Showing papers on "Ascorbic acid published in 2021"

Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical Trial.

Abstract: Importance There is limited evidence regarding early treatment of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection to mitigate symptom progression. Objective To examine whether high-dose zinc and/or high-dose ascorbic acid reduce the severity or duration of symptoms compared with usual care among ambulatory patients with SARS-CoV-2 infection. Design, Setting, and Participants This multicenter, single health system randomized clinical factorial open-label trial enrolled 214 adult patients with a diagnosis of SARS-CoV-2 infection confirmed with a polymerase chain reaction assay who received outpatient care in sites in Ohio and Florida. The trial was conducted from April 27, 2020, to October 14, 2020. Intervention Patients were randomized in a 1:1:1:1 allocation ratio to receive either 10 days of zinc gluconate (50 mg), ascorbic acid (8000 mg), both agents, or standard of care. Outcomes The primary end point was the number of days required to reach a 50% reduction in symptoms, including severity of fever, cough, shortness of breath, and fatigue (rated on a 4-point scale for each symptom). Secondary end points included days required to reach a total symptom severity score of 0, cumulative severity score at day 5, hospitalizations, deaths, adjunctive prescribed medications, and adverse effects of the study supplements. Results A total of 214 patients were randomized, with a mean (SD) age of 45.2 (14.6) years and 132 (61.7%) women. The study was stopped for a low conditional power for benefit with no significant difference among the 4 groups for the primary end point. Patients who received usual care without supplementation achieved a 50% reduction in symptoms at a mean (SD) of 6.7 (4.4) days compared with 5.5 (3.7) days for the ascorbic acid group, 5.9 (4.9) days for the zinc gluconate group, and 5.5 (3.4) days for the group receiving both (overallP = .45). There was no significant difference in secondary outcomes among the treatment groups. Conclusions and Relevance In this randomized clinical trial of ambulatory patients diagnosed with SARS-CoV-2 infection, treatment with high-dose zinc gluconate, ascorbic acid, or a combination of the 2 supplements did not significantly decrease the duration of symptoms compared with standard of care. Trial Registration ClinicalTrials.gov Identifier:NCT04342728

Effect of Vitamin C, Thiamine, and Hydrocortisone on Ventilator- and Vasopressor-Free Days in Patients With Sepsis: The VICTAS Randomized Clinical Trial

Abstract: Importance Sepsis is a common syndrome with substantial morbidity and mortality. A combination of vitamin C, thiamine, and corticosteroids has been proposed as a potential treatment for patients with sepsis. Objective To determine whether a combination of vitamin C, thiamine, and hydrocortisone every 6 hours increases ventilator- and vasopressor-free days compared with placebo in patients with sepsis. Design, setting, and participants Multicenter, randomized, double-blind, adaptive-sample-size, placebo-controlled trial conducted in adult patients with sepsis-induced respiratory and/or cardiovascular dysfunction. Participants were enrolled in the emergency departments or intensive care units at 43 hospitals in the United States between August 2018 and July 2019. After enrollment of 501 participants, funding was withheld, leading to an administrative termination of the trial. All study-related follow-up was completed by January 2020. Interventions Participants were randomized to receive intravenous vitamin C (1.5 g), thiamine (100 mg), and hydrocortisone (50 mg) every 6 hours (n = 252) or matching placebo (n = 249) for 96 hours or until discharge from the intensive care unit or death. Participants could be treated with open-label corticosteroids by the clinical team, with study hydrocortisone or matching placebo withheld if the total daily dose was greater or equal to the equivalent of 200 mg of hydrocortisone. Main outcomes and measures The primary outcome was the number of consecutive ventilator- and vasopressor-free days in the first 30 days following the day of randomization. The key secondary outcome was 30-day mortality. Results Among 501 participants randomized (median age, 62 [interquartile range {IQR}, 50-70] years; 46% female; 30% Black; median Acute Physiology and Chronic Health Evaluation II score, 27 [IQR, 20.8-33.0]; median Sequential Organ Failure Assessment score, 9 [IQR, 7-12]), all completed the trial. Open-label corticosteroids were prescribed to 33% and 32% of the intervention and control groups, respectively. Ventilator- and vasopressor-free days were a median of 25 days (IQR, 0-29 days) in the intervention group and 26 days (IQR, 0-28 days) in the placebo group, with a median difference of -1 day (95% CI, -4 to 2 days; P = .85). Thirty-day mortality was 22% in the intervention group and 24% in the placebo group. Conclusions and relevance Among critically ill patients with sepsis, treatment with vitamin C, thiamine, and hydrocortisone, compared with placebo, did not significantly increase ventilator- and vasopressor-free days within 30 days. However, the trial was terminated early for administrative reasons and may have been underpowered to detect a clinically important difference. Trial registration ClinicalTrials.gov Identifier: NCT03509350.

