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We present a novel approach for iodide sensing based on the heavy-atom effect to quench the green fluorescent emission of organosilicon nanoparticles (OSiNPs). The fluorescence of OSiNPs was significantly quenched (up to 97.4% quenching efficiency) in the presence of iodide ions (I–) through oxidation by hydrogen peroxide. Therefore, OSiNPs can serve as a fluorescent probe to detect I– with high selectivity and sensitivity. The highly selective response is attributed to the hydrophilic surface enabling good dispersion in aqueous solutions and the lipophilic core allowing the generated liposoluble I2 to approach and quench the fluorescence of OSiNPs. The linear working range for I– was from 0 to 50 μM, with a detection limit of 0.1 μM. We successfully applied this nanosensor to determine iodine content in edible salt. Furthermore, the fluorescent OSiNPs can be utilized for the determination of total antioxidant capacity (TAC). Antioxidants reduce I2 to I–, and the extent of quenching by the remaining I2 on the OSiNPs indicates the TAC level. The responses to ascorbic acid, pyrogallic acid, and glutathione were investigated, and the detection limit for ascorbic acid was as low as 0.03 μM. It was applied to the determination of TAC in ascorbic acid tablets and fruit juices, indicating the potential application of the OSiNP-based I2 sensing technique in the field of food analysis. [ABSTRACT FROM AUTHOR]

Nowadays, nanomaterials enter high numbers of daily used products and drug manufacture. A nanocomposite of vitamins C (VC) and vitamin E (VE) with chitosan as a vehicle and protector was used in a comparative eight-week feeding study, Nile tilapia weighing 31.2 ± 0.36 g distributed in seven groups and fed (G1) basal diet, (G2) bulk VC, (G3) VC- nanoparticles (NPs), (G4) bulk VE, (G5) VE-NPs, bulk VCE (G6), and (G7) VC plus VE (VCE)-NPs, respectively. The Nile tilapia-fed nanocomposite vitamins had significantly higher growth performance compared to the control; VCE-NPs had the superiority among tested supplementations where total weight gain (63.6 g), daily weight gain (1.13 g), relative growth rate (206.1%) with lower feed conversion rate (1.6) and insignificant feed intake (101.5 g). Overall, the level of liver enzymes was significantly decreased in fish serum after eight-week nanocomposite supplementation, and dietary VCE-NPs caused a significant reduction of serum AST (18.45 IU/L) and ALT (14.77 IU/L) compared to the control 25.5 IU/L and 17.6 IU/L, respectively. Fish fed dietary VCE-NPs, VC-NPs, and VE-NPs had significant enhancement of RBCs 4.2 × 106/μL, 3.8 × 106/μL, and 3.55 × 106/μL; WBCs 46.15 × 103, 42.9 × 103, and 44 × 103/μL, respectively, Also TP was significantly higher 6.38 g/dL in VCE-NPs group compared to the control and the other treatments. Over all, the dietary nanocomposite vitamins boost the innate immunity of the experimental Nile tilapia, the oxidative burst activity (OBA), phagocytic activity (PA), phagocytic index (PI), and serum antibacterial (SAA) were significantly increased compared to those received bulk vitamins and the control. The activity of antioxidant biomarkers in fish serum including glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), total antioxidant capacity (TAC), glutathione reductase (GR), and myeloperoxidase (MPO) showed a rise in the serum of Nile tilapia received nano- and bulk-form of VC and VCE compared to the control and both forms of VE. Furthermore, the level of malondialdehyde (MDA), reduced glutathione (GSH), and oxidized glutathione (GSSG) were significantly increased in the fish serum following the trend of antioxidants enzymes. In conclusion, a dietary nanocomposite of vitamin C and vitamin E enhanced Nile tilapia's growth performance and feed utilization. It could also improve health status and immune response. The values of antioxidant biomarkers indicated that the nanocomposite could help the fish body scavenge the generated reactive oxidative species (ROS). [ABSTRACT FROM AUTHOR]

