Electroanalytical Characterization of Montelukast Sodium and Its Voltammetric Determination in Pharmaceutical Dosage Form and Biological Fluids

The electrochemical properties of montelukast sodium (MKST) at zinc oxide nanoparticles modified carbon paste electrode were investigated by cyclic voltammetry and square wave voltammetry. All studies were based on the irreversible and adsorption-controlled electrochemical reduction signal of montelukast sodium at about -0.7 vs. Ag/AgCl at pH 2.3 in methanol-Britton-Robinson buffer mixture. This adsorptive character of the molecule was used to develop a novel, validated, rapid, selective and simple square wave cathodic adsorptive stripping voltammeric method for the direct determination of montelukast sodium in pharmaceutical and biological fluids without time-consuming steps prior to drug assay. Peak current of electrochemical reduction of montelukast sodium was found to vary linearly with the concentration in the range from 1.0 x 10(-8) to 1.28 x 10(-6) mol L-1. In this method, limit of detection was found to be 7.7 x 10(-9) mol L-1. The method was applied to determine the content of MKST tablet and spiked human serum.Namik Kemal UniversityNamik Kemal University [NKU BAP.00.10.YL.14.03]This work was supported by the Research Fund of the Namik Kemal University. Project No. NKU BAP.00.10.YL.14.03. The authors would like to thank to Prof Esma Kilic for her valuable comments and suggestions on the manuscript

Clinical and Treatment Features of Orbital Neurogenic Tumors

Purpose: To evaluate the clinical and treatment features of orbital neurogenic tumors. Material and Method: The records of 35 patients with orbital neurogenic tumors who were diagnosed and treated at Ankara University Faculty of Medicine, Department of Ophthalmology, between 1998 and 2011 were evaluated retrospectively. Results: Orbitotomy via a cutaneous approach was performed in 21 (60%) cases and orbitotomy via a transconjunctival approach was performed in 7 (20%) cases. Three (8%) cases had been operated at different centers. Four (12%) cases were diagnosed clinically. Total excisional biopsy was performed in 11 (31.4%) cases, subtotal excisional biopsy was performed in 7 (20%), and incisional biopsy was performed in 10 (28.6%) cases. 14 (40%) 35 cases were diagnosed as meningioma, 12 (34%) as peripheral nerve sheath tumor, and 9 (26%) cases were diagnosed as optic nerve glioma. Six (43%) meningioma cases were optic nerve sheath meningioma, 5 (36%) were sphenoid wing meningioma, 2 (14%) were ectopic meningioma, and 1 (7%) was perisellar meningioma. Six (50%) of peripheral nerve sheath tumors were schwannoma, 2 (16%) were solitary neurofibroma, 4 (34%) were plexiform neurofibroma. External beam radiotherapy was performed in 15 (42.8%) cases, cyberknife radiosurgery in 1 (2.8%) , chemotherapy in 1 (2.8%), and enucleation ( because of neovascular glaucoma and vitreous hemorrhage) was performed in 1 (2.8%) case. Discussion: The most common orbital neurogenic tumors are meningioma, peripheral nerve sheath tumor, and optic nerve glioma. For meningioma and glioma, external beam radiotherapy is required; for schwannoma and solitary neurofibroma, total excisional biopsy is the preferred treatment. The success of visual and anatomic results are high after treatment. (Turk J Ophthalmol 2013; 43: 335-9

A Comparison of Four Different Electrode Matrices on the Performance of Amperometric Hydrogen Peroxide (Bio)Sensors

A comparison of the analytical performances of four different (bio)sensor designs in H2O2 determination is discussed. The (bio)sensor designs developed were based on the use of (i) multiwalled carbon nanotubes (MWCNT), zinc oxide nanoparticles (ZnONP), prussian blue (PB); (ii) MWCNT, ZnONP, PB and ionic liquid (IL); (iii) MWCNT, ZnONP and horseradish peroxidase (HRP) and (iv) MWCNT, ZnONP, HRP and IL modified glassy carbon electrode (GCE). A performance comparison of (bio)sensors showed that the one based on HRP/IL-MWCNT-ZnONP/GCE showed the best analytical characteristics with a linear dynamic range of 9.99×10?8–7.55×10?4 M, detection limit of 1.37×10?8 M and sensitivity of 17.00 ?A mM?1. © 2022 Wiley-VCH GmbH19.202, NKUBAP.01This study was supported by Tekirdağ Namık Kemal University Scientific Research Projects Coordination Unit (Project No: NKUBAP.01.GA.19.202)

Ksantin Biyosensörlerin Performansına Çeşitli Çok Duvarlı Karbon Nanotüplerin Etkisi

Bu çalışmada, fonksiyonel grup içermeyen (MWCNT) ve karboksil (COOH-MWCNT), hidroksil (OH-MWCNT) ve amino (NH2-MWCNT) grubu içeren çok duvarlı karbon nanotüplerin amperometrik ksantin biyosensörünün cevabına etkileri incelendi. Bu amaçla, MWCNT’ler ve ksantin oksidaz (XO) enzimi jelatin çözeltisi içinde dağıtıldı ve bu karışımlardan belirli miktarların camsı karbon elektrot yüzeyine damlatılması ile ksantin biyosensörleri hazırlandı. Bu biyosensörlerin optimum pH, enzim miktarı gibi çalışma koşulları belirlendi ve bu koşullarda biyosensörlerin performans faktörleri incelendi. NH2-MWCNT ile hazırlanan biyosensörün en yüksek duyarlık ile ksantine cevap verdiği gözlendi. Bu biyosensör ksantine <15 s gibi kısa bir cevap süresi ile 9,9×10-7 M – 9,4×10-4 M aralığında doğrusal cevap gösterdi ve gözlenebilme sınırı 8,7×10-7 M, duyarlığı 23,36 µA mM-1 olarak belirlendi

Amperometric uric acid biosensor based on poly(vinylferrocene)-gelatin-carboxylated multiwalled carbon nanotube modified glassy carbon electrode

In this study, a new uric acid biosensor was constructed based on ferrocene containing polymer poly (vinylferrocene) (PVF), carboxylated multiwalled carbon nanotubes (c-MWCNT) and gelatin (GEL) modified glassy carbon electrode (GCE). Uricase enzyme (UOx) was immobilized covalently through N-ethyl-N'-(3-dimethyaminopropyl) carbodiimide (EDC) and N-hydroxyl succinimide (NHS) chemistry onto c-MWCNT/GEL/PVF/GCE. The c-MWCNT/GEL/PVF composite was characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Various experimental parameters such as pH, applied potential, enzyme loading, PVF and c-MWCNT concentration were investigated in detail. Under the optimal conditions the dynamic linear range of uric acid was 2.0 x 10(-7) M - 7.1 x 10(-4) M (R=0.9993) with the detection limit low to 2.3 x 10(-8) M. With good selectivity and sensitivity, the biosensor was successfully applied