A review of recycling spent lithium-ion battery cathode materials using hydrometallurgical treatments

Abstract: With the increasing market share of lithium-ion battery in the secondary battery market and their applications in electric vehicles, the recycling of the spent batteries has become necessary. The number of spent lithium-ion batteries grows daily, which presents a unique business opportunity of recovering and recycling valuable metals from the spent lithium-ion cathode materials. Various metals including cobalt, manganese, nickel, aluminum, and lithium can be extracted from these materials through leaching with chemicals such as hydrochloric acid ( HCl ), nitric acid ( HN O 3 ), sulfuric acid ( H 2 S O 4 ), oxalate ( H 2 C 2 O 2 ), DL-malic acid ( C 4 H 5 O 6 ), citric acid ( C 6 H 8 O 7 ), ascorbic acid ( C 6 H 8 O 6 ), phosphoric acid ( H 3 P O 4 ) or acidithiobacillus ferrooxidans. This paper provides a comprehensive review on the available hydrometallurgical technologies for recycling spent lithium-ion cathode materials. The recycling processes, challenges and perspectives reported to date and recycling companies in the market are summarized. To accelerate the development of battery recycling technology toward commercialization, some potential research directions are also proposed in this paper.

Antibacterial, Cytotoxicity and Larvicidal Activity of Green Synthesized Selenium Nanoparticles Using Penicillium corylophilum

Abstract: Anopheles mosquitoes became one of the biggest problems threaten human life through causing malaria disease. Hereby, Selenium nanoparticles (Se-NPs) as anti-victor malaria were fabricated for the first time through Penicillium corylophilum in presence of ascorbic acid as a reducing agent. Antibacterial versus pathogenic Gram +Ve and Gram −Ve bacteria, as well, in vitro cytotoxicity against two types of cell lines (normal Wi 38 and cancer Caco-2) were explored prolonging with their larvicidal activity towards Anopheles stephensi mosquitoes. Se-NPs is characterized by UV–Vis spectroscopy, FT-IR, TEM, EDX, XRD, DLS. Results affirmed the ability of Penicillium corylophilum to build up Se-NPs in spherical shape with average size 29.1–48.9 nm. In addition, Se-NPs exhibited broad spectrum activity against pathogenic Gram +Ve and Gram −Ve bacteria, while the results obtained from cytotoxicity evaluation signified clearly that, alteration occurred in the cells was represented as loss of their typical shape, partial or complete loss of monolayer, granulation, shrinking or cell rounding with IC50 value of 171.8 and 104.3 ppm Wi 38 and Caco-2 cell lines respectively, which revealing the high toxicity of Se-NPs towards cancer cells compared with normal cells. However, Se-NPs displayed larvicidal activity against causative malaria vector Anopheles stephensi.

Boosting the Photocatalytic Hydrogen Evolution Activity for D-π-A Conjugated Microporous Polymers by Statistical Copolymerization.