Green fabrication is an environmentally friendly and innovative method, and an attractive research field for the production of magnesium oxide nanoparticles (MgO NPs) in clinical and environmental applications. In this study, a viable green synthetic approach has been carried out to produce MgO NPs by using leaf aqueous extract of Piper nigrum as a capping agent. The formation and physicochemical properties of the MgO NPs were confirmed through standard characterization methods. All the analytical data revealed the formation of pure, rod-shaped, and crystalline MgO NPs with an average size of 20 nm. The low concentration of 50 µg/mL MgO NPs shows 29.99% free radical scavenging, whereas the highest concentration of 500 µg/mL MgO NPs exhibits 91.99% free radical scavenging compared with ascorbic acid. The IC50 of the MgO NPs was found to be 89.5 µg/mL. This study shows that the synthesized MgO NPs exhibit good anti-oxidant activity that can be used for biomedical applications. [ABSTRACT FROM AUTHOR]

Selenium (Se) is a noble mineral that prevents oxidative stress and regulates metabolism by balancing the level of antioxidants in human body. The present work was the first time report of the comparative analysis of bioactivities of selenium nanoparticles (CS-SeNPs and AA-SeNPs) synthesized by Cirsium setidens extracts (CSE) and ascorbic acid (AA), respectively. The CS-SeNPs exhibited an average particle size of 117.8 nm with PDI of 0.162 and zeta potential of − 27.4 mV while average particle size of 108.9 nm with PDI 0.062 and zeta potential of − 32.4 mV for AA-SeNPs. FTIR analysis indicated the surface capping of phyto-compounds of CSE on CS-SeNPs while AA-SeNPs exhibited the functional groups corresponding to AA. The CS-SeNPs exhibited higher DPPH, ABTS, and antibacterial activities than CSE but less than AA-SeNPs. Moreover, both nanoparticles were nontoxic to normal fibroblast cell line (NIH3T3), but cytotoxic to human lung cancer cell line (A549). This work concluded that CS-SeNPs is promising in inhibition of A549 cell line proliferation through damaging the nucleus and mitochondrial membrane. [ABSTRACT FROM AUTHOR]

Selective detection of dopamine is still a challenge due to the strong interference from ascorbic acid (AA). A hybrid dopamine electrochemical sensor was fabricated by boron-doped diamond (BDD) film co-modified with gold nanoparticles and graphite-coated nickel nanoparticles (Au-C@Ni/BDD). Highly sensitive and selective detection toward dopamine was achieved by multiple electrochemical anodic polarization treatment (EAPT) with relatively mild voltage (+ 1.6 V vs. Ag/AgCl) on Au-C@Ni/BDD electrode. Specifically, the oxidation peak separation between ascorbic acid and dopamine reached 166 mV, and the limit of detection of dopamine was as low as 0.015 μM in a linear concentration range of 0.05–100 μM with the sensitivity up to 1.99 μA μM−1 cm−2 even in the presence of interference of high-level AA. These could be ascribed to the electrocatalytically active sites and functional oxygen-containing groups of the hybrid electrodes produced by the EAPT and the excellent catalytical activity of gold nanoparticles. [ABSTRACT FROM AUTHOR]

Minimizing the post-harvest losses in fruits and vegetables is one of the challenging tasks in agriculture. To address this issue, we report nano-net of Cu-chitosan nanoparticles (Cu-chitosan NPs) which has the ability to extend the shelf-life of stored tomato. The application of Cu-chitosan NPs (0.01–0.04%) significantly curtailed microbial decay (< 5 versus > 50% in control), physiological loss in weight (14.36 versus 28.13% in control), respiration rate (0.01173 versus 0.01879 g CO2 kg−1 h−1) and maintained fruit firmness (34.0 versus 17.33 N in control) during storage. Further, these NPs significantly retarded loss of titratable acidity, retained total soluble solids, total and reducing sugars, lycopene, ascorbic acid and inhibited polyphenol oxidase. Likewise, NPs effectively preserved L* (lightness), a* (red/green) and b* (blue/yellow) values and maintained organoleptic score. Scanning electron microscopy study confirmed that Cu-chitosan NPs orchestrate into an invisible-intangible nano-net over tomato surface which may plausibly act as a potential barrier at all possible openings (stem scar, cuticle wax, lenticels, and aquaporins) to control microbial infection, moisture loss, gas exchanges and respiration rate. Overall, nano-net extended keeping quality of tomatoes up to 21 days at room temperature (27 ± 2 °C, 55 ± 2% relative humidity). [ABSTRACT FROM AUTHOR]

