Amperometric Choline Sensor with Enzyme Immobilized by Gamma-Irradiation in a Biocompatible Membrane

Abstract

An amperometric choline biosensor was constructed using choline oxidase immobilized on poly(2-hydroxyethylmethacrylate) membranes obtained by gamma radiation-induced polymerization at low temperature. The measurements were carried out by Clark-type oxygen or hydrogen peroxide electrodes. Calibration curves were linear in the 10-200 umol · 1^?1 range for the oxygen probe and 5-250 umol · 1^?1 for the H₂O₂-based probe. Temperature and pH effects on the activity of immobilized enzyme are described and the response characteristics of the sensor are summarized. The immobilized enzyme membranes stored in glycine buffer or in a dry state were very stable and no significant decrease in the electrode response was observed after three months. The biosensor was employed also to analyse a choline-containing pharmaceutical product and the results were compared to those obtained by enzymatic-spectrophotometric detection.     

Determination of Dopamine Using 2-(4-Boronophenyl)quinoline-4-carboxylic Acids as Fluorescent Probes

The selective identification of dopamine is a significant issue because this compound is an important neurotransmitter closely related to Parkinson’s disease and other mental disorders. 2-(4-Boronophenyl)quinoline-4-carboxylic acid (PBAQA) has been previously reported as a water-soluble fluorescent probe for catechol. However, there are no significant differences in the binding constants between catechol and catecholamines, such as dopamine or levodopa. Here a series of bis-boronic acid compounds based on PBAQA were synthesized and the binding activities were characterized. As a representative compound, the binding constant of 4-(4-((3-(3-borono-4-chlorobenzamido)propyl)carbamoyl)quinolin-2-yl)boronic acid to dopamine is up to 10⁴?L?mol^?1 and much higher than previously reported boronic acid probes. Dopamine selectivity may be achieved by the variation of the substituents in the probe molecules. 4-(4-((3-(3-Borono-4-methoxybenzamido)propyl)carbamoyl)quinolin-2-yl)boronic acid has a stronger binding affinity to dopamine (K_a=5204?±?106?L?mol^?1) than catechol (K_a=2588?±?273?L?mol^?1) or levodopa (K_a=2383?±?273?L?mol^?1). This fluorescence response was used for determining dopamine in a range from 5?×?10^?5?mol?L^?1 to 5?×?10^?4?mol?L^?1 with a detection limit of 7.7?×?10^?6?mol?L^?1. This compound has been successfully used for the assay of dopamine in rabbit plasma, exhibiting excellent specificity. It is believed that synthesized compounds hold great promise as practical platforms to monitor dopamine levels.     

Cobalt(II)-selective membrane electrode based on N,N′-di(thiazol-2-yl)formimidamide

A new PVC-membrane electrode for Co²⁺ ions based on N,N′-di(thiazol-2-yl)formimidamide (TF) as membrane carrier has been developed. The electrode resulted in Nernstian response (29.5?±?0.4?mV decade^?1) for Co²⁺ ion over a wide concentration range (2.5?×?10^?7 ?1.0?×?10^?1?M) with a detection limit of 6.1?×?10^?8?M. The sensor has a response time of about 10?s, and can be used for at least 2 months without observing any deviation from the Nernstain response. The electrode revealed good selectivity towards cobalt(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.0–7.0. The electrode was used for determination of Co²⁺ in real samples.     

Sensitive phenol determination based on co-modifying tyrosinase and palygorskite on glassy carbon electrode

A sensitive tyrosinase biosensor, based on co-modifying tyrosinase and palygorskite on glassy carbon electrode, was developed for phenol analysis. Palygorskite, a kind of natural one-dimensional clay with good biocompatibility, high specific surface area and porous morphology, works as a perfect matrix of enzyme. Tyrosinase retains its inherent bioactivity when immobilized in palygorskite, which leads to a high sensitivity of 1.897 A mol^?1 L. The sensor response achieves 95% of steady-state-current in no more than 3 s, and the linear range of the bioelectrode spans the concentration of phenol from 5?×?10^?8 to 1?×?10^?4 mol L^?1 with a correlation coefficient of 0.9992. The results show no apparent decrease in the response over 2 weeks, and about 80% of the response was retained after 2 months when the electrode was stored at 4–5 °C.     