Abstract: Recently, great progress has been achieved in the design and preparation of conjugated organic polymer photocatalysts for hydrogen generation. However, it is still challenging to develop an organic polymer photocatalyst with high photoconversion efficiency. Rational structure design of organic polymer photocatalysts holds the key point to realize high photocatalytic performance. Herein, a series of donor-π-acceptor (D-π-A) conjugated organic copolymer photocatalysts is developed using statistical copolymerization by tuning the feed molar ratio of pyrene (donor) to dibenzothiophene-S,S-dioxide (acceptor) units. It reveals that the photocatalytic activity of the resulting copolymers is significantly dependent on the molar ratio of donor to acceptor, which efficiently changes the polymer structure and component. When the monomer feed ratio is 25:75, the random copolymer PyBS-3 of 10 mg with Pt cocatalyst shows a high hydrogen evolution rate of 1.05 mmol h-1 under UV/Vis light irradiation using ascorbic acid as the hole-scavenger, and an external quantum efficiency of 29.3% at 420 nm, which represents the state-of-the-art of organic polymer photocatalysts. This work demonstrates that statistical copolymerization is an efficient strategy to optimize the polymer structure for improving the photocatalytic activity of conjugated organic polymer catalysts.

Vitamin C—Sources, Physiological Role, Kinetics, Deficiency, Use, Toxicity, and Determination

Abstract: Vitamin C (L-ascorbic acid) has been known as an antioxidant for most people. However, its physiological role is much larger and encompasses very different processes ranging from facilitation of iron absorption through involvement in hormones and carnitine synthesis for important roles in epigenetic processes. Contrarily, high doses act as a pro-oxidant than an anti-oxidant. This may also be the reason why plasma levels are meticulously regulated on the level of absorption and excretion in the kidney. Interestingly, most cells contain vitamin C in millimolar concentrations, which is much higher than its plasma concentrations, and compared to other vitamins. The role of vitamin C is well demonstrated by miscellaneous symptoms of its absence—scurvy. The only clinically well-documented indication for vitamin C is scurvy. The effects of vitamin C administration on cancer, cardiovascular diseases, and infections are rather minor or even debatable in the general population. Vitamin C is relatively safe, but caution should be given to the administration of high doses, which can cause overt side effects in some susceptible patients (e.g., oxalate renal stones). Lastly, analytical methods for its determination with advantages and pitfalls are also discussed in this review.

Impact of exogenously applied trehalose on leaf biochemistry, achene yield and oil composition of sunflower under drought stress.

Abstract: This study was carried out to assess the influence of trehalose, a non-reducing disaccharide involved in improving plant stress tolerance, on two cultivars (Hysun 33 and FH 598) of sunflower (Helianthus annuus L.) grown under control and drought stress conditions. At pre-flowering stage, varying concentrations (10, 20 and 30 mM) of trehalose were applied to the foliage. Drought stress significantly suppressed the plant growth, total soluble proteins, chlorophyll, achene yield per plant, oil percentage, organic contents, as well as oil palmitic and linoleic acids in both sunflower cultivars. External application of trehalose significantly reduced RMP (relative membrane permeability), and the accumulation of H2 O2 (hydrogen peroxide), while a considerable improvement was recorded in shoot fresh and shoot and root dry weights, total soluble proteins, glycinebetaine, AsA (ascorbic acid), total phenolics, achene yield per plant, oil contents, inorganic and organic contents, and the activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) enzymes under water-limited regimes. The cultivar Hysun 33 was superior to the other cultivar in plant growth, RMP, glycinebetaine, proline, achene yield per plant, oil contents, and palmitic and linoleic acids. Overall, foliar-applied trehalose improved plant growth, oxidative defense system, yield and oil composition of sunflower under drought stress conditions.

Single-Atom Ruthenium Biomimetic Enzyme for Simultaneous Electrochemical Detection of Dopamine and Uric Acid.

