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Fluorometric determination of the activity of alkaline phosphatase and its inhibitors based on ascorbic acid-induced aggregation of carbon dots
摘要： The authors describe a fluorometric method for determination of the activity of alkaline phosphatase (ALP) and its inhibitors. Nitrogen and boron co-doped carbon dots (C-dots) with excitation/emission peaks at 490/540 nm act as the fluorescent probe. The C-dots were prepared by hydrothermal carbonization starting from 3-aminophenylboronic acid as the sole precursor. On the basis of the boronic acid-triggered specific reaction with cis-diols, the boronic acid modified C-dots can bind to ascorbic acid that is generated by ALP-catalyzed hydrolysis of ascorbic acid 2-phosphate. This results in particle aggregation and quenching of fluorescence. If the ALP inhibitor Na3VO4 is introduced into the system, the activity of ALP is reduced and the fluorescence of C-dots recovers. This fluorometric method allows for the determination of ALP activity in the range from 0.2 to 6.0 mU mL?1 with a detection limit of 0.16 mU mL?1. The IC50 value for the inhibitor Na3VO4 is 3.6 μM. The method is convenient and cost-effective. It does not require complicated operations and in our perception widens the scope of applications of C-dots in bioanalytical sciences.
关键词： cis-Diols,3-Aminophenylboronic acid,Enzyme inhibition,Fluorometry,Ascorbic acid,Ascorbic acid 2-phosphate,Sodium orthovanadate
更新于2025-11-19 16:46:39
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A gadolinium(III)-porphyrin based coordination polymer for colorimetric and fluorometric dual mode determination of ferric ions
摘要： A coordination polymer (CP) based nanoprobe is described for colorimetric and fluorometric (dual mode) determination of ferric ion. The method is making use of a nanosized Gd(III)?5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin coordination polymer that was prepared by a single-step hydrothermal procedure. The nanoprobe is monodisperse and has uniform size and good water solubility. It also exhibits strong fluorescence and magnetic resonance response. On exposure to Fe(III), the color of the solution changes from red to brown as the concentration of Fe(III) exceed 5 μM. Similarly, the red fluorescence of the probe (with excitation/emission peaks at 420/675 nm) decreases as concentrations of Fe(III) increase from 0.5 to 100 μM. The limit of detection is 98 nM in the fluorometric mode. The assay was applied to the determination of Fe(III) in fetal bovine serum samples.
关键词： Fluorometry,Metal-organic compound,Fe3+ detection,Colorimetry,Gd-coordinated
更新于2025-11-14 17:04:02
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Far-Red Spectrum of Second Emerson Effect: A Study Using Dual-Wavelength Pulse Amplitude Modulation Fluorometry
摘要： Non-additive enhancement of the photosynthesis excited by simultaneous illumination with far-red light and light of shorter wavelengths is called as “second Emerson effect”. Its action spectra are well-known as a photosynthetic yield’s dependence on light wavelength in red (630-690 nm) spectral region at a constant-wavelength far-red illumination near 700-715 nm. However, the opposite dependence of the photosynthetic yield’s of shorter constant-wavelength light (red or blue) on light wavelength in far-red (690-760 nm) spectral region was never studied. In this study the action spectrum of second Emerson effect was studied using a fast-Fourier dual-wavelength Pulse Amplitude Modulation (PAM) fluorometry. Chlorophyll fluorescence in ailanthus (Ailanthus altissima Mill.) leaves was excited with blue modulated light. Far-red induced decrease of fluorescence (fluorescence shift-FRIFS) was studied in response to illumination of leaves with a background light from 690 to 760 nm (10 nm step), calculating FRIFS = (F0-Fs)/F0, where F0-fluorescence measured without and Fs-with far-red light. Maximum FRIFS was observed at 720 nm (11.8%), but it still remained considerable at 740, 750 nm and a low FRIFS values were revealed at 690 and even at 760 nm. Measurements carried out with blue saturating flashes during and after far-red illumination showed the increase of quantum yield of Photosystem II (PSII), calculated as Fv/Fm at 720 nm background light. FRIFS had lower values under excitation with red modulating light. It is concluded that FRIFS is a result of a photochemical quenching caused by an additional selective far-red excitation of PSI in conditions when PSII is preferably excited by blue light thus leading the PSI to limit non-cyclic electron flow. The contradiction between the known absorption spectra of PSI-light harvesting complex I and the observed action spectrum of second Emerson effect (FRIFS spectrum) is discussed.
