, and porous nature of the material. Luminescence of PTF was quenched, on the addition of ppb level concentration of nitroaromatic compounds. This was attributed to the photo induced electron transfer from the electron rich polymer backbone to the electron deficient nitro aromatic compounds. The observed superamplification effect in the fluorescence quenching was studied extensively by a series of ground state absorption, steady state and time resolved fluorescence experiments. Finally, the superamplified quenching was successfully assigned to static quenching by quenching sphere of action model. High value of static quenching constant of the order of 3.9 × 103 M-1, for picric acid combined with detection limit as low as 89 ppb envisages PTF as an effective chemosensor for nitroaromatic explosives.
关键词： sphere of action model,porous polymer,fluorescence life-time,Stern-Volmer plot,cyanuric chloride,fluorescence quenching
更新于2025-09-23 15:21:21
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Fe3+-selective and sensitive “on-off” fluorescence probe based on the graphitic carbon nitride nanosheets
摘要： An effective and facile “on-off” fluorescence sensing approach for the determination of Fe3+ ion using a large area and relatively uniform size graphitic carbon nitride nanosheets (GCNS) was developed. The prepared GCNS have blue and stable emission, as well as excellent water dispersion, and were applied as an effective fluorescent probe that based on the quenched fluorescence for selective and sensitive detection of Fe3+ ion. Herein, we explain the ambiguous fluorescence quenching mechanism between the GCNS and Fe3+, which mainly springs from the redox potential and empty d orbital of Fe3+. The redox potential and unfilled d orbit of Fe3+ endow it excellent binding force with GCNS, which generates most obvious fluorescence quenching effect with respect to other metal ions. The limit of detection (LOD) for Fe3+ was found to be about 2.06 μM. Therefore, the prepared GCNS has the potential to be used as a fluorescent probe for detection.
关键词： nanosheets,fluorescence detection,g-C3N4,fluorescence quenching mechanism
更新于2025-09-23 15:21:01
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Studies on the Interaction of Cefepime Hydrochloride with Bovine Serum Albumin by Fluorescence, Synchronous Fluorescence, Three-Dimensional Fluorescence and Circular Dichroism
摘要： The investigation on the binding mode between drug and protein is extremely important to understand biopharmaceutics, pharmacokinetics and toxicity of the drug as well as the relationship of structure and function of the protein. It is well proved that biological activity is a function of the chemical structure or structural properties. There is a study on the interaction of cefepime hydrochloride with serum albumin using in-silico molecular docking. But up to date, there is hardly any interaction investigation of cefepime hydrochloride with serum albumin utilizing by fluorescence, synchronous fluorescence, three-dimensional fluorescence and circular dichroism. In this study, the interaction of cefepime hydrochloride with bovine serum albumin in aqueous solution has been investigated by molecular spectroscopy under different pH conditions. The quenching rate constant and binding constant calculated at pH 7.4 indicated the static quenching mechanism and medium binding force. The effect of cefepime hydrochloride on the conformation of bovine serum albumin was analyzed using fluorescence, synchronous fluorescence, three-dimensional fluorescence and circular dichroism. In addition, influence of pH on the binding of cefepime hydrochloride to bovine serum albumin was investigated and the binding ability of the drug to bovine serum albumin deceased under other pH conditions (pH 1.9, 3.5, and 9.0) as compared with that at pH 7.4. As compared with the binding ability of cefepime hydrochloride to native bovine serum albumin that of cefepime hydrochloride to denatured bovine serum albumin deceases dramatically. Furthermore, the effect of metal ions on the binding constant of cefepime hydrochloride with bovine serum albumin was investigated.
关键词： Circular dichroism,Fluorescence quenching,Bovine serum albumin,Three-dimensional fluorescence,Cefepime hydrochloride
更新于2025-09-23 15:21:01
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Optical oxygen sensing by MPA-capped CdTe quantum dots immobilized in mesoporous silica
摘要： A novel nanocomposite luminescent material was prepared by taking advantage of the versatile wet impregnation method for the dispersion of CdTe quantum dots (QDs) into mesoporous silica host matrix and thus providing great interaction between oxygen and QDs, with potential application in an optical oxygen sensor. The optical/spectroscopic properties of the QDs suspended in aqueous media and incorporated in mesoporous silica were evaluated as a function of aging time, temperature variation and oxygen concentration. Luminescence quenching studies were carried out for both QDs suspended in solution and loaded into the silica matrix, in the presence of varying O2 concentration. By Stern-Volmer plot analysis, obtained at different temperatures, it was possible to verify the existence of two types of emission quenching mechanisms for CdTe QDs. After aging for 120 days at room temperature, the QDs in colloidal suspension displayed a small red-shifted emission, which was interpreted as a decreased bandgap energy owing to the increase in the nanocrystal size. In contrast, the emission spectrum of CdTe QDs loaded into the mesoporous SiO2 matrix remained unchanged after aging for the same time at ambient temperature. The presented results will contribute to the discernment of oxygen quenching mechanisms and chemical stability of optical sensors based on CdTe QDs.