Determination of Chloride 3-Methyl-9-(2-oxa-2λ5-2H-1,3,2-oxazaphosphorine-2-cyclohexyl)-3,6,9-triazaspiro [5.5] undecane (SLXM-2) in Rats by LC: Application to a Pharmacokinetic Study

A novel and simple liquid chromatographic (LC) method was developed for quantification of a new anticancer compound, chloride 3-methyl-9-(2-oxa-2λ5-2H-1,3,2-oxazaphosphorine-2-cyclohexyl)-3,6,9-triazaspiro [5.5] undecane (SLXM-2) in rat plasma. The present method used protein precipitation for extraction of SLXM-2 from rat plasma. Separation was carried out on a reversed-phase C₁₈ column (150 mm × 4.6 mm i.d., 5 μm). The mobile phases consisted of acetonitrile and 2 mM sodium dodecyl sulfate (SDS) (24:76, v/v). The flow rate was 1.0 mL min^?1. A diode-array detector (DAD) was used and the column effluent was monitored at 192 nm. Regression equations revealed good linear relationship between the peak area and the concentration. The correlation coefficient was 0.9996. The relative standard deviations (RSD) of the precision and accuracy were <9.0% (intra-day) and <6.1% (inter-day), respectively. The recovery and stability were found satisfactory during the study. The method was successfully applied for the pharmacokinetic study of SLXM-2 in rats. After a single dose (400 mg kg^?1) of SLXM-2 was given to rats by intravenous injection, the half-life of SLXM-2 was 0.304 h, the area under the plasma concentration–time curve was 673.1 μg h mL^?1 and the maximal plasma concentration was 1534.9 ± 185.8 μg mL^?1.     

Adsorption voltammetry of the vanadium-2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) system

The behaviour of the vanadium(V) complex with 5-Br-PADAP at a mercury electrode was investigated in HOAcNaOAc. The adsorption phenomena were observed by linear-sweep voltammetry. The mechanism of the electrode reaction was found to be the irreversible reduction of the V(V) in the complex adsorbed on the surface of the electrode to the V(IV) complex with 5-Br-PADAP. In 0.02 mol l^?1 HOAc-0.012 mol l^?1 NaOAc (pH 4.5) and 1 × 10^?6 mol l^?1 5-Br-PADAP, the detection limits of linear-sweep adsorption voltammetry and 1.5th-order derivative adsorption voltammetry are 5 × 10^?10 and 2.5 × 10^?11 mol l^?1 , respectively. The method was applied to samples of ore (Geological Deposit).     

Complex of tris(2-hydroxyethyl)amine with zinc bis(2-methylphenoxyacetate) as an inhibitor of the acid lipase of the aortic intima

The previously unknown ability of Zitrimin, the complex of tris(2-hydroxyethyl)amine with zinc(ii) bis(2-methylphenoxyacetate), to affect the activity of acid lipase of the aortic intima was studied. Daily administration of an aqueous solution of the tris(2-hydroxyethyl)amine complex with zinc bis(2-methylphenoxyacetate) in a dose of 10 mg kg^?1 for 3 months to rabbilts with experimental atherosclerosis was found to decrease the cholesterol and total lipid levels in the aortic tissue and to decrease the degree of aortic damage with atherosclerotic plaques. According to the results of enzymatic analysis, development of atherosclerosis is accompanied by 68% increase in the activity of acid lipase in the intima of the aorta compared to the control.

     

Highly Selective Salicylate Membrane Electrode Based on N,N＇- （Aminoethyl）ethylenediamide Bis（2-salicylideneimine） Binuclear Copper（Ⅱ） Complex as Neutral Carrier

A new ion selective electrode for salicylate based on N,N＇-（aminoethyl）ethylenediamide bis（2-salicylideneimine） binuclear copper（Ⅱ） complex [Cu（Ⅱ）2-AEBS] as an ionophore was developed. The electrode has a linear range from 1.0 × 10^-1 to 5.0 ×10^-7 mol·L^- 1 with a near-Nemstian slope of （ - 55 ±1 ） mV/decade and a detection limit of 2.0 × 10-7 mol·L^-1 in phosphorate buffer solution of pH 5.0 at 25 ℃. It shows good selectivity for Sal^- and displays anti-Hofmeister selectivity sequence： Sal^-〉SCN^-〉 ClO4^- 〉I^-〉 NO2^- 〉Br^-〉 NO3^- 〉Cl^-〉 SO3^2- 〉 SO4^2- The proposed sensor based on binuclear copper（Ⅱ）complex has a fast response time of 5-10 s and can be used for at least 2 months without any major deviation. The response mechanism is discussed in view of the alternating current （AC） impedance technique and the UV-vis spectroscopy technique. The effect of the electrode membrane compositions and the experimental conditions were studied. The electrode has been successfully used for the determination of salicylate ion in drug pharmaceutical preparations.     

