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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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Suppression of riboflavin-sensitized singlet oxygen generation by l-ascorbic acid, 3-O-ethyl-l-ascorbic acid and Trolox
摘要： Riboflavin (RF), a water-soluble vitamin B2, is an endogenous singlet oxygen photosensitizer in human skin and eye. Time profiles of the near-infrared phosphorescence of singlet oxygen generated by RF have been measured in the absence and presence of L-ascorbic acid (AA, vitamin C), 3-O-ethyl-L-ascorbic acid (3-EtAA) and Trolox (TX, a water-soluble analogue of vitamin E) in phosphate buffer (pH 6.8). These substances suppress the RF-photosensitized singlet oxygen generation. For example, the quantum yield of singlet oxygen generation is decreased to a third by adding 0.4 mmol dm?3 AA or TX (the concentration of dissolved oxygen in air-saturated water is 0.27 mmol dm?3). AA and TX are more efficient suppressors of RF-photosensitized singlet oxygen generation than 3-EtAA. The bimolecular rate constants for quenching of the excited singlet and triplet states of RF by AA, 3-EtAA and TX have been determined through measurements of fluorescence and transient absorption. These measurements suggest that the observed suppression is due to the quenching of the excited singlet and triplet states of RF by AA, 3-EtAA and TX. The bimolecular rate constants for quenching of singlet oxygen by AA, 3-EtAA and TX were determined to be 1.8 × 108, 0.27 × 108, and 4.4 × 108 mol?1 dm3 s?1, respectively.
关键词： Trolox,Riboflavin,Singlet oxygen,3-O-ethyl-L-ascorbic acid,L-ascorbic acid
更新于2025-09-23 15:23:52
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Cu-Zn and Cu-Ni Bimetallic Particles Fabricated Using Ascorbic Acid and Its Role in Photodegradation of Methyl Orange
摘要： Chemical reduction of metal salts using ascorbic acid (vitamin C) is a new and green approach in which ascorbic acid serve dual role of reducing and capping agent. Copper, zinc and nickel salts were reduced by ascorbic acid to give bimetallic nanoparticles. SEM images highlight the aggregation of nanoparticles, which is due to the high surface energy of the particles in nano range. Bimetallic particles fabricated are in the weight ratio of 4:1. Subsequent shift of surface plasma resonance band and XRD peaks indicate that the particles are not just a physical mixture of mono metallic particles. UV-visible spectra and XRD result rule out the alloy nature of the particles. Average size of the particles were calculated using XRD data and are in nano scaled. Size of the Cu, Cu-Zn and Cu-Ni particles as calculated by using Scherrer’s equation are 43.47, 38.4 and 43.5 nm, respectively. In this work photo degradation of methyl orange has been studied to demonstrate the catalytic properties of mono and bimetallic particles. Bimetallic particles have superior catalytic application as compared to monometallic particles. These alloying of metals might have result in change of certain electronic configuration, which significantly increase the catalytic application of bimetallic nanoparticles.
关键词： Methyl orange,Ascorbic acid,Bimetallic,Catalytic properties
更新于2025-09-23 15:23:52
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The Sonogel-Carbon-PEDOT Material: An Innovative Bulk Material for Sensor Devices
摘要： The synthesis of a new bulk material based on silicon oxide and poly-(3,4-ethylenedioxythiophene) (PEDOT), the Sonogel-Carbon-PEDOT material, is carried out. The main purpose is to obtain a bare conducting material, aided by statistical experimental design, able to be used as transducer for electrochemical devices. This new material tries also to solve out the degradation and fouling drawbacks related to PEDOT-based layer devices by simply polishing its surface in a gently way. The resulting Sonogel-Carbon-PEDOT material shows excellent electrochemical properties, renewable surface and stability by using simple, low cost, and versatile synthesis method. As far as we are concerned, this is the first time that this kind of bulk material is reported. The resulting material was characterized by different techniques: SEM, EDS and Raman spectroscopy. Sonogel-Carbon-PEDOT was also electrochemically characterized for the assessment of the electrochemical performance of the resulting sensor device. Ascorbic acid was selected as reference analyte, obtaining good sensitivity and limit of detection: 319.8 μA mM-1cm-2 and 6.42 μM, respectively, in the concentration range 0.01–3.45 mM. Furthermore, repeatability and reproducibility studies (RSD<3%), were also very satisfactory. Finally, the Sonogel-Carbon-PEDOT sensor was successfully applied to the determination of ascorbic acid in a pharmaceutical formulation and biological samples, obtaining good recovery percentage (95–105%).