关键词： Photosystem II,Ailanthus Altissima,Photosystem I,Second Emerson Effect,Fast-Fourier PAM-Fluorometry,Far-Red Light,Thylakoid Electron Transport
更新于2025-11-14 15:30:11
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A turn-on fluorescent probe for vitamin C based on the use of a silicon/CoOOH nanoparticle system
摘要： The authors describe a fluorometric method for the turn-on determination of vitamin C (ascorbic acid). The blue fluorescence of silicon nanoparticles (SiNPs; with excitation/emission maxima at 350/450 nm) is found to be quenched by CoOOH nanoparticles (NPs). In the presence of vitamin C, the CoOOH NPs are decomposed by a redox reaction between the diol group of vitamin C and CoOOH NPs. As a result, fluorescence recovers. On the basis of this finding, a fluorometric method was designed for the turn-on detection of vitamin C. Under optimal conditions, the method has a low detection limit (0.47 μM) and a linear response in the 0.5 μM to 20 μM a concentration range. It was successfully applied to the determination of vitamin C in spiked red grape and orange juice, and in vitamin C tablets.
关键词： Fluorescence Bturn-on^ strategy,Cobalt oxyhydroxide nanoparticles,Fluorometry,Stern-Volmer plot,Surface energy transfer,Redox reaction,Inner filter effect,Quenching,Silicon nanoparticles
更新于2025-09-23 15:23:52
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Ovalbumin antibody-based fluorometric immunochromatographic lateral flow assay using CdSe/ZnS quantum dot beads as label for determination of?T-2 toxin
摘要： This work describes an anti-ovalbumin antibody-based lateral flow immunoassay (LFI) for T-2 toxin. The antibody uses a coating antigen as a bifunctional element for universality and introduces preincubation to improve the detection limits of the method. T-2 toxin and ovalbumin-modified T-2 toxin competitively binds on the anti-T-2 toxin monoclonal antibody modified on CdSe/ZnS quantum dot beads during preincubation. The modified T-2 toxin acts as a bifunctional element that forms immuno complexes during preincubation and combines with anti-ovalbumin antibody coated in the test line through the ovalbumin terminal. Fluorescence is detected at 610 nm on the test zone following photoexcitation at 365 nm. It has a reverse dose-effect relationship with the amount of T-2 toxin. The calibration plot is linear in the 20–110 fg mL?1 T-2 toxin concentration range, and the limit of detection (LOD) is 10 fg mL?1, which is lower by 8-fold than that of the traditional LFI system (LOD 80 fg mL?1) and one order of magnitude than those of LFIs with labels of colloidal gold nanoparticles (LOD 150 fg mL?1) or fluorophores (LOD 190 ng mL?1). Universality was verified through aflatoxin B1 detection using the established ovalbumin antibody-based LFI system (LOD 10 fg mL?1). The performance of the method was compared with that of established systems and a commercial ELISA kit (LOD 360 fg mL?1).
关键词： Fluorometry,Bifunctional element,Calibration plot,Sensitivity,Limit of detection,Aflatoxin B1,Preincubation
更新于2025-09-11 14:15:04
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Determination of the activity of alkaline phosphatase based on?aggregation-induced quenching of the fluorescence of?copper nanoclusters
摘要： A rapid method is described for synthesis of copper nanoclusters (CuNCs) by utilizing L-histidine as the stabilizer and ascorbic acid (AA) as the reductant. The CuNCs display blue-green fluorescence with excitation/emission peaks at 390/485 nm. A sensitive fluorometric assay was worked out for determination of alkaline phosphatase (ALP) activity. If the ALP substrate p-nitrophenylphosphate (PNPP) is enzymatically hydrolyzed, it forms p-nitrophenol (PNP) which reduces the fluorescence of CuNCs because its absorption band at 410 nm overlaps the excitation peak of CuNCs at 390 nm. In addition, the amino groups and imidazole groups on the surface of CuNCs possibly form a complex with the phenol groups of PNP. This induces aggregation-induced quenching of the fluorescence of CuNCs. The fluorescent probe has a linear analytical range that extends from 0.5 mU·mL?1 to 40 mU·mL?1 and a detection limit of 45 μU·mL?1.