In this work, zinc oxide nanoparticles (ZnO-NPs) were synthesized by a chemical precipitation method. A precursor zinc nitrate hexahydrate, polyvinylpyrrolidone (PVP), as a surfactant stabilizing agent and ascorbic acid (AA) as a reducing agent were used. Molar ratios of ascorbic acid to zinc nitrate hexahydrate were changed from 1 to 4 during preparation processes and under the same conditions. Morphology, crystallinity, and particle sizes calculations were studied using Transmission electron microscopy (TEM) and X-ray diffraction. The particle sizes were estimated at 57 nm, 66 nm, 53 nm, 47 nm, and 33 nm and crystalline sizes at 30.05 nm, 26.26 nm, 26.38 nm, 26.53 nm, and 20.80 nm when the ratio of (AA:Zn) was 1, 1.5, 3, 3.5, and 4, respectively. The difference between the particle and crystalline size values because of particle size consist of several crystalline. The results illustrated the effect of different concentrations of (AA:Zn) on the formation and agglomeration of (ZnO - NPs) . Fourier transform infrared spectroscopy results showed that the characteristic transmittance bands of (ZnO - NPs) are closer to 455 c m - 1 . UV - vis spectra results show the absorption band seen at 368 nm , 374 nm , 364 nm , 358 nm , and 352 nm and optical band gap calculated at 3.64 eV , 3.58 eV , 3.70 eV , 3.74 eV , and 3.69 eV when the ratio of (AA:Zn) was 1, 1.5, 3, 3.5, and 4, respectively. These results clarified the effect of quantum sizes effect on the optical band gap of (ZnO - NPs) . [ABSTRACT FROM AUTHOR]

The present study suggested three different highly sensitive luminescent systems based on the employment of silver nanoparticles (NPs), copper oxide nanoparticles and gold nanoparticles in the presence of micellar medium sodium dodecyl sulfate (SDS) for the detection of ascorbic acid in some fruit juices. The fluorescence spectral behavior of ascorbic acid was detected at λem of 420 nm after λex at 350 nm in the presence of acetate buffer (pH 3). Under optimized experimental conditions, the suggested spectroflourimetric systems displayed excellent linearity over concentration ranges of 1.0 × 10–9–1.0 × 10–2, 1.0 × 10–7–1.0 × 10–3 and 1.0 × 10–6–1.0 × 10–3 M with lower limits of detection of 1.0 × 10–10, 5 × 10–8 and 5 × 10–7 M for SDS−AgNPs, SDS−CuONPs and SDS−AuNPs systems, respectively. The suggested approaches were successfully used to detect ascorbic acid in its bulk powder and in some commercial fruit juices. [ABSTRACT FROM AUTHOR]

We proposed a method for the selective and highly sensitive amperometric determination of dopamine and adrenaline in the presence of ascorbic and uric acids in a flow-injection system. Screen-printed electrodes modified with palladium nanoparticles, exhibiting catalytic activity in the electrooxidation of catecholamines, were used as a detector. The difference between the oxidation peak potentials of these compounds is 200 mV. A linear bilogarithmic dependence of the analytical signal on the concentration of dopamine and adrenaline is observed in the ranges from 5 × 10–12 to 5 × 10–8 M and from 1 × 10–9 to 1 × 10–5 M, respectively. For simultaneous two-component analysis, screen-printed electrodes with two working electrodes were used, that is, dual screen-printed electrodes modified with palladium nanoparticles, which enable two substances to be determined simultaneously at two different potentials. The proposed method for the joint flow-injection amperometric determination of dopamine and adrenaline using a modified dual screen-printed electrode was tested in the analysis of urine. [ABSTRACT FROM AUTHOR]

