Determination of glucose using a coupled-enzymatic reaction with new fluoride selective optical sensing polymeric film coated in microtiter plate wells

The determination of glucose in beverages is demonstrated using newly developed fluoride selective optical sensing polymeric film that contains aluminum (III) octaethylporphyrin (Al[OEP]) ionophore and the chromoionophore ETH7075 cast at the bottom of wells of a 96-well polypropylene microtiter plate. The method uses a dual enzymatic reaction involving glucose oxidase enzyme (GOD) and horseradish peroxidase (HRP), along with an organofluoro-substrate (4-fluorophenol) as the source of fluoride ions. The concentration of fluoride ions after enzymatic reaction is directly proportional to the glucose level in the sample. The method has a detection limit of 0.8 mmol L⁻¹, a linear range of 0.9-40 mmol L⁻¹ and a sensitivity of 0.125 absorbance/decade of glucose concentration. Glucose levels in several beverage samples determined using the proposed method correlate well with a reference spectrophotometric enzyme method based on detection of hydrogen peroxide using bromopyrogallol red dye (BPR). The new method can also be used to determine H₂O₂ concentrations in the 0.1-50 mmol L⁻¹ range using a single enzymatic reaction involving H₂O₂ oxidation of 4-fluorophenol catalyzed by HRP. The methodology could potentially be used to detect a wide range of substrates for which selective oxidase enzymes exist (to generate H₂O₂), with the high throughput of simple microtiter plate detection scheme.     

A novel potentiometric biosensor for selective L-cysteine determination using L-cysteine-desulfhydrase producing Trichosporon jirovecii yeast cells coupled with sulfide electrode

Trichosporon jirovecii yeast cells are used for the first time as a source of l-cysteine desulfhydrase enzyme (EC 4.4.1.1) and incorporated in a biosensor for determining l-cysteine. The cells are grown under cadmium stress conditions to increase the expression level of the enzyme. The intact cells are immobilized on the membrane of a solid-state Ag₂S electrode to provide a simple l-cysteine responsive biosensor. Upon immersion of the sensor in l-cysteine containing solutions, l-cysteine undergoes enzymatic hydrolysis into pyruvate, ammonia and sulfide ion. The rate of sulfide ion formation is potentiometrically measured as a function of l-cysteine concentration. Under optimized conditions (phosphate buffer pH 7, temperature 37 ± 1 °C and actual weight of immobilized yeast cells 100 mg), a linear relationship between l-cysteine concentration and the initial rate of sulfide liberation (dE/dt) is obtained. The sensor response covers the concentration range of 0.2-150 mg L⁻¹ (1.7-1250 μmol L⁻¹) l-cysteine. Validation of the assay method according to the quality control/quality assurance standards (precision, accuracy, between-day variability, within-day reproducibility, range of measurements and lower limit of detection) reveals remarkable performance characteristics of the proposed biosensor. The sensor is satisfactorily utilized for determination of l-cysteine in some pharmaceutical formulations. The lower limit of detection is ∼1 μmol L⁻¹ and the accuracy and precision of the method are 97.5% and ±1.1%, respectively. Structurally similar sulfur containing compounds such as glutathione, cystine, methionine, and d-cysteine do no interfere.     

Spectrophotometric and spectrofluorimetric methods for the determination of tranexamic acid in pharmaceutical formulation

Two simple and sensitive spectrophotometric and fluorimetric methods for the determination of tranexamic acid in tablets are developed. The methods are based on condensation the primary amino group of tranexamic acid with acetyl acetone and formaldehyde producing a yellow coloured product, which is measured spectrophotometrically at 335 nm or fluorimetrically at 480 nm the colour was stable for at least 1 h. Beer's law was valid within a concentration rang of 0.05-2.0 microg ml-1 spectrophotometrically and 0.05-0.25 microg ml-1 fluorimetrically. All the variables were studied to optimize the reaction conditions. No interference was observed in the presence of common pharmaceutical excipints. The validity of both methods was tested by analyzing tranexamic acid in its pharmaceutical preparations. Good recoveries were obtained and the results were comparable with those obtained by standard method.     

Recycling Chocolate Aluminum Wrapping Foil as to Create Electrochemical Metal Strip Electrodes

The development of low-cost electrode devices from conductive materials has recently attracted considerable attention as a sustainable means to replace the existing commercially available electrodes. In this study, two different electrode surfaces (surfaces 1 and 2, denoted as S1 and S2) were fabricated from chocolate wrapping aluminum foils. Energy dispersive X-Ray (EDX) and field emission scanning electron microscopy (FESEM) were used to investigate the elemental composition and surface morphology of the prepared electrodes. Meanwhile, cyclic voltammetry (CV), chronoamperometry, electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were used to assess the electrical conductivities and the electrochemical activities of the prepared electrodes. It was found that the fabricated electrode strips, particularly the S1 electrode, showed good electrochemical responses and conductivity properties in phosphate buffer (PB) solutions. Interestingly, both of the electrodes can respond to the ruthenium hexamine (Ruhex) redox species. The fundamental results presented from this study indicate that this electrode material can be an inexpensive alternative for the electrode substrate. Overall, our findings indicate that electrodes made from chocolate wrapping materials have promise as electrochemical sensors and can be utilized in various applications.     

