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μ-Oxo-bis[tetrakis(t-butyl)phthalocyaninatoiron] (1) reacts with L-ascorbic acid (LAA) in pyridine containing CH₂Cl₂ under strictly anaerobic conditions to yield dehydroascorbic acid (DHA) and Pc^tFe^II(py)₂ (Pc^t = tetrakis(t-butyl)phthalocyaninato dianion). The reaction is quantitative with a 1:1 LAA/1 stoichiometric ratio. This result can be explained only if it is assumed that the μ-oxo complex 1 (reacting as the bispyridine adduct) is an iron(III) complex able to oxidise LAA to DHA quantitatively. Present findings definitively rule out the alternative iron(II) structure H₂[(Pc^tFe)₂O] which has been assigned to compound 1 by other authors.

Electrochemical behaviors of dopamine and ascorbic acid have been studied at the carbon nanotube electrode using cyclic voltammetry. Electrocatalysis has been found for dopamine redox reactions at the carbon nanotube electrode in comparison with the glassy carbon electrode. A well-defined oxidative peak for ascorbic acid was observed at the carbon nanotube electrode with the peak potential negative shift versus the glassy carbon electrode. The important discover was that the carbon nanotube electrode can be used to detect low level of dopamine selectively with high sensitivity in the presence of a large excess of ascorbic acid in the acidic media and in the physiological pH buffer solution as well.

In this paper, we report a simple sensing strategy for electrochemical determination of ascorbic acid (AA) using a combination of polypyrrole (PPy) thin film and palladium particles composites deposited onto $n$-doped silicon (Si) substrate. A two-step electrochemical process was employed to synthesize the composite films: At first, PPy film (average thickness 200nm) was electrogenerated on Si substrate from an organic solution of the pyrrole under galvanostatic conditions. Secondly, palladium particles were electrodeposited on PPy/Si surface from a separate solution by chronoamperometry technique. The surface morphology analysis of the obtained composites shows a uniform dispersion of palladium particles onto the polymer matrix and reveals that the electrodeposition time has a significant effect on the amount and size of the incorporated palladium particles. The electrochemical reactivity of the Pd–PPy/Si-modified electrodes towards the oxidation of AA was studied by cyclic voltammetry method in 0.1M, pH 7.0 phosphate buffer solution. The oxidation current was proportional to the concentration of AA in the range of 0.5–10mM with a detection limit of 0.2mM.

In this work, a modified electrode of copper-polypyrrole (Cu-PPy) is elaborated by charging the polymer matrix by Cu particles. The response to ascorbic acid (AA) of this material was tested. The results show good performances. The results indicated a sensitive oxidation peak current of AA on the modified electrode. The success of this application led us to study the nucleation mechanism of copper on the PPy surface which permits to obtain this response. Nucleation and growth of electrodeposited copper onto PPy substrate have been studied in an aqueous solution of 0.01M CuCl₂ and 1M KCl by means of electrochemical methods: cyclic voltammetry, chronoamperometry, and using atomic force microscopy (AFM). The model described by Scharifker and Hills was used to analyze current-time transients. According to this model, the nucleation and growth kinetics at the initial stages of deposition process involve an instantaneous nucleation followed by three-dimensional (3D) growth mechanism.

Objectives: To investigate the effectiveness of vitamin C and E supplementation in remission of the symptoms of chronic degenerative arthritis (osteoarthritis) of the knee. Design: A pilot controlled trial conducted from December 2009 until April 2011 among 46 patients diagnosed with osteoarthritis (OA) in one or both knees. Intervention: Patients were randomly assigned to two different treatment groups and were either supplemented with ascorbic acid 1 gr × 2 daily per os together with vitamin E 100 mg × 3 daily per os or they were treated with meloxicam tabs 15 mg × 1 daily per os. Main outcome measures: A. Clinical markers: functionality of the knee (WOMAC index), pain (using a pain visual analogue scale) and the deficit in knee flexion and extension B. Laboratory markers: total antioxidant capacity (TAC) and concentration of malonyldialdehyde (MDA) in the synovial fluid. Results: Twenty patients were randomly allocated into each of the two intervention groups. The treatment lasted for 20 days and the patients' status was evaluated every 10 days. The condition of the patients' knees in both treatment groups presented a significant improvement as recorded by the clinical markers; accompanied by an enhancement of TAC but with no effect on MDA levels. Conclusions: Administration of vitamins C and E has a similar effect in the remission of the symptoms of the OA in the knee, comparable to that of the treatment with meloxicam, but without the possible side effects and thus can be proposed as adjuvant therapy.