Abstract: Single-atom catalysts have attracted numerous attention due to the high utilization of metallic atoms, abundant active sites, and highly catalytic activities. Herein, a single-atom ruthenium biomimetic enzyme (Ru-Ala-C3N4) is prepared by dispersing Ru atoms on a carbon nitride support for the simultaneous electrochemical detection of dopamine (DA) and uric acid (UA), which are coexisting important biological molecules involving in many physiological and pathological aspects. The morphology and elemental states of the single-atom Ru catalyst are studied by transmission electron microscopy, energy dispersive X-ray elemental mapping, high-angle annular dark field-scanning transmission electron microscopy, and high-resolution X-ray photoelectron spectroscopy. Results show that Ru atoms atomically disperse throughout the C3N4 support by Ru-N chemical bonds. The electrochemical characterizations indicate that the Ru-Ala-C3N4 biosensor can simultaneously detect the oxidation of DA and UA with a separation of peak potential of 180 mV with high sensitivity and excellent selectivity. The calibration curves for DA and UA range from 0.06 to 490 and 0.5 to 2135 μM with detection limits of 20 and 170 nM, respectively. Moreover, the biosensor was applied to detect DA and UA in real biological serum samples using the standard addition method with satisfactory results.

The Role of Plant Growth-Promoting Bacteria in Alleviating the Adverse Effects of Drought on Plants

Abstract: Plant growth-promoting bacteria play an essential role in enhancing the physical, chemical and biological characters of soils by facilitating nutrient uptake and water flow, especially under abiotic stress conditions, which are major constrains to agricultural development and production. Drought is one of the most harmful abiotic stress and perhaps the most severe problem facing agricultural sustainability, leading to a severe shortage in crop productivity. Drought affects plant growth by causing hormonal and membrane stability perturbations, nutrient imbalance and physiological disorders. Furthermore, drought causes a remarkable decrease in leaf numbers, relative water content, sugar yield, root yield, chlorophyll a and b and ascorbic acid concentrations. However, the concentrations of total phenolic compounds, electrolyte leakage, lipid peroxidation, amounts of proline, and reactive oxygen species are considerably increased because of drought stress. This negative impact of drought can be eliminated by using plant growth-promoting bacteria (PGPB). Under drought conditions, application of PGPB can improve plant growth by adjusting hormonal balance, maintaining nutrient status and producing plant growth regulators. This role of PGPB positively affects physiological and biochemical characteristics, resulting in increased leaf numbers, sugar yield, relative water content, amounts of photosynthetic pigments and ascorbic acid. Conversely, lipid peroxidation, electrolyte leakage and amounts of proline, total phenolic compounds and reactive oxygen species are decreased under drought in the presence of PGPB. The current review gives an overview on the impact of drought on plants and the pivotal role of PGPB in mitigating the negative effects of drought by enhancing antioxidant defense systems and increasing plant growth and yield to improve sustainable agriculture.

Strawberry-Derived Exosome-Like Nanoparticles Prevent Oxidative Stress in Human Mesenchymal Stromal Cells.

Abstract: Plant-derived exosome-like nanovesicles (EPDENs) have recently been isolated and evaluated as potential bioactive nutraceutical biomolecules. It has been hypothesized that EPDENs may exert their activity on mammalian cells through their specific cargo. In this study, we isolated and purified EPDENs from the strawberry juice of Fragaria x ananassa (cv. Romina), a new cultivar characterized by a high content of anthocyanins, folic acid, flavonols, and vitamin C and an elevated antioxidant capacity. Fragaria-derived EPDENs were purified by a series of centrifugation and filtration steps. EPDENs showed size and morphology similar to mammalian extracellular nanovesicles. The internalization of Fragaria-derived EPDENs by human mesenchymal stromal cells (MSCs) did not negatively affect their viability, and the pretreatment of MSCs with Fragaria-derived EPDENs prevented oxidative stress in a dose-dependent manner. This is possibly due to the presence of vitamin C inside the nanovesicle membrane. The analysis of EPDEN cargo also revealed the presence of small RNAs and miRNAs. These findings suggest that Fragaria-derived EPDENs may be considered nanoshuttles contained in food, with potential health-promoting activity.