Effect of Low‐Level Laser Therapy (660 nm) on Acute Inflammation Induced by Tenotomy of Achilles Tendon in Rats

In this study, we aimed to analyze the effects of low‐level laser therapy (LLLT; 660 nm) on levels of protein expression of inflammatory mediators after cutting Achilles tendon of rats. Thirty Wistar male rats underwent partial incisions of the left Achilles tendon, and were divided into three groups of 10 animals according to the time of euthanasia after injury: 6, 24 and 72 h. Each group was then divided into control group and LLLT group (treated with 100 mW, 3.57 W cm^?2, 0.028 cm², 214 J cm^?2, 6 J, 60 s, single point). In LLLT group, animals were treated once time per day until the time of euthanasia established for each group. The group treated with LLLT showed a significant reduction of IL‐1β compared with control groups at three time points (6 h: P = 0.0401; 24 h: P = 0.0015; 72 h: P = 0.0463). The analysis of IL‐6 showed significant reduction only in the LLLT group at 72 h compared with control group (P = 0.0179), whereas IL‐10 showed a significant increase in the treated group compared with control group at three experimental times (6 h: P = 0.0007; 24 h: P = 0.0256; 72 h: P < 0.0001). We conclude that LLLT is an important modulator of inflammatory cytokines release after injury in Achilles tendon.     

Electrochemical Treatment for Effectively Tuning Thermoelectric Properties of Free‐Standing Poly(3‐methylthiophene) Films

The degree of oxidation of conducting polymers has great influence on their thermoelectric properties. Free‐standing poly(3‐methylthiophene) (P3MeT) films were prepared by electrochemical polymerization in boron trifluoride diethyl etherate, and the fresh films were treated electrochemically with a solution of propylene carbonate/lithium perchlorate as mediator. The conductivity of the resultant P3MeT films depends on the doping level, which is controlled by a constant potential from ?0.5 to 1.4 V. The optimum electrical conductivity (78.9 S cm^?1 at 0.5 V) and a significant increase in the Seebeck coefficient (64.3 μV K^?1 at ?0.5 V) are important for achieving an optimum power factor at an optimal potential. The power factor of electrochemically treated P3MeT films reached its maximum value of 4.03 μW m^?1 K^?2 at 0.5 V. Moreover, after two months, it still exhibited a value of 3.75 μW m^?1 K^?2, and thus was more stable than pristine P3MeT due to exchange of doping ions in films under ambient conditions. This electrochemical treatment is a significant alternative method for optimizing the thermoelectric power factor of conducting polymer films.     

Packed-Bed Reactor Running on Babassu Oil and Glycerol to Produce Monoglycerides by Enzymatic Route using Immobilized Burkholderia cepacia Lipase

The aim of this study was the glycerolysis of babassu oil catalyzed by immobilized lipase from Burkholderia cepacia, in a continuous packed-bed reactor. The best reaction conditions were previously established in batchwise via response surface methodology as a function of glycerol-to-oil molar ratio and reaction temperature. The reactor operated continuously for 22 days at 50 °C, and during the first 6 days, no significant decrease on the initial lipase activity was observed. Monoglycerides concentration was in the range from 25 to 33 wt.%. Subsequently, a progressive decrease in the activity was detected, and an inactivation profile described by Arrhenius model estimated values of 50 days and 1.37?×?10^?2?h^?1, for the half-life and deactivation coefficient, respectively.     

Ionic conductivity in KCl-doped polycrystalline SrCl2

Conductivity studies on polycrystalline SrCl₂ doped with KCl have been carried out. The results are in substantial agreement with published results for single crystal work on SrCl₂, the activation energies being 1.8 eV for the intrinsic region, 0.35 eV for the extrinsic region, and 0.45 eV for the regions in which association of defects occurs. Most significant was the discovery of metastable electrolytes (4–5 mole% KCl in SrCl₂) having a conductivity of 1 × 10^?6 ohm^?1 cm^?1 at room temperature. These supersaturated solutions could be heat cycled up to 72°C, and they retained their initial conductivity after storage for 6 months at room temperature. This indicates that the equilibrium solubility of a dopant is not necessarily the limiting factor for extrinsic conductance in a solid material.     