Different porphyrins were used for the design of seven carbon paste and seven diamond paste based microelectrodes, which were employed for the determination of ascorbic acid in pharmaceutical and beverages samples using differential pulse voltammetry (DPV). The limits of detection lie between 1.1 × 10^-14 and 5.1 × 10^-7 M while the sensitivities were between 3.07 pA/M and 1285.18 A/M. Ascorbic acid was recovered reliable from pharmaceutical and beverages samples in percentages higher than 92.00% and 91.50%, respectively. The surface of the microelectrodes can easily be renewed by simple polishing, obtaining a fresh surface ready for use in a new assay.

Carbonaceous electrodes of dilithium phthalocyanine were prepared using graphite, carbon microspheres and multiwall carbon nanotubes. The electrochemical behavior of the dilithium bisphthalocyanine electrodes was found to be dependent on the nature of the carbonaceous material and on the nature of the electrolytic solution. The electrocatalytic properties of the dilithium phthalocyanine electrodes for oxidation of ascorbic acid were evidenced by the enhancement of the oxidation peak current, (~10 fold compared to the bare carbon electrodes) and the decrease of the oxidation potential at which oxidation of ascorbic acid takes place. The combined use of multiwall carbon nanotubes and dilithium phthalocyanine produces a synergistic effect that improves the electrocatalytic effect towards ascorbic acid.

Magnetic targeting, which utilizes a magnetic field to specifically deliver therapeutic agents to the targeted regions, can greatly improve the treatment efficiency. Herein, ibuprofen-loaded brain targeting magnetic nanoparticles (AA-Ibu-PEG-DA@MNPs) modified with ascorbic acid (AA) for central nervous system (CNS) drug delivery was designed and synthesized in order to effectively deliver ibuprofen to the brain through Na${}^{+}$-dependent vitamin C transporter 2 (SVCT₂) and glucose transporter 1 (GLUT₁). The brain targeting magnetic nanoparticles, AA-Ibu-PEG-DA@MNPs, have a particle size of 82.5nm, 2% drug loading capacity and limited cytotoxicity against bEnd.3 cells. What’s more, the nanoparticles maintained the magnetic property with a saturation magnetization level at 52.17emu/g and could release ibuprofen when incubated in different mediums, including various buffers, mice plasma and brain homogenate. The results indicate that the magnetic nanoparticles may have the potential to be a promising approach to selectively deliver drugs into the brain. This study may be conducive to the field of CNS drugs delivery.

A simple pyrolysis, activation and hydrothermal method was utilized to synthesize composite materials (Fe₃O₄/SFP) of ferroferric oxide and nitrogen self-doped sunflower plate-derived carbon for the simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The Fe₃O₄/SFP had synergistic catalytic effect on target molecules, and the oxidation peak potential of AA, DA and UA was well distinguished in the differential pulse voltammetry determination. Under the optimal conditions, the linear response ranges of AA, DA and UA are 3–150$\mu$M, 5–450$\mu$M and 15–1200$\mu$M, respectively. The detection limits of AA, DA and UA ($S$/$N=3$) are 1.0$\mu$M, 0.4$\mu$M and 1.48$\mu$M, respectively, and the sensitivity is 1.87$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (3–20$\mu$M) and 0.64$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (20–150$\mu$M) for AA, 3.90$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (5–20$\mu$M) and 1.21$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (20–450$\mu$M) for DA and 1.12$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (15–100$\mu$M) and 0.31$\mu \mathrm{\text{A}}\cdot \mu {\mathrm{\text{M}}}^{-1}\cdot {\mathrm{\text{cm}}}^{-2}$ (100–1200$\mu$M) for UA. In addition, satisfactory results have been obtained for the determination of AA, DA and UA in normal human serum, which provides a new research direction for the construction of electrochemical sensors in the future.