Abiotic stress in crop species: improving tolerance by applying plant metabolites

Abstract: Reductions in crop yields brought about by abiotic stress are expected to increase as climate change, and other factors, generate harsher environmental conditions in regions traditionally used for cultivation. Although breeding and genetically modified and edited organisms have generated many varieties with greater abiotic stress tolerance, their practical use depends on lengthy processes, such as biological cycles and legal aspects. On the other hand, a non-genetic approach to improve crop yield in stress conditions involves the exogenous application of natural compounds, including plant metabolites. In this review, we examine the recent literature related to the application of different natural primary (proline, l-tryptophan, glutathione, and citric acid) and secondary (polyols, ascorbic acid, lipoic acid, glycine betaine, α-tocopherol, and melatonin) plant metabolites in improving tolerance to abiotic stress. We focus on drought, saline, heavy metal, and temperature as environmental parameters that are forecast to become more extreme or frequent as the climate continues to alter. The benefits of such applications are often evaluated by measuring their effects on metabolic, biochemical, and morphological parameters in a variety of crop plants, which usually result in improved yields when applied in greenhouse conditions or in the field. As this strategy has proven to be an effective way to raise plant tolerance to abiotic stress, we also discuss the prospect of its widespread implementation in the short term.

Hydroxychloroquine as Postexposure Prophylaxis to Prevent Severe Acute Respiratory Syndrome Coronavirus 2 Infection : A Randomized Trial.

Abstract: BACKGROUND: Effective prevention against coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is currently limited to nonpharmaceutical strategies. Laboratory and observational data suggested that hydroxychloroquine had biological activity against SARS-CoV-2, potentially permitting its use for prevention. OBJECTIVE: To test hydroxychloroquine as postexposure prophylaxis for SARS-CoV-2 infection. DESIGN: Household-randomized, double-blind, controlled trial of hydroxychloroquine postexposure prophylaxis. (ClinicalTrials.gov: NCT04328961). SETTING: National U.S. multicenter study. PARTICIPANTS: Close contacts recently exposed ( 0.20). The frequency of participants experiencing adverse events was higher in the hydroxychloroquine group than the control group (66 [16.2%] versus 46 [10.9%], respectively; P = 0.026). LIMITATION: The delay between exposure, and then baseline testing and the first dose of hydroxychloroquine or ascorbic acid, was a median of 2 days. CONCLUSION: This rigorous randomized controlled trial among persons with recent exposure excluded a clinically meaningful effect of hydroxychloroquine as postexposure prophylaxis to prevent SARS-CoV-2 infection. PRIMARY FUNDING SOURCE: Bill & Melinda Gates Foundation.

Comparative Study of the Antimicrobial Activity of Selenium Nanoparticles With Different Surface Chemistry and Structure.

Abstract: Although selenium nanoparticles (SeNPs) have gained attention in the scientific community mostly through investigation of their anticancer activity, a great potential of this nanomaterial was recognized recently regarding its antimicrobial activity. The particle form, size, and surface chemistry have been recognized as crucial parameters determining the interaction of nanomaterials with biological entities. Furthermore, considering a narrow boundary between beneficial and toxic effects for selenium per se, it is clear that investigations of biomedical applications of SeNPs are very demanding and must be done with great precautions. The goal of this work is to evaluate the effects of SeNPs surface chemistry and structure on antimicrobial activity against several common bacterial strains, including Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Bacillus subtilis (ATCC 6633), and Kocuria rhizophila (ATCC 9341), as well as Escherichia coli (ATCC 8739), Salmonella Abony (NCTC 6017), Klebsiella pneumoniae (NCIMB 9111) and Pseudomonas aeruginosa (ATCC 9027), and the standard yeast strain Candida albicans (ATCC 10231). Three types of SeNPs were synthesized by chemical reduction approach using different stabilizers and reducing agents: (i) bovine serum albumin (BSA) + ascorbic acid, (ii) chitosan + ascorbic acid, and (iii) with glucose. A thorough physicochemical characterization of the obtained SeNPs was performed to determine the effects of varying synthesis parameters on their morphology, size, structure, and surface chemistry. All SeNPs were amorphous, with spherical morphology and size in the range 70-300 nm. However, the SeNPs obtained under different synthesis conditions, i.e. by using different stabilizers as well as reducing agents, exhibited different antimicrobial activity as well as cytotoxicity which are crucial for their applications. In this paper, the antimicrobial screening of the selected systems is presented, which was determined by the broth microdilution method, and inhibitory influence on the production of monomicrobial and dual-species biofilm was evaluated. The potential mechanism of action of different systems is proposed. Additionally, the cytotoxicity of SeNPs was examined on the MRC-5 cell line, in the same concentration interval as for antimicrobial testing. It was shown that formulation SeNPs-BSA expressed a significantly lower cytotoxic effect than the other two formulations.