The Anti-Inflammatory Effect of a γ-Lactone Isolated from Ostrich Oil of Struthio camelus (Ratite) and Its Formulated Nano-Emulsion in Formalin-Induced Paw Edema

The ostrich oil of Struthio camelus (Ratite) found uses in folk medicine as an anti-inflammatory in eczema and contact dermatitis. The anti-inflammatory effect of a γ-lactone (5-hexyl-3H-furan-2-one) isolated from ostrich oil and its formulated nano-emulsion in formalin-induced paw edema was investigated in this study. Ostrich oil was saponified using a standard procedure; the aqueous residue was fractionated, purified, and characterized as γ-lactone (5-hexyl-3H-furan-2-one) through the interpretation of IR, NMR, and MS analyses. The γ-lactone was formulated as nano-emulsion using methylcellulose (MC) for oral solubilized form. The γ-lactone methylcellulose nanoparticles (γ-lactone-MC-NPs) were characterized for their size, shape, and encapsulation efficiency with a uniform size of 300 nm and 59.9% drug content. The γ-lactone was applied topically, while the formulated nanoparticles (NPs) were administered orally to rats. A non-steroidal anti-inflammatory drug (diclofenac gel) was used as a reference drug for topical use and ibuprofen suspension for oral administration. Edema was measured using the plethysmograph method. Both γ-lactone and γ-lactone-MC-NPs showed reduction of formalin-induced paw edema in rats and proved to be better than the reference drugs; diclofenac gel and ibuprofen emulsion. Histological examination of the skin tissue revealed increased skin thickness with subepidermal edema and mixed inflammatory cellular infiltration, which were significantly reduced by the γ-lactone compared to the positive control (p-value = 0.00013). Diuretic and toxicity studies of oral γ-lactone-MC-NPs were performed. No diuretic activity was observed. However, lethargy, drowsiness, and refusal to feeding observed may limit its oral administration.     

Comparison of the chromatographic behavior of tricyclic neuroleptics on calixarene-bonded, monolithic and conventional RP-HPLC columns

The effect of different chromatographic conditions, such as buffer concentration and type of organic modifier, on the retention behavior of nine tricyclic neuroleptics on three different RP-HPLC columns was investigated. Two recently developed columns, calixarene-bonded (CALTREX) AIII) and monolithic (Chromolith) Performance RP-18e) columns, were compared with a conventional RP-C18 HPLC column (LiChrospher). The results showed how the mobile phase conditions had different effects on the analyte retention on these three columns. For example, the elution order of some analytes and the initiation of separation of the geometric isomers of the three analytes--which have E/Z-isomers (cis/trans-isomers)--could be altered by changing the conditions and the column type. Under identical conditions, a calixarene-bonded phase was the best for this separation, a monolithic phase gave comparable results and the conventional RP-column was the least effective. Concerning the geometric isomers separation, the Chromolith Performance RP-18e was superior.     

Effect of chromatographic conditions on liquid chromatographic chiral separation of terbutaline and salbutamol on Chirobiotic V column

In this study, a method for enantioseparation of terbutaline and salbutamol was established using Chirobiotic V column as a stationary phase. Polar ionic mode applying mobile phase containing ammonium nitrate in 100% ethanol, pH 5.1 was found to give the best separation. The salt concentration in the mobile phase and pH value were found to be the most important chromatographic factors affecting separation. Separation of enantiomers of these two basic analytes was complete in less than 10 min without applying ammonium trifluoroacetate (ATFA) or triethylamine (TEA) salts.     

Nanocomposite solid polymeric electrolyte of 49% poly(methyl methacrylate)-grafted natural rubber�Ctitanium dioxide�Clithium tetrafluoroborate (MG49-TiO2-LiBF4)

A nanocomposite polymer electrolyte consisting of 49% poly(methyl methacrylate)-grafted natural rubber (MG49) as a polymer matrix, lithium tetrafluoroborate (LiBF₄) as a dopant salt, and titanium dioxide (TiO₂) as an inert ceramic filler was prepared by solution casting technique. The ceramic filler, TiO₂, was synthesized in situ by a sol?Cgel process. The ionic conductivity was investigated by alternating current impedance spectroscopy. X-ray diffraction (XRD) was used to determine the structure of the electrolyte, and its morphology was examined by scanning electron microscopy (SEM). The highest conductivity, 1.4?×?10^?5 S cm^?1 was obtained at 30 wt.% of LiBF₄ salt addition with 6 wt.% of TiO₂ filler content. Ionic conductivity was found to increase with the increase of salt concentration. The optimum value of conductivity was found at 6 wt.% of TiO₂. The XRD analysis revealed that the crystalline phase of the polymer host slightly decreased with the addition of salt and filler. The SEM analysis showed that the smoother the surface of the electrolyte, the higher its conductivity.     

Polyamide capsules via soft templating with oil drops—2. Subsequent radical polymerization of styrene

The production of composite polyamide–polystyrene microcapsules by successive polycondensation and radical polymerization is easily possible in a one-pot multi-step reaction. The first step is the emulsification of the template oil phase that contains terephthaloylchloride, styrene monomer, if necessary a cyclohexane–chloroform mixture, and the oil-soluble radical initiator in an aqueous poly(vinyl alcohol) solution. Then, the polyamide capsule formation (second step) is started by the addition of an aqueous diamine solution at 25 °C. Subsequently, the radical polymerization (third step) is initiated by raising the temperature. The morphology of the composite capsules depends strongly on the amount of styrene monomer in the oil mixture and the nature of the initiator. Interestingly, the styrene conversion is much lower if water-soluble initiators are used.