关键词： electrochemical properties,sensor devices,Sonogel-Carbon-PEDOT,conducting polymers,ascorbic acid
更新于2025-09-23 15:22:29
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Non-oxidation reduction strategy for highly selective detection of ascorbic acid with dual-ratio fluorescence and colorimetric signals
摘要： Ascorbic acid (AA), one of the most important vitamins, acts a critical role in various physiological reactions and is involved in many diseases. Thus, the development of highly selectivity methods for detecting AA level with the presence of different reducing substances is of great significance in complicated serum matrix. In this paper, a non-oxidation reduction regulation (NRR) strategy was designed to construct a novel dual-ratio fluorescence and colorimetric dual-readout assay for highly selective detection of AA. The strategy involves three processes: Ag+ oxidated o-phenylenediamine (OPD) to 2,3-diaminophenazine (OPDox), AA inhibited the generation of OPDox and the AA was oxidized to dehydroascorbic acid (DHAA). The specific performance of DHAA NRR, due to the condensation reaction between dicarbonyl group of DHAA and diamine group of OPD, that is confirmed by ESI-MS and 1H NMR spectra analysis, can remarkably enhance the selectivity of AA detection. Additionally, the proposed method based on NRR strategy not only provides a sensing platform for probing AA but also shows promising outlook in biomedical studies.
关键词： O-phenylenediamine,Non-oxidation reduction regulation,Ascorbic acid,Dual-ratio,Dual-readout
更新于2025-09-23 15:21:21
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Oral ascorbic acid 2-glucoside prevents coordination disorder induced via laser-induced shock waves in rat brain
摘要： Oxidative stress is considered to be involved in the pathogenesis of primary blast-related traumatic brain injury (bTBI). We evaluated the effects of ascorbic acid 2-glucoside (AA2G), a well-known antioxidant, to control oxidative stress in rat brain exposed to laser-induced shock waves (LISWs). The design consisted of a controlled animal study using male 10-week-old Sprague-Dawley rats. The study was conducted at the University research laboratory. Low-impulse (54 Pa?s) LISWs were transcranially applied to rat brain. Rats were randomized to control group (anesthesia and head shaving, n = 10), LISW group (anesthesia, head shaving and LISW application, n = 10) or LISW + post AA2G group (AA2G administration after LISW application, n = 10) in the first study. In another study, rats were randomized to control group (n = 10), LISW group (n = 10) or LISW + pre and post AA2G group (AA2G administration before and after LISW application, n = 10). The measured outcomes were as follows: (i) motor function assessed by accelerating rotarod test; (ii) levels of 8-hydroxy-2’-deoxyguanosine (8-OHdG), an oxidative stress marker; (iii) ascorbic acid in each group of rats. Ascorbic acid levels were significantly decreased and 8-OHdG levels were significantly increased in the cerebellum of the LISW group. Motor coordination disorder was also observed in the group. Prophylactic AA2G administration significantly increased the ascorbic acid levels, reduced oxidative stress and mitigated the motor dysfunction. In contrast, the effects of therapeutic AA2G administration alone were limited. The results suggest that the prophylactic administration of ascorbic acid can reduce shock wave-related oxidative stress and prevented motor dysfunction in rats.
关键词： ascorbic acid 2-glucoside,laser-induced shock waves,traumatic brain injury,Oxidative stress,motor dysfunction
更新于2025-09-23 15:21:01
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A novel fluorescent probe for ascorbic acid based on seed-mediated growth of silver nanoparticles quenching of carbon dots fluorescence
摘要： A novel, economic, and eco-friendly method of detecting ascorbic acid (AA) with excellent sensitivity was developed. The method took advantage of the fluorescence of carbon quantum dots (CDs) decreasing as the AA concentration increased through interactions between AA and Ag(I) in the presence of silver nanoparticle (AgNP) seeds, producing more AgNPs and allowing fluorescence resonance energy transfer between the AgNPs and the CDs. The change in the fluorescence intensity when AA was added was proportional to the AA concentration over the range 0–9.0 μM. The AA detection limit was 0.2 μM. This approach is a new method for determining the concentration of AA.