Ascorbic acid functionalized CdS–ZnO core–shell nanorods with hydrogen spillover for greatly enhanced photocatalytic H2 evolution and outstanding photostability

Abstract: In this work, a new kind of CdS–ZnO core–shell nanorods with controlled ZnO shell are first synthesized by a simple chemical deposition method in aqueous solution. The thickness and distribution of the ZnO shell can be accurately adjusted, and intimate contact interfaces between CdS and ZnO are well constructed. The optimal CSZ0.5 core–shell heterostructure exhibits a photocatalytic H2 evolution rate of 805.5 μmol h−1 without co-catalysts (3 mg of catalyst, equal to 268.5 mmol g−1 h−1), which is 12 and 895 times higher than that of CdS and ZnO, respectively, and is the maximum value among CdS-based photocatalysts under similar experimental conditions. The significant enhancement in the photocatalytic H2 evolution rate can be mainly attributed to three positive factors: the single-crystalline structure of CdS, the Z-scheme mechanism formed between CdS and ZnO, and the introduced ascorbic acid. The first two factors effectively promote the separation and migration of charge carriers, and the latter factor realizes efficient hydrogen spillover for CdS/ZnO to accelerate the photocatalytic hydrogen evolution reaction. In addition, the homogeneous ZnO shell grown on the CdS core efficiently suppresses the photo-corrosion of CdS, which endows CdS/ZnO with outstanding photostability.

A dual-emitting mixed-lanthanide MOF with high water-stability for ratiometric fluorescence sensing of Fe3+ and ascorbic acid

Abstract: Herein, we design and prepare a dual-emitting lanthanide metal–organic framework (Eu0.07Gd0.03-MOF) based on functionalized ligands, which can be developed as a ratiometric sensor. This self-calibrated material not only displays high water stability but also offers a highly sensitive and color change detection of Fe3+ and ascorbic acid at a low limit of detection. Moreover, water stability surveys for Eu0.07Gd0.03-MOF indicate that it maintains structural stability and displays at least 90.4% and 87.5% fluorescence intensity after storage in water for 28 days in water at 70 °C for 6 days, as well as in acidic-basic solutions of broad pH range (3–11) for four days. More importantly, the low concentration range of Fe3+ and ascorbic acid can be estimated by the ratios of ligand-based emission as an internal reference and Eu3+-based emission as the indicator, thus yielding a visually discernible “color-change-recover” effect.

The synthesis of high bright silver nanoclusters with aggregation-induced emission for detection of tetracycline

Abstract: In this study, the silver nanoclusters (Ag NCs) with aggregation-induced emission property were synthesized successfully by reflux method using silver nitrate (AgNO3) as raw material and N-acetyl-L-cysteine (NAC) as the reductant and capped ligand. The synthesis process was simple, environmentally friendly and the process did not require the addition of other surfactants or common reductant such as sodium borohydride, ascorbic acid. The obtained Ag NCs possessed the special Ag(0)@Ag(I)–SR core-shell structure with aggregation-induced emission characteristic. The Ag NCs exhibited strong green luminescence with an optimal emission wavelength of 494 nm, high quantum yield of 0.44, microsecond long life of 11.07 μs and high content of Ag(I) component. In addition, the obtained Ag NCs were used to detect the tetracycline (TC) with the range of linearity from 1.12 μM to 230 μM and a detection limit of 0.47 μM on account of the quenching mechanism of the internal filtration effect (IFE) and the static quenching effect between tetracycline and Ag NCs. The proposed sensing method based on NAC@Ag NCs showed good sensitivity and selectivity for tetracycline, wide range of linearity, low detection limit and strong anti-interference ability. This method had been applied to detect tetracycline concentration reliably and accurately in actual sample milk.