Au/CuO nanoparticles with a size range of 20–40 nm directly synthesized by solution plasma method in water have been successfully applied to the non-enzyme detection of glucose. The electrocatalytic activities of Au/CuO nanoparticles toward glucose were evaluated in an alkaline solution by cyclic voltammetry and real-time current method. Research results demonstrate that the biosensor modified by Au/CuO catalysts has a fast reaction time (< 3 s) and low detection limit (0.22 µM). There are two specific linear ranges of 0.22 µM–1 mM and 3 mM–18 mM, with the sensitivities of 172.45 µA mM−1 cm−2 and 63.66 µA mM−1 cm−2, respectively. Moreover, it also exhibited remarkable current response, good stability (87% after 50 days), superior reproducibility, and excellent selectivity in interfering species (such as D-fructose, ascorbic acid and uric acid). Therefore, the Au/CuO nanoparticles directly synthesized by solution plasma method can be implemented to the enzyme-free detection of glucose. [ABSTRACT FROM AUTHOR]

A highly sensitive enzyme-induced metallization-based electrochemical signal amplification strategy was developed based on the integration of the enzyme-induced metallization reaction, Au nanoparticles (AuNPs)-induced silver deposition, chemically modified electrode and highly sensitive stripping voltammetry detection. The presence of alkaline phosphatase (ALP) catalyzed ascorbic acid 2-phosphate into ascorbic acid, which reduced Ag+ to Ag0 on the surface of the AuNPs/multi-walled carbon nanotubes/polyethyleneimine/glassy carbon electrode (AuNPs/MWNTs/PEI/GCE). As a result, the enzyme-generated product was accumulated on the surface of the AuNPs/MWNTs/PEI/GCE by means of silver deposition via this signal amplification strategy, which enhanced the detection signal dramatically. Amounts as low as 1 × 10–8 U/mL (corresponding to 10 aM) ALP can be detected using this strategy, which is about 4−7 orders of magnitude more sensitive than with other reported methods for ALP determination. In addition, this strategy can be applied to ALP detection in real complex samples, which shows great potential in the early diagnosis of diseases. [ABSTRACT FROM AUTHOR]

The extraction of bimetallic Au-Pt nanoparticles is interesting due to their multiple applications in catalytic processes, electronic devices, photothermal therapies, among others. On the other hand, the tendency of nanoparticles forming agglomerates may modify the behavior of the material, and thus their applications. This study shows a highly reproducible novel synthesis method, which only uses two organic agents (sucrose and ascorbic acid) as the reducing and stabilizing agents from nano-agglomerates of Au-Pt at room temperature. The TEM images show agglomerates with a mass fractal structure. We identified crystalline FCC, corresponding to the Au-Pt alloy. Furthermore, the coexistence of gold and platinum nanoparticles was shown through the EDS analysis. The UV-Vis spectrum showed that the resonance plasmon identified coincides with a great approximation to the results reported in the literature. Additionally, the agglomerates exhibited excellent antibacterial activity against bacteria Escherichia coli. [ABSTRACT FROM AUTHOR]

NiO was synthesized simply via thermal decomposition of nickel ascorbate, which resulted from semi-solid reaction of nickel acetate and ascorbic acid. The prepared precursor was characterized by elemental, thermal and spectral analyses. The precursor was decomposed at 700 °C producing cubic NiO with average size 50 nm as indicated from XRD and TEM. FESEM indicated the formation of macroporous NiO. Magnetic parameters (saturation magnetization (Ms), remanence (Mr) and coercivity (Hc)) of NiO nanoparticles and its precursor were determined and compared with the bulk nickel. Zeta potential measurements at different pH values indicated that NiO is negatively charged. Adsorption of ponceau xylidine dye onto NiO nanoparticles at different parameters as pH, amount of adsorbent and time of adsorption was studied. It was found that the adsorption behavior obeys Langmuir isotherm and intra-particle diffusion model. NiO can remove 97.2% of ponceau xylidine from aqueous media. NiO showed higher adsorption than some other reported adsorbents. In additional to that, the antimicrobial effect of NiO-NPs on Staphylococcus aureus, Candida albicans and Escherichia coli was investigated. NiO nanoparticles exhibited good effects against the tested species. [ABSTRACT FROM AUTHOR]

