Development of All‐solid‐state Antidiabetic Drug Metformin‐selective Microsensor and its Electrochemical Applications

In this study, all‐solid‐state type potentiometric PVC membrane selective microsensor was developed for Metformin (MET) which is an antidiabetic drug active substance. Metformin‐tetraphenylborate (MET‐TPB) ion‐pair was used as an ionophore in the structure of the sensor membrane. It was determined that the sensor membrane at the ratio of 69 % o‐nitrophenyl octyl ether, 27 % polyvinyl chloride and 4 % MET‐TPB performed the best potentiometric performance. In a wide concentration range (1×10^?5–1×10^?1 mol/L), the slope, detection limit, response time, pH range, and life‐time of the sensor were determined as 55.9±1.6 mV (R²=0.996), 3.35×10^?6 mol/L, 8–10 s, pH: 3–8, and ～10 weeks, respectively. The voltammetric performances of the sensor were also investigated. The prepared microsensor was successfully utilized for the determination of Metformin in a pharmaceutical drug sample by potentiometry and voltammetry. It was observed that the obtained results were in agreement with the results obtained by the UV spectroscopy method at 95 % confidence level.     

Electrochemical Analysis of Liposome-encapsulated Colistimethate Sodium

In this study, the neutral and cationic liposomal formulations of Colistimethate sodium (CMS), an antibiotic for multi-drug resistant gram-negative bacteria, were prepared and electrochemical quantification of CMS from these liposomes were achieved. This is the first study of the electrochemical detection of CMS released from liposomes. First, the electrochemical properties of CMS were analysed, then the encapsulation efficiency, and the release kinetic of CMS from liposomes were determined with Differential Pulse Voltammetry (DPV) measurements. In addition, Cyclic Voltammetry were applied to determine oxidation signal of CMS. A higher encapsulation efficiency was found in the cationic liposome compared to the neutral liposome. Moreover, CMS was controlled released from liposomes with zero-order drug release kinetics.     

A heat transfer problem with exponential memory and the associated thermal stresses

In this study, a heat transfer problem defined by the Caputo–Fabrizio derivative, which is known to behave by the exponential decaying law, is addressed in an axially symmetric cylindrical region. Thus, the fundamental solutions of the heat diffusion process and the associated thermal stresses are aimed to find. For this purpose, Laplace and finite Hankel integral transforms are applied according to the geometry of the region. To obtain the thermal stresses, constitutive relations of the classical thermoelasticity theory are used. The effects of fractional orders on the diffusion process are illustrated graphically using MATLAB.     

Representations of Clifford Algebras on Function Spaces on the Cantor Set

We give a representation of the (infinite-dimensional) complex Clifford algebra on the Hilbert space of square-integrable complexvalued functions on the Cantor set.     

Design,Synthesis, and Evaluation of Novel 2H-Benzo[b][1,4]thiazin-3(4H)-one Derivatives as New Acetylcholinesterase Inhibitors

Alzheimer’s disease (AD) is a slowly progressive neurodegenerative disease that causes dementia in people aged 65 and over. In the present study, a series of thiadiazole hybrid compounds with benzothiazine derivatives as acetylcholinesterase inhibitors were developed and evaluated for their biological activity. The AChE and BChE inhibition potentials of all compounds were evaluated by using the in vitro Ellman method. The biological evaluation showed that compounds 3i and 3j displayed significant inhibitory activity against AChE. Compounds 3i and 3j showed IC₅₀ values of 0.027 µM and 0.025 µM against AChE, respectively. The reference drug donepezil (IC₅₀ = 0.021 µM) also showed significant inhibition against AChE. Further docking simulation also revealed that these compounds (3i and 3j) interacted with the active site of the enzyme similarly to donepezil. The antioxidant study revealed that compounds 3i and 3j exhibited greater antioxidant effects. An in vitro blood–brain barrier permeability study showed that compounds 3i and 3j are promising compounds against AD. The cytotoxicity study of compounds 3i and 3j showed non-cytotoxic with an IC₅₀ value of 98.29 ± 3.98 µM and 159.68 ± 5.53 µM against NIH/3T3 cells, respectively.     

Fibroin nanofibers production by electrospinning method

Silk fibroin, which has many characteristic properties such as low inflammation reaction, biodegradation, suppleness, good antithrombogenic details, biocompatibility and high tensile strength is a very good candidate for biomedical applications. Electrospinning procures high surface area, porous, nanofiber dimension fiber generation, which is a plain method. An experimental study was carried out to produce nanofiber structure from silk fibroin by electrospinning and the electrospinning parameters for the spinning of uniform, continuous and silk fibroin fibers were optimized. As a result, the effect of variables of concentration, distance and applied voltage on the strength, thickness, surface structure, fiber diameter of nanomaterial was investigated. Then, in vitro cell viability of the silk fibroin mat was analyzed. It was seen that the strength, mat thickness, and fiber diameter increased with solution concentration rise. It was found that the values of the fiber diameter and tensile strength decreased with increasing distance. It was determined that the effect of distance varies depending on the concentration in the mat thicknesses. The tensile strength was affected inversely proportional the applied voltage rises and distance. It was found that the fiber diameter values decreased together with increasing applied voltage. At cell viability of silk fibroin mat was occurred high cell viability after 24 h, but it was obtained low cell viability at the 48th h.     