A turn-on fluorometric probe is designed for the determination of ascorbic acid (AA) based on the inner filter effect (IFE) between CaF₂:${\text{Yb}}^{3+}$, ${\text{Er}}^{3+}$ upconversion nanoparticles (CaF₂:${\text{Yb}}^{3+}$, ${\text{Er}}^{3+}$ NPs) and the oxidized 3, $3^{\prime }$, 5, $5^{\prime }$-tetramethylbenzidine (oxTMB). The colorless TMB can be oxidized by H₂O₂/${\text{Cu}}^{2+}$ to blue oxTMB. Under 980 nm photoexcitation, CaF₂:${\text{Yb}}^{3+}$, ${\text{Er}}^{3+}$ NPs can emit red light, which can be absorbed by the blue oxTMB, leading to the fluorescence quenching at 657 nm. As AA can reduce the blue oxTMB to colorless TMB, the fluorescence at 657 nm can be recovered with the addition of AA, which can accomplish the detection towards AA. The linear detection range of AA is from 1 to 30 $\mu$M, and the limit of detection (LOD) of AA is 0.1 $\mu$M.

A layered nanocomposite CoTMPyP/NbWO₆ was fabricated by exfoliation/restacking method. The structure and morphology of LiNbWO₆, HNbWO₆ and CoTMPyP/NbWO₆ were characterized by XRD, SEM, TEM, EDS, UV-Vis and IR. It indicated that the CoTMPyP molecules were arranged about 67^∘ between the layers of [NbWO${}_6{]}^{-}$. Moreover, the Zeta potential of [NbWO${}_6{]}^{-}$ colloidal dispersion is $-45.7$mV, indicating that the colloidal suspension exfoliated by TBAOH solution is stable. Meanwhile, the cyclic voltammetry (CV) and the differential pulse voltammetry (DPV) measurements were used to explore the electrochemical properties of CoTMPyP/NbWO₆ nanocomposite modified glass carbon electrode (GCE). The modified GCE exhibited excellent electrocatalytic activity toward ascorbic acid (AA) oxidation and the oxidation reaction was proved to be a diffusion-controlled process. DPV measurements demonstrated that the CoTMPyP/NbWO₆ modified electrode detects AA linearly over a concentration range of $7.49\times 10^{-5}$ to $2.89\times 10^{-3}$molL${}^{-1}$ with a detection limit of $2.5\times 10^{-5}$molL${}^{-1}$ at a signal-to-noise ratio of 3.0.

The guest molecule trans-[2-(2,2,3,3,4,4,4-heptafluorobutylamino) ethyl]-{2-[4-(4-hexanobenzazo)-phenoxy] ethyl} -dimethylammonium (abbreviated as C₃F₇-azo${}^{+}$Br${}^{-}$) were inserted into the K ₄Nb₆O${}_{17}$laminated by the guest–guest exchange method to synthesize C₃ F₇-azo${}^{+}$/Nb₆ O${}_{17}$type-A nanocomposite with excellent electrochemical properties. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform infrared (FTIR) spectrometer and energy dispersive spectroscopy (EDS) were used to characterize the structure and morphology of nanocomposite C₃F₇-azo${}^{+}$/Nb ₆O${}_{17}$. C₃F₇-azo${}^{+}$ions were speculated to form bilayer between the [Nb₆O${}_{17}$ ]${}^{4-}$lamellar at an angle of $51.1^{\circ }$ by morphology analysis and lamellar spacing calculation. This nanocomposite was used to fabricate an electrochemical sensor for simultaneous detection of dopamine (DA) and ascorbic acid (AA). Differential pulse voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy in N₂-saturated phosphate buffered solution (0.1 M, pH = 5) demonstrated excellent electrocatalytic activity. The sensor achieved detection limits of 1.74 $\mu$M for DA and 1.57 $\mu$M for AA.