Selenium nanoparticles synthesized using an eco-friendly method: dye decolorization from aqueous solutions, cell viability, antioxidant, and antibacterial effectiveness

Abstract: Selenium nanoparticles (SeNPs) were fabricated using a green microwave technique in the presence of ascorbic acid. The morphological features indicated that the semi-spherical SeNPs with a diameter 8.5–22 nm were configured in agglomerated spherical shapes with diameters around 0.47–0.71 μm. Furthermore, the removal of Fuchsin Basic dye from aqueous solutions was investigated upon variation of concentration of SeNPs. The degradation efficiency achieved 100% for 10 mg of SeNPs after 34 min of visible light irradiation time. The antioxidant activity was tested via DPPH radical scavenging assay and displayed that the highest scavenging capacity (311.1 ± 15.72 mg/g) was achieved by SeNPs at a concentration of 106.25 mg/mL. Otherwise, the cell viability of SeNPs through human fibroblasts cell lines in-vitro was reduced to be 75.1 ± 3.8% with nanoparticle concentration around 500 μg/mL. The antibacterial activity was investigated against gram-negative and gram-positive bacteria such as Escherichia coli (E.coli), Pseudomonas aeruginosa (P. aeruginosa), Klebsiella pneumoniae (K. pneumonia), Staphylococcus aureus (S. aureus), and Bacillus subtilis (B. subtilis) bacteria after one day of exposure. It was illustrated that SeNPs did not display an activity towards Staphylococcus aureus, while it possessed the highest one against Escherichia coli with MBC of 50 ± 1.76 μg/mL compared with 26 ± 0.6 μg/mL for the standard antibiotic. These tremendous properties of SeNPs indicate that manipulating multifunctional nanoparticles for versatile wound and skin treatment applications is highly encouraging.

S defect-rich ultrathin 2D MoS2: the role of S point-defects and S stripping-defects in the removal of Cr(VI) via synergistic adsorption and photocatalysis

Abstract: In the field of photocatalysis, one focus is on high-performance visible light catalysis. For this study, which follows the defect engineering strategy, ultrathin two-dimensional (2D) S defect-rich MoS2 nanosheets were created in situ by ball-milling MoS2 nanosheets with ascorbic acid and then used for the removal of Cr(VI) from wastewater. The results show that ascorbic acid increases both the specific surface area of MoS2 nanosheets and the concentration of S stripping-defects significantly. Of the samples, D-MoS2-3 (i.e., S defect-rich ultrathin 2D MoS2 nanosheets) exhibited the best Cr(VI) adsorption capacity and photocatalytic activity thanks to its large specific surface area and a high concentration of total S defects (18.5%), 311.1% better than for P-MoS2 (i.e., pristine MoS2 nanosheets) (4.5%). The concentration of S point-defects in D-MoS2-3 is only a little greater than in P-MoS2, but the concentration of S stripping-defects is significantly greater. S point-defects at such a high concentration readily act as recombination centers for photogenerated carriers. By contrast, S stripping-defects that lack dangling Mo-S bonds trap photogenerated holes and add to the separation efficiency of photogenerated electron-hole pairs. As a consequence, the photocatalytic performance of D-MoS2-3 in removing Cr(VI) is significantly better. Given this finding, the present study offers a new design pathway and a reference for the practical application of defect engineering to ultrathin 2D materials.