Application of different surface modified Fe3O4 nanoparticles for enhancing the gel polymers properties and oil recovery increase using gel polymers has been investigated. Fe3O4 Super-paramagnetic nanoparticles were prepared using co-precipitation method, and the surface modified using citric acid, ascorbic acid and tetraethyl orthosilicate (TEOS, SiO2). All the surface modified nanoparticles were super-paramagnetic, considering the vibrating sample magnetometer test results. Adding Fe3O4 and Fe3O4@SiO2 to the gellant samples has resulted in shear viscosity increase of the gel (9.32–9.92 Pa.s and 10.28 Pa.s), but Fe3O4@ascorbic acid has resulted in shear viscosity decrease (8.79 Pa.s) and the gellant sample containing Fe3O4@citric acid did not convert to gel polymer. The samples containing Fe3O4@ascorbic acid synersised after 5–10 days. Nanoparticles has changed the order and constant of the gelation reaction, too. The injection of the gel sample containing 8000 ppm Fe3O4@SiO2 nanoparticles in a heterogeneous micromodel resulted in blocking the high permeability zone and subsequently led to a significant increase in the oil recovery factor from 27.3 to 54%. [ABSTRACT FROM AUTHOR]

We have synthesized NiCo2O4 nanoparticles (NCO NPs) using an ascorbic acid-assisted co-precipitation method for the first time. When NCO NPs are used as an anode material for lithium-ion batteries, the cell exhibits superior lithium storage properties, such as high capacity (700 mA h g−1 after 300 cycles at 200 mA g−1), excellent rate capabilities (applied current density range 100-1200 mA g−1), and impressive cycling stability (at 1200 mA g−1 up to 650 cycles). The enhanced electrochemical properties of NCO NPs are due to the nanometer dimensions which not only offers a smooth charge-transport pathway and short diffusion paths of the lithium ions but also adequate spaces for volume expansion during Li storage. Hence, this eco-friendly synthesis approach will provide a new strategy for the synthesis of various nanostructured metal oxide compounds, for energy conversion and storage systems applications. [ABSTRACT FROM AUTHOR]

A label-free fluorescence assay has been developed for sensitive and selective detection of adenosine triphosphate (ATP) by using poly(thymine) (poly T)-templated copper nanoparticles (CuNPs) as fluorescent indicator. In our design, ATP aptamer was split into two fragments, both of which were elongated with poly T strands that can be utilized as efficient template for the formation of copper nanoparticles through the reduction of copper ions by sodium ascorbate. In the presence of ATP, the two split aptamers could be dragged to form aptamer-ATP aptamer complex, which drew the poly T strands close to each other and induced a remarkable fluorescence enhancement of poly T-templated CuNPs. Thus, an elevated fluorescence enhancement of poly T-templated CuNPs was obtained with the increase in ATP concentration. Under optimized conditions, a good linear range for ATP detection was realized from 100 nM to 100 μM with a detection limit of 10.29 nM. In addition, the application of this biosensing system in complex biological matrix was demonstrated with satisfactory results. This assay provided a simple, label-free, cost-effective, and sensitive platform for the detection of ATP. [ABSTRACT FROM AUTHOR]

The paper covers the research of copper and zinc nanoparticle effect on the content of ascorbic acid, and quantitative and qualitative composition of amino acids and acylcarnitines in Pistia stratiotes L. plants. Plant exposition to copper nanoparticles led to the decrease in (1) the amount of ascorbic acid, (2) the total content of amino acids (by 25 %), and (3) the amount of all studied amino acids except for the glycine amino acid. At this, the amount of 5-oxoproline, arginine, leucine, ornithine, phenylalanine, proline, serine, and tyrosine was two times lower than in control plants. The reduction of the contents of 8 out of 12 investigated acylcarnitines (namely C0, C2, C3, C5, C6, C8, C16, C18:1) was observed in plants under the influence of copper nanoparticles. The result of plants incubation with zinc nanoparticles was the decrease in (1) the amount of ascorbic acid, (2) the total content of amino acids (by 15 %), (3) the content of leucine, methionine, phenylalanine, proline, and tyrosine (more than twice), and (4) the content of 10 acylcarnitines (C0, C2, C3, C4, C5, C10, C16, C18, C18:1, C18:2). The observed reduction in amino acid contents may negatively affect plants adaptive reactions associated with de novo synthesis of stress proteins. At the same time, the decrease in the content of acylcarnitines, responsible for fatty acid transportation, may lead to the changes in the activity and direction of lipid metabolism in plants and reduce plant's ability to use free fatty acids as the oxidation substrate for cell reparation. [ABSTRACT FROM AUTHOR]