Field determination of fluoride in drinking water using a polymeric aluminium complex of 5-(2-carboxyphenylazo)-8-hydroxyquinoline impregnated paper

A simple field method which allows the determination of fluoride in drinking water with a small handheld instrument called Arsenator was developed. Arsenator is a commercially available instrument which was used successfully for reliable determination of arsenic. In the proposed method the functionality of the Arsenator which is based on a photometric measurement of a spot on the reagent paper is expanded to analyse fluoride. A polymeric aluminium complex of 5-(2-carboxyphenylazo)-8-hydroxyquinoline (LH₂) has been prepared as a new specific reagent for fluoride. Job's method of continuous variation was adopted for the determination of the composition of the coloured complex, which was further characterized by UV-VIS spectroscopic studies. The molar absorptivity of the complex formation is 8.48?×?10³?L?mol^?1?cm^?1 at 410?nm. The coloured complex reacts with fluoride on an impregnated paper where its colour changes are dependent on the concentration of fluoride in water samples. The change in the colour was measured using the Arsenator. The method allows a reliable determination of fluoride in the range 0.3 to 2.0?mg?L^?1. Further spectophotometric determinations of fluoride in drinking water were also studied. The determination is based on the reaction of aluminium complex with fluoride in the examined samples. Beer's law is obeyed in the range 0.3 to 2.0?mg?L^?1 of fluoride at 495?nm. Sensitivity, detection limit and quantitation limit of the method were found to be 0.251?±?0.007?µg^?1?mL, 0.1?mg?L^?1 and 0.3?mg?L^?1, respectively. The optimum reaction conditions and other analytical conditions were evaluated. The effect of interfering ions on the determination is described. There is no interference by nitrate or chloride. Sulphate interfered only at high concentrations which are not expected in drinking water.     

Microwave Exposure Affecting Reproductive System in Male Rats

The object of present study is to investigate the effects of 50 GHz microwave frequency electromagnetic fields on reproductive system of male rats. Male rats of Wistar strain were used in the study. Animals 60 days old were divided into two groups—group I sham exposed and group II experimental (microwave exposed). During exposure, rats were confined in Plexiglas cages with drilled ventilation holes for 2 h a day for 45 days continuously at a specified specific absorption rate of 8.0 × 10⁻⁴ W/kg. After the last exposure, the rats were sacrificed immediately and sperms were collected. Antioxidant enzyme (superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase), histone kinase, apoptosis, and cell cycle were analyzed in sperm cells. Result shows a significant decrease in the level of sperm GPx and SOD activity (p ≤ 0.05), whereas catalase shows significant increase in exposed group of sperm samples as compared with control (p < 0.02). We observed a statistically significant decrease in mean activity of histone kinase as compared to the control (p < 0.016). The percentage of cells dividing in a spermatogenesis was estimated by analyzing DNA per cell by flow cytometry. The percentage of apoptosis in electromagnetic field exposed group shows increased ratio as compared to sham exposed (p < 0.004). There were no significant differences in the G₀/G₁ phase; however, a significant decrease (p < 0.026) in S phase was obtained. Results also indicate a decrease in percentage of G₂/M transition phase of cell cycle in exposed group as compared to sham exposed (p < 0.019). We conclude that these radiations may have a significant effect on reproductive system of male rats, which may be an indication of male infertility.     

Determination of seven trace elements in natural waters by neutron activation analysis after preconcentration with 1-(2-pyridylazo)-2-naphthol

A procedure is described for the preconcentration of Cd(I), Co(II), Cr(III), Cu(II), Mn(II), U(VI) and Zn(II) from 800 ml of water and sea-water samples by coprecipitation with 1-(2-pyridylazo)-2-naphthol (PAN) prior to neutron activation. Chromium is reduced to Cr(III) by hydroxylammonium chloride at pH 4 before the preconcentration step. Coprecipitation of 30 mg of PAN was most effective at pH 9 with final recoveries of 76–91% for six elements and 50% for uranium. The scheme is based on double irradiation of the same samples. Short (10 min) irradiation followed by γ-spectrometry counting for 10 min gives data for Cd (^111mCd), Co, Cu, Mn and U (²³⁹U). A second 16-h irradiation permits determination of zinc and uranium (²³⁹Np) after a waiting time of 6 h, cadmium (¹¹⁵Cd) after 24 h and chromium after a waiting period of 2 weeks followed by counting for 30 min. Detection limits are 0.04 ng g^?1 for Co, 0.8 ng g^?1 for Cd, 0.3 ng g^?1 for Cu, 0.2 ng g^?1 for Cr, 0.006 ng g^?1 for Mn, 0.006 ng g^?1 for U and 0.3 ng g^?1 for Zn. A further decrease of the detection limit for chromium to 0.05 ng g^?1 can be achieved by separation of interfering nuclides and scintillation counting of ⁵¹Cr with a NaI(Tl) well-type detector.     