关键词： Fluorescence,Carbon dots,Ascorbic acid,Silver nanoparticles
更新于2025-09-23 15:21:01
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An efficient visible-light-responsive surface charge transfer complex AA-TiO2 based dye-sensitized solar cell
摘要： This work investigated a new strategy for visible light responsive dye-sensitized solar cell: the ligand-to-metal charge transfer (LMCT) takes place between TiO2 nanoparticles and ascorbic acid (AA). The surface LMCT complex AA-TiO2 extended the spectral responsive range to 800 nm and exhibited prominent visible light activity, enhancing utilization of the solar spectrum. The optimal photovoltaic conversion efficiency of the visible-light-responsive AA-TiO2 based dye-sensitized solar cell reach value of 3.50%. The low-cost, non-toxic and environment friendly surface adsorbate AA will demonstrate a feasible approach for replacing the most common used ruthenium complex dyes, thereby offering a strategy for development of low-cost and high efficiency DSSCs.
关键词： Dye-sensitized solar cell,Surface complex,Ligand-to-metal charge transfer (LMCT),Ascorbic acid,Visible light activity
更新于2025-09-23 15:19:57
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MPA-CdTe quantum dots as a??on-off-ona?? sensitive fluorescence probe to detect ascorbic acid via redox reaction
摘要： Mercaptopropionic acid (MPA) capped CdTe quantum dots (MPA-CdTe QDs) were synthesized in aqueous medium by hydrothermal method, which modified by Fe3+ could be used as a fluorescent probe to detect ascorbic acid (AA). MPA-CdTe QDs fluorescence probe could be used as successive sensor for metal ions and AA with "on-off-on" process. The fluorescence of QDs was quenched after adding Fe3+ to MPA-CdTe QDs. Then, the fluorescence of the Fe3+@MPA-CdTe QDs can be sensitively turned on by AA to give an "on–off–on" fluorescence response according to the oxidation–reduction between Fe3+ and AA. There was a linear relationship between fluorescence intensity quenching value and the concentration of Fe3+ in the range of 2–10 μM since Fe3+ sensitively reacted with CdTe QDs. The linear detection range for AA was 0.1–1 μM with a limit of detection of 6.6 nM. The principle is proved by fluorescence emission spectroscopy, nuclear magnetic resonance spectroscopy. The proposed method is successfully used to detect the AA in human plasma sample.
关键词： CdTe quantum dots,Redox reaction,Fluorescent probe,Ascorbic acid
更新于2025-09-23 15:19:57
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Understanding the Citric Acid-Urea Co-Directed Microwave Assisted Synthesis and Ferric Ion Modulation of Fluorescent Nitrogen Doped Carbon Dots: A Turn On Assay for Ascorbic Acid
摘要： Herein, nitrogen doped carbon dots (NCDs) were synthesised from citric acid and urea via a previously reported microwave assisted route. The NCDs shows emission maximum at 500 nm on excitation at 400 nm. The fluorescence of NCDs decreases slightly with increase in basicity of solution up to pH 7.5 and then increases again after pH 8.5, along with a blue-shift in tested alkaline pH. This pH dependent blue-shift indicates the presence of both carboxyl?carboxylate and phenol?phenolate prototropic equilibrium in NCDs. Due to the special interaction of these phenolates and carboxylates on NCDs surface with di- or tri- valent heavy transition metal ions; it is demonstrated that ferric ion (Fe3 + ion) can quench the fluorescence of NCDs. This Fe3 + induced static quenching of NCDs is a collaborative effect of inner filter effect, aggregation and ferromagnetism. However, Ascorbic acid (AA) can recover the fluorescence of Fe3 + quenched NCD with detection limit as low as 96 μM. This detection strategy has good selectivity towards AA over other antioxidants, saccharides, proteins and neurotransmitters. Furthermore, (spiked) human serum and (spiked) human urine were analysed and found good recovery percentage.
关键词： Fluorescence,Ascorbic Acid,Biosensor,Inner Filter Effect,Iron(III),Carbon Dots
更新于2025-09-19 17:15:36