关键词： oxygen sensors,mesoporous silica,Quantum Dots,CdTe,wet impregnation,fluorescence quenching
更新于2025-09-23 15:21:01
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Quantitative Understanding of the Ultra-Sensitive and Selective Detection of Dopamine using Graphene Oxide/WS2 Quantum Dot Hybrid
摘要： Herein, we report on the ultra-high sensitive and selective detection of dopamine (DA) at pico-molar level by a low cost sensing platform based on graphene oxide (GO) sheets anchored with tungsten disulfide quantum dots (WS2 QDs). The liquid phase exfoliated WS2 QDs are mostly bilayer type with an average particle size ~2.0 ± 0.3 nm, while the GO sheets are of few-layer thickness. The WS2 QDs are highly luminescent with photoluminescence (PL) quantum yield of ~15% and they exhibit excitation wavelength dependent spectral shift in PL due to the high degree of edge/defect states. In presence of GO, the PL intensity of WS2 QDs partially quenches due to van der Waals interaction and excited-state charge transfer from WS2 to GO. However, in the presence of DA, drastic quenching of PL occurs for WS2/GO hybrid and this enables selective detection of DA as low as 10 pM, which is the lowest among the reported values. We present a new model to quantitatively explain the GO mediated efficient charge transfer and unusual quenching of PL as a function of the DA concentration. Finally, the WS2/GO based sensor is utilized for the detection of DA in the river water and blood serum with a satisfactory recovery, which establishes its practical utility as an efficient environmental/biochemical sensor.
关键词： Fluorescence Quenching,Dopamine,Biosensor,Graphene Oxide,WS2 Quantum Dots
更新于2025-09-23 15:21:01
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Graphene Quantum Dot Oxidation Governs Noncovalent Biopolymer Adsorption
摘要： Graphene quantum dots (GQDs) are an allotrope of carbon with a planar surface amenable to functionalization and nanoscale dimensions that confer photoluminescence. Collectively, these properties render GQDs an advantageous platform for nanobiotechnology applications, including optical biosensing and delivery. Towards this end, noncovalent functionalization offers a route to reversibly modify and preserve the pristine GQD substrate, however, a clear paradigm has yet to be realized. Herein, we demonstrate the feasibility of noncovalent polymer adsorption to GQD surfaces, with a specific focus on single-stranded DNA (ssDNA). We study how GQD oxidation level affects the propensity for polymer adsorption by synthesizing and characterizing four types of GQD substrates ranging ~60-fold in oxidation level, then investigating noncovalent polymer association to these substrates. Adsorption of ssDNA quenches intrinsic GQD fluorescence by 31.5% for low-oxidation GQDs and enables aqueous dispersion of otherwise insoluble no-oxidation GQDs. ssDNA-GQD complexation is confirmed by atomic force microscopy, by inducing ssDNA desorption, and with molecular dynamics simulations. ssDNA is determined to adsorb strongly to no-oxidation GQDs, weakly to low-oxidation GQDs, and not at all for heavily oxidized GQDs. Finally, we reveal the generality of the adsorption platform and assess how the GQD system is tunable by modifying polymer sequence and type.
关键词： molecular dynamics simulations,Graphene quantum dots,oxidation level,ssDNA,adsorption,noncovalent functionalization,fluorescence quenching
更新于2025-09-23 15:21:01
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Ultrasensitive Detection of MicroRNA with a Bismuthene-enabled Fluorescence Quenching Biosensor
摘要： Bismuthene, a monoelemental two-dimensional material, has shown promise in the biomedicine, electronic, and energy fields due to its high carrier mobility and stability at room temperature. However, its use in biosensing applications is restricted due to the undefined quenching mechanism for dye molecules. Herein, we develop a novel ultrathin bismuthene-based sensing platform for microRNA (miRNA)-specific detection that even discriminates single-base mismatches. The detection limit can reach 60 pM. Excitingly, the fluorescence quenching mechanism of bismuthene, ground state weakly fluorescent charge transfer, is determined via femtosecond pump-probe spectroscopy. This finding provides a proof-of-concept platform to i) fundamentally explore the quenching mechanism of bismuthene and ii) sensitively detect miRNA molecules for early cancer.
关键词： biosensor,Bismuthene,microRNA,charge transfer,fluorescence quenching
更新于2025-09-23 15:21:01
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Oligonucleotide Detection and Optical Measurement with Graphene Oxide in the Presence of Bovine Serum Albumin Enabled by Use of Surfactants and Salts
摘要： As graphene oxide-based oligonucleotide biosensors improve, there is a growing need to explore their ability to retain high sensitivity for low target concentrations in the context of biological fluids. Therefore, we innovatively combined assay milieu factors that could influence the key performance parameters of DNA hybridization and graphene oxide (GO) colloid dispersion, verifying their suitability to enhance oligonucleotide–GO interactions and biosensor performance. As a model system, we tested single-strand (ss) DNA detection in a complex solution containing bovine serum albumin (BSA) and salts with surfactants. A fluorescein conjugated 30-mer oligonucleotide ssDNA probe was combined with its complementary cDNA target, together with solute dispersed GO and either non-ionic (Triton X-100 and Tween-20) or anionic sodium dodecyl sulfate (SDS) surfactants. In this context, we compared the effect of divalent Mg2+ or monovalent Na+ salts on GO binding for the quench-based detection of specific target–probe DNA hybridization. GO biosensor strategies for quench-based DNA detection include a “turn on” enhancement of fluorescence upon target–probe interaction versus a “turn off” decreased fluorescence for the GO-bound probe. We found that the sensitive and specific detection of low concentrations of oligonucleotide target was best achieved using a strategy that involved target–probe DNA hybridization in the solution with a subsequent modified “turn-off” GO capture and the quenching of the unhybridized probe. Using carefully formulated assay procedures that prevented GO aggregation, the preferential binding and quenching of the unhybridized probe were both achieved using 0.1% BSA, 0.065% SDS and 6 mM NaCl. This resulted in the sensitive measurement of the specific target–probe complexes remaining in the solution. The fluorescein-conjugated single stranded probe (FAM–ssDNA) exhibited linearity to cDNA hybridization with concentrations in the range of 1–8 nM, with a limit of detection equivalent to 0.1 pmoles of target in 100 μL of assay mix. We highlight a general approach that may be adopted for oligonucleotide target detection within complex solutions.
关键词： graphene oxide,optical DNA sensor,surfactants,fluorescence quenching
更新于2025-09-23 15:21:01