A polypyrrole/GO/ZnO nanocomposite modified pencil graphite electrode for the determination of andrographolide in aqueous samples

Abstract: This paper presents a novel electrochemical sensor based on a pencil graphite electrode (PGE) modified with molecularly imprinted graphene oxide/zinc oxide nanocomposites for a sensitive detection of andrographolide. This is the first report of the novel method of electroanalytical determination of andrographolide through a modified PGE. The modified PGE was successfully fabricated and characterized. Then, quantitative analyses were performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The optimum conditions for this analysis were the supporting electrolyte containing 0.1 M KCl and 0.001 M K3Fe(CN)6, citrate buffer of pH 4, modulation amplitude of 50 mV, and scan rate of 10 mV/s. Under optimized parameters, a good linear response was obtained for andrographolide detection by DPV with a range of 50–145 µM and a detection limit of 42.6 µM. The relative standard deviation (R.S.D.) of the three measurements is 1.47%, which shows the excellent repeatability of the proposed method, while reproducibility analysis produced a R.S.D. value of 4.46%. The proposed technique with optimum conditions exhibited good selectivity towards the detection of andrographolide in the presence of ascorbic acid, uric acid, and cyclodextrin. This method was successfully applied to determine andrographolide in real water samples, and the results are comparable with the established method.

Discrepancies in global vitamin C recommendations: a review of RDA criteria and underlying health perspectives

Abstract: The concept of a 'recommended dietary allowance' (RDA) and similar terms describing the daily intake of essential nutrients recommended for healthy individuals is widely used by various health authorities around the world. For vitamin C, however, there remain significant discrepancies in the criteria used to establish dietary recommendations and consequently, global recommendations for daily vitamin C intake vary by more than five fold. While it appears that the scientific data underlying the recommendations are more or less the same, the interpretation differs considerably. Moreover, although a number of the assumptions used in e.g. the body pool estimates of the 1960s and 1970s have later been proven wrong and give rise to significant underestimations, these data are still used as the main support of several recommendations. Aspects that modify vitamin C requirements, such as gender, age, pregnancy, lactation, and smoking, have been taken into consideration by many but not all regulatory authorities, and are thus subject of debate. In contrast, body weight, a significant predictor of vitamin C status and requirement, has not been taken into consideration with respect to vitamin C recommendations, even in the face of the looming global obesity pandemic. The present review examines the discrepancies in vitamin C dietary recommendations of international authorities and critically discusses representative examples of criteria and the underlying health perspectives used to derive current recommended intakes of vitamin C. New biological signatures of vitamin C nutriture are also explored with regard to their potential use for future updates of dietary recommendations.

Ascorbate oxidation by iron, copper and reactive oxygen species: review, model development, and derivation of key rate constants.

Abstract: Ascorbic acid is among the most abundant antioxidants in the lung, where it likely plays a key role in the mechanism by which particulate air pollution initiates a biological response. Because ascorbic acid is a highly redox active species, it engages in a far more complex web of reactions than a typical organic molecule, reacting with oxidants such as the hydroxyl radical as well as redox-active transition metals such as iron and copper. The literature provides a solid outline for this chemistry, but there are large disagreements about mechanisms, stoichiometries and reaction rates, particularly for the transition metal reactions. Here we synthesize the literature, develop a chemical kinetics model, and use seven sets of laboratory measurements to constrain mechanisms for the iron and copper reactions and derive key rate constants. We find that micromolar concentrations of iron(III) and copper(II) are more important sinks for ascorbic acid (both AH2 and AH-) than reactive oxygen species. The iron and copper reactions are catalytic rather than redox reactions, and have unit stoichiometries: Fe(III)/Cu(II) + AH2/AH- + O2 → Fe(III)/Cu(II) + H2O2 + products. Rate constants are 5.7 × 104 and 4.7 × 104 M-2 s-1 for Fe(III) + AH2/AH- and 7.7 × 104 and 2.8 × 106 M-2 s-1 for Cu(II) + AH2/AH-, respectively.