Poly (1-amino-2-methyl-9,10-anthraquinone) (PAMAQ) modified electrode (ME) was synthesized at glassy carbon electrode in a binary solvent mixture containing acetonitrile and 5.0 M HSO (1:1) employing a continuous cyclic voltammetry (CV) technique. Nickel (II) nanoparticle ions (NiNPs) were incorporated into the polymer by immersing the ME in an aqueous 1.0 M nickel chloride (NiCl 6HO) solution for 30 min. ME polarization process was performed in an aqueous 0.1 M NaOH solution using CV technique by sweeping the potential between 0.0 and 0.8 V with a potential sweep rate of 0.1 V s for 30 scans to improve its electrochemical response. The obtained NiNPs/PAMAQ-polarized ME was characterized electrochemically using CV technique. The surface morphology of the NiNPs/PAMAQ-polarized ME was analyzed by scanning electron microscopy which demonstrates the presence of NiNPs within the surface of the film. NiNPs/PAMAQ-polarized ME showed excellent catalytic activities toward electrochemical oxidation of ascorbic acid (AA), uric acid (UA), and glucose (Glu) using square-wave voltammetry technique in their single, binary, and ternary mixtures. The ME was applied for the determination of UA, AA, and Glu in real samples. [ABSTRACT FROM AUTHOR]

A ternary composite of hemin, gold nanoparticles and graphene is prepared by a two-step process. Firstly, graphene-hemin composite is synthesized through π-π interaction and then hydrogen tetracholoroauric acid is reduced in situ by ascorbic acid. This ternary composite shows a higher catalytic activity for decomposition of hydrogen peroxide than that of three components alone or the mixture of three components. The Michaelis constant of this composite is 5.82 times lower and the maximal reaction velocity is 1.81 times higher than those of horseradish peroxidase, respectively. This composite also shows lower apparent activation energy than that of other catalysts. The excellently catalytic performance could be attributed to the fast electron transfer on the surface of graphene and the synergistic interaction of three components, which is further confirmed by electrochemical characterization. The ternary composite has been used to determine hydrogen peroxide in three real water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Reduction of the transition metal complexes in aqueous solution has been investigated systematically by ascorbic acid as the reducing agent without the assistance of any surfactant. Nanoparticles of a-Mn2O3, Ag and Cu were synthesized directly through aqueous phase reduction at room temperature. Nanoscale metal oxides such as Co3O4, α-Fe2O3 and MoO2 were obtained through ascorbic acid reduction in alkali medium at 40°C. All the products were characterized on their structure and micro-morphology by the X-ray diffraction (XRD) and atomic force microscopy (AFM). The particle size of metal and metal oxides was about 10-50 nm. The reaction details and features were described and discussed. [ABSTRACT FROM AUTHOR]

Polyaniline films prepared on titanium were employed as substrate for the electrodeposition of gold. The modified electrode was used as anode for the electro-oxidation of ascorbic acid. The electrochemical behavior and electro-catalytic activity of Au/PAni/Ti electrode were characterized by cyclic voltammetry. The morphology of the polyaniline film and gold coating on PAni/Ti electrode were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) techniques, respectively. Results indicated that gold nanoparticles were homogeneously dispersed on the surface of polyaniline film. The electro-oxidation of ascorbic acid is found to proceed more facile on Au/PAni/Ti electrode than on bare gold electrode. The irreversible oxidation current of ascorbic acid exhibits a linear dependence on the ascorbic acid concentration in the range of 1–5 mM. [ABSTRACT FROM AUTHOR]