Solid-Phase Extraction and Spectrophotometric Determination of Trace Amounts of Mercury in Natural Samples

A sensitive and selective solid phase spectrophotometric method for the determination of trace amounts of inorganic mercury is described. Hg²⁺ was sorbed on a silica gel-packed column as an Hg²⁺–N,N-bis(2-mercaptophenyl)ethanediamide (H₂L) complex. The Hg²⁺ complex was eluted from the column using 7mL of acetone. Various parameters including pH, column flow rate, and ligand concentration were optimized. The complex was found to obey Beers law from 2.3 to 73.7µgmL^–1 within the optimum range when the preconcentration factor was two. The effective molar absorption coefficient at 523nm was 1.17×10³Lmol^–1cm^–1 at 523nm. The concentration limits in Beers law dropped from 0.09 to 2.95µgmL^–1 within the optimum range when the preconcentration factor was 50. The relative standard deviation at a concentration level of 5µgmL^–1 Hg²⁺ (9 repetitive determinations) was 1.6%. The detection limits are 0.34µgmL^–1 and 0.015µgmL^–1 when the preconcentration factors are 2 and 50, respectively. The method has been used for routine determination of trace levels of Hg²⁺ in natural waters. The potential application of this method for the removal of Hg²⁺ from natural samples (sea water and lake water) spiked with 100ngmL^–1 of Hg²⁺ was studied. In order to validate the proposed method, LGC 6156 (harbour sediment – extractable metals) was analysed by this method. The results proved that excellent extraction of Hg²⁺ from both natural water samples was obtained by solid phase extraction using N,N-bis(2-mercaptophenyl) ethanediamide.     

Magnetic and dielectric properties of Mn<Subscript>0.2</Subscript>Ni<Subscript>0.8</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles synthesized by PEG-assisted hydrothermal method

We present a systematic investigation on the structural and magnetic properties of Mn_0.2Ni_0.8Fe₂O₄ nanoparticles synthesized by a polyethylene glycol (PEG)-assisted hydrothermal route. XRD, FT-IR, TEM and VSM were used for the structural, morphological, dielectric properties and magnetic investigation of the products, respectively. Average crystallite size of product was estimated using Line profile fitting as 6 ± 1 nm and particle size as 6.5 ± 1.0 nm from TEM micrographs. Magnetization measurements have shown that the particles have a blocking temperature of 134 K. Magnetization and the coercive field of the sample increase by decreasing the temperature. The conductivity measurements reveal the semiconducting behaviour for the sample. Temperature-dependent dielectric properties: dielectric permittivity (ε) and ac conductivity (σ_ac) for the sample were studied as a function of applied frequency in the range from 1 Hz to 3 MHz. These studies indicated that the dielectric dispersion curve for the sample showed usual dielectric dispersion which can be explained on the basis of Koop’s theory, which is based on the Maxwell–Wagner model for the interfacial polarization of homogeneous double structure.     

Determination of rare earth elements in seawater by inductively coupled plasma mass spectrometry with off-line column preconcentration using 2,6-diacetylpyridine functionalized Amberlite XAD-4

An off-line column preconcentration technique using a micro-column of 2,6 diacetylpyridine functionalized Amberlite XAD-4 with inductively coupled plasma mass spectrometry (ICP-MS) as a means of detection has been developed. The aim of the method was to determine rare earth elements (REEs) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) in seawater. Sample solutions (2–10 mL) were passed through the column which was then washed with ultra-pure water to remove residual matrix. The adsorbed cations on the resin were eluted by using 2 mL of 0.1 mol L⁻¹ HNO₃ containing 10 ng mL⁻¹ indium as an internal standard. The eluent was analyzed for the metal concentrations using ICP-MS. Sample pH as well as the sample and eluent flow rates were optimized. The sorption capacity of resin was determined by the batch process, by equilibrating 0.05 g of the resin with solutions of 50 mL of 25 mg L⁻¹ of individual metal ions for 4 h at pH 6.0 at 26 °C. The sorption capacities for the resin were found to range between 47.3 μmol g⁻¹ (for Lu) and 136.7 μmol g⁻¹ (for Gd). Limits of detection (3σ), without any preconcentration, ranged from 2 ng L⁻¹ to 10.3 ng L⁻¹ (for Tm and Lu respectively). The proposed method was applied to the determination of REEs in seawater and tap water samples.     

A simple spectrophotometric procedure for determination of valaciclovir in dosage forms and biological fluids

A simple and selective spectrophotometric procedure for the determination of Valaciclovir (VALA) is proposed and applied to determine the substance in tablets and biological fluids. This procedure is proposed for the determination of VALA in Britton-Robinson (BR) buffer at pH 6.0, which allows quantification over the 4 × 10^?6 to 6 × 10^?5 M range for spectrophotometric measurements. The repeatability and reproducibilty of the procedure for serum and breast milk samples are estimated. Precision and accuracy are also checked. The standard additions method is used for biological fluids. The proposed produce was verified for the determination of VALA in real human serum, breast milk samples; the selectivity over the metabolites was found to be quite satisfactory.