关键词： Alkaline phosphatase,Aggregation-induced quenching,Fluorometry,Inner filter effect,L-Histidine,Copper nanoclusters
更新于2025-09-04 15:30:14
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Aluminum(III) triggered aggregation-induced emission of glutathione-capped copper nanoclusters as a fluorescent probe for creatinine
摘要： Glutathione-capped copper nanoclusters (CuNCs) are presented that display aggregation-induced emission (AIE). This feature was exploited for selective and sensitive quantification of creatinine (CRN) which is an important diagnostic parameter. In the presence of Al3+ ions, such CuNCs rapidly aggregate, and this induces enhanced a red emission. The AIE nature of CuNCs was proven via TEM and fluorimetry. On addition of CRN, the coordination between CRN and Al3+ ions led to the quenching of fluorescence due to weakening the AIE. The best fluorescence intensity was measured at excitation/emission peaks of 360/585 nm. Quenched fluorescence intensity showed a linear dependence on the concentrations of CRN in the range of 2.5–34 μgL?1 with a detection limit of 0.63 μgL?1. The sensing mechanism of probe for CRN detection is discussed. The probe was applied to the determination of CRN in spiked human serum samples and gave satisfactory results.
关键词： Nanosensor,Renal biomarker,Serum analysis,Fluorescent nanomaterials,Metal nanoclusters,Nanoprobe,Paired t-test,Fluorometry,Real sample analysis
更新于2025-09-04 15:30:14
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Interaction Between Phenanthorline and Proteins: A Fluorescence Spectroscopy-Based Study
摘要： Serum albumin with cardinal physiological functions is the most abundant protein in blood plasma. The concentration of serum albumin is an index of physical health and disease. Spectrophotometry was always used to determinate the concentration of serum albumin. In present study, a novel method for the determination of proteins was established based on the enhanced fluorescence intensity derived from the binding interaction of phenanthorline with proteins in the CH3COOH-CH3COONa buffer at pH 5.98. Underlying the excitation wavelength at 270 nm and the emission wavelength at 366 nm, the enhancement of fluorescence intensity was proportional to the concentration of proteins. The linear range for the calibration graph of human serum albumin was 20-160 μg/mL and the detection limit was 24.12 μg/mL. The recovery was 95.0-105.3 %. The method was sensitive, accurate, required fewer samples and was tolerant of many foreign substances.
关键词： Human serum albumin,Fluorometry,Phenanthorline
更新于2025-09-04 15:30:14
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Target-switched triplex nanotweezer and synergic fluorophore translocation for highly selective melamine assay
摘要： This paper describes a triplex DNA nanotweezer to specifically capture melamine (MEL). The triplex-forming oligonucleotide (TFO) arm can be switched from the open state to the closed state once MEL binds to the abasic site (AP site) in duplex via the bifacial hydrogen bonding with thymines. Following this nanotweezer operation, the AP site-bound fluorophore is translocated to the terminal triplet to subsequently light up the nanotweezer. The TFO arm is found to be pivotal for permitting the AP site binding. The synergic processes of target competition and fluorophore translocation support a high selectivity for the MEL assay even against the inherent adenosine and the MEL hydrolysis products. Chelerythrine is employed as the fluorescent probe. The detection limit of MEL was estimated to be about 140 nM assuming a signal-to-noise ratio of 3. It was applied to the determination of MEL in spiked milk samples without any separation procedure. Conceivably, this method opens a new avenue towards highly selective triplex-based sensors by making use of other commercially available DNA modifications for recognizing other analytes.
关键词： Milk,Chelerythrine,Switch,Fluorescence,Hydrogen bonding,DNA,Fluorometry,Abasic site
更新于2025-09-04 15:30:14