In this study, well-dispersed gold nanoparticles were prepared by the reduction of HAuCl4 in sodium bis(2-ethylhexyl)sulfosuccinate/isooctane reverse micelles system using ascorbic acid as reducing agent. The properties of the obtained nanoparticles were characterized with transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and UV–vis absorption spectrophotometer. Due to its high water solubility, biodegradability, and low toxicity, ascorbic acid could be used as a benign naturally available reducing agent to synthesize gold nanoparticles. [ABSTRACT FROM AUTHOR]

A drug encapsulation/delivery system using a novel principle is described that is based on an intra-particle migration of calcium ions between a central Ca2+-enriched nanoparticle core and the surrounding shell compartment. The supply of Ca2+ is needed for the formation of a coacervate shell around the nanoparticles, acting as the core of drug-loadable core–shell particles, using the physiological inorganic polymer polyphosphate (polyP). This polyanion has the unique property to form, at an alkaline pH and in the presence of a stoichiometric surplus of calcium ions, water-insoluble and stabile amorphous nanoparticles. At neutral pH a coacervate, the biologically active form of the polymer, is obtained that is composed of polyP and Ca2+. The drug-loaded core–shell particles, built from the Ca–polyP core and the surrounding Ca–polyP shell, were fabricated in two successive steps. First, the formation of the nanoparticle core at pH 10 and a superstoichiometric 2:1 molar ratio between CaCl2 and Na–polyP into which dexamethasone, as a phosphate derivative, was incorporated. Second, the preparation of the coacervate shell, loaded with ascorbic acid, by exposure of the Ca–polyP core to soluble Na–polyP and L-ascorbate (calcium salt). EDX analysis revealed that during this step the Ca2+ ions required for coacervate formation migrate from the Ca–polyP core (with a high Ca:P ratio) to the shell. Electron microscopy of the particles show an electron-dense 150–200 nm sized core surrounded by a less sharply delimited electron-sparse shell. The core–shell particles exhibited strong osteogenic activity in vitro, based on the combined action of polyP and of dexamethasone and ascorbic acid, which reversibly bind to the anionic polyP via ionic Ca2+ bonds. Drug release from the particles occurs after contact with a peptide/protein-containing serum, a process which is almost complete after 10 days and accompanied by the conversion of the nanoparticles into a coacervate. Human osteosarcoma SaOS-2 cells cultivated onto or within an alginate hydrogel matrix showed increased growth/viability and mineralization when the hybrid particles containing dexamethasone and ascorbic acid were embedded in the matrix. The polyP-based core–shell particles have the potential to become a suitable, pH-responsive drug encapsulation/release system, especially for bone, cartilage and wound healing. [ABSTRACT FROM AUTHOR]

A new film containing poly(amido amine) dendrimer, silver nanoparticles and multi-walled carbon nanotubes composite with poly(neutral red) was prepared on a paraffin wax impregnated graphite electrode. The PAMAM / AgNPs–MWCNT / PNR film exhibited promising electrocatalytic oxidation of ascorbic acid (AA) in acetate buffer solution of pH 4.0. The PAMAM / AgNPs–MWCNT / PNR film-modified electrode enhanced the sensitivity of detection of AA. The PAMAM / AgNPs–MWCNT / PNR film-modified electrode was characterized by cyclic voltammetry, chronoamperometry, hydrodynamic voltammetry (HDV) and difference pulse voltammetry. These experiments confirmed the electrocatalytic oxidation of AA by PAMAM / AgNPs–MWCNT / PNR film-modified electrode. The PAMAM / AgNPs–MWCNT / PNR-modified electrode has been found to possess good electrocatalytic activity towards AA oxidation which has been observed at a lower oxidation potential of around 0.26 V with a higher current response. The electrochemical oxidation of AA by PAMAM / AgNPs–MWCNT / PNR-modified electrode involved a two proton and two electron process. A linear relationship between the catalytic current and AA concentration was obtained in the range from 0.16 to 2500 μ M with a detection limit of 0.053 μ M. [ABSTRACT FROM AUTHOR]