Facile Synthesis of Well‐Dispersed Silver Nanoparticles on Hierarchical Flower‐like Ni3Si2O5(OH)4 with a High Catalytic Activity towards 4‐Nitrophenol Reduction

Layered nickel silicate nanoflowers (NSFs) with a hierarchical nanostructure have been successfully fabricated by a template‐free solvothermal method. The as‐prepared nanoflowers were composed of many interconnected edge‐curving lamellae with a thickness of about 15 nm and had a high specific surface area (279 m² g^?1) and large pore volume (0.67 cm³ g^?1). The highly dispersed small silver nanoparticles (AgNPs) were immobilized on the surface of NSFs through the in situ reduction of Ag⁺ by Sn²⁺. The AgNP/NSF nanocomposites showed a high performance in the catalytic reduction of 4‐nitrophenol. In particular, there was no visible decrease in the catalytic activity of the reused catalysts even after being recycled four times. The as‐prepared AgNP/NSF nanocomposites might be an excellent catalyst owing to their availability, formability, chemical and thermal stability, and high specific surface area.     

LC Method for Quantification of Lutein in Rat Plasma: Validation, and Application to a Pharmacokinetic Study

A reversed-phase LC method has been developed for quantitative analysis of lutein in rat plasma and applied to a study of the pharmacokinetics of lutein in rats. From a variety of compounds and solvents tested, astaxanthin was selected as the internal standard. n-Hexane was found to be the best solvent for extracting lutein from plasma. LC analysis of the extracts was performed on a C₁₈ column equipped with a guard pre-column. Linearity was good (r > 0.99) over the range 10–100 ng mL^?1. Recovery from plasma was 82.7–92.9% the intra-day and inter-day precision were always better than 3%. The limits of detection (LOD) and quantification (LOQ) were 2.5 and 8.3 ng mL^?1, respectively. The LC method was used to quantify lutein and zeaxanthin in rat plasma in a 36-h pharmacokinetic study in which experimental rats received a single oral dose of lutein (20 mg kg^?1). The results are presented.     

ELECTRICAL PROPERTIES OF M(S2C2(CN)2)2 1-(M=Ni,Pt) COMPLEXES

Abstract

Single crystal conductivity studies over a temperature range of 200°K to 400°K have been carried out on various M(S₂C₂(CN)₂)₂ ^1-(M=Ni,Pt) salts. A room temperature conductivity of ～ 10^?10ohm^?1 cm^?1 and an E_a?0.5 eV was observed for each of these systems. These results are correlated with the magnetic, electronic, and crystallographic properties. The semiconducting behavior of these systems is related to the electronic structure of the molecular anion.     

Toxicity Test n-Hexane: Ethyl Acetate (3:7) Fraction of Sudamala (Artemisia vulgaris L.)

Sudamala (Artemisia vulgaris L.) is commonly used in the community as anti-tumor in digestive organ, including in oral cavity. However, there have been no scientific studies about oral anti-carcinogenic active substances of Sudamala. The purpose of this study was to analyse the effect of per oral administration of n-hexane: ethyl acetate (3:7) fraction of Artemisia vulgaris L. on healthy mice. This experimental study used male Swiss Webster (Balb C) strain mice (Mus musculus) 2.5 months old, 20-30 grams by weight. Group 1, the mice received 0.5% CMC- Na fraction solvent, as a control. Group 2, the mice received 200 mg/kgbw n-hexane: ethyl acetate (3:7) fraction of Sudamala (Artemisia vulgaris L). The fraction was given once daily for 8 weeks per oral according to the mice's weight. At the end of 8^th week, the mice were killed and oral mucosal tissue was taken for biopsy specimens. Tunnel assay for Apoptosis and immunohistochemistry were undertaken for PCNA. T test analysis showed there was no significant difference between control and treatment groups. The fractions of n-hexane: ethyl acetate (3:7) of Sudamala (Artemisia vulgaris L) was not toxic, it was not harmful to living tissue in healthy mice.     

Synthesis, structure, and electroconductivity of new radical cation salt [Pd(dddt)2]2GaBr4

A new radical cation salt based on the dithiolate complex Pd(dddt)₂ (dddt=5,6-dihydro-1,4-dithiine-2,3-dithiolate) with the tetrahedral anion [GaBr₄]^? was synthesized. The crystal and molecular structure was determined by XRD analysis. The crystal structure of the salt contains Pd(dddt)₂ cation layers alternating with layers of [GaBr₄]^? anions along thec axis of the unit cell. The cation layers contain stacks of Pd(dddt)₂, with a Pd...Pd distance of 3.011 Å. The electroconductivity of [Pd(dddt)₂]₂GaBr₄, single crystals at room temperature is 0.25 Ohm^?1 cm^?1 and decreases with temperature decrease, the activation energy beingE _a=0.66 eV.