Ag@C core–shell structures were prepared using hydrothermal methods by AgNO₃ reduction with ascorbic acid in the presence of polyacrylamide (PAM). Temperature plays a key role in the formation of the core–shell structures. The roles of reactants, surfactant concentrations and reaction time on the morphologies of core–shell nanoparticles were investigated in detail. This synthetic method is one-pot synthesis, which is fast, high-yield and environmental-friendly for fabrication of Ag@C core–shell structures. The surface properties of core–shell Ag@C nanoparticles were characterized by Raman spectroscopy.

Bioartificial biodegradable materials were prepared mixing chitosan (CHI) and poly(vinyl alcohol) (PVA), then manufactured as films, and finally cross-linked with glutaraldehyde (GTA), both in the absence and in the presence of the edible hexa-alcohol sorbitol (SOR), as a plasticizer. The release of the components into water was tested by high performance liquid chromatography (HPLC); no release of CHI and scarce release of PVA were found. The water uptake was tested by measuring the swelling of the materials, after incubating them for 20 h in an atmosphere saturated with water vapor at 37°C. The swelling percentage increases with increasing CHI content in the blends, although it is the less hydrophilic polymer. This behavior was attributed to the difficulty of water to diffuse through the crystalline PVA structure, which is partially altered in the blends. The addition of SOR enhances the water sorption, as expected. The biodegradability of the materials was tested using the specific enzyme chitosanase, and was found to depend on the blend composition, as well as to be enhanced by the addition of SOR. The initial degradation rates were calculated; the maximum rates were found when the CHI to PVA ratio was 80:20 for all systems. The results of the enzymatic degradation generally agree with those of the swelling. The cross-linked blends were also tested as drug-delivery systems. The drugs chosen were the vitamin L-ascorbic acid (AsA) and the anti-cancer drug paclitaxel (PTX). The effective diffusion coefficients, Deff, were evaluated for the release of both the drugs from each material. Those of AsA are greater, of many powers of ten, than those of PTX, owing mainly to the hydrophilic nature of the first drug and to the hydrophobic of the second one. In conclusion, these materials seem available for biomedical use.

Burn injuries could be local or systemic problems, so multiple disciplines should be considered, including nutrition. Vitamin C is a cofactor of prolyl and lysyl hydroxylation for collagen maturation and ceramide synthesis and an important water-soluble free radical scavenger. Clinically, supplement of vitamin C is part of burn care for improving the healing process and decreasing further damage. With modified interdigitated microelectrode plate (IMP), electrical burn of MDCK cells was produced with constant current for few seconds. Healing process of cells damaged by different duration of direct constant current and damaged cells treated with 100 μM vitamin C were recorded by modified IMP and impedance-sensing system. The rate of change of conductivity is fast in the group of shorter exposure time and vitamin C-treated cells. Compared with the result of MTT test, we concluded that vitamin C decreased the duration of healing through increase cell proliferation.

Hot air drying, vacuum drying and low-pressure superheated steam drying (LPSSD) of Indian gooseberry flake were carried out at various drying temperatures (65 and 75°C) and absolute pressures (7, 10 and 13 kPa) to monitor the drying kinetics and quality changes, in terms of color changes and antioxidant activity, of the product. The dried gooseberry flake was then soaked in hot water at 70, 80 and 90°C to prepare Indian gooseberry tea. In terms of the drying kinetics, the drying temperature had an effect on the moisture reduction rate of the samples in all cases. Vacuum drying, however, took shorter time to dry the product to the desired moisture content. Regarding the nutritional quality of the dried flake, it was found that the amount of ascorbic acid in the flake dried by vacuum drying was higher than those dried by hot air drying and LPSSD. However, LPSSD could retain flavonoid compounds better than did other drying techniques. On the other hand, total polyphenolic compounds and the total antioxidant activity of the dried flake were not significantly different among all cases. Regarding the release of antioxidants from the flake during tea preparation, no significant difference was observed between using the water temperature of 70, 80 and 90°C. Due to the more porous structure of LPSSD flake, however, higher compound degradation was noted. Nevertheless, it could still be concluded that drying the flake by LPSSD at 75°C and 7 kPa could best retain the active compounds, i.e., 62% of ascorbic acid, 91% of flavonoid compounds, 81% of total polyphenolic compounds and 83% of antioxidant activity; appropriate water temperature and time for tea preparation was 90°C and 5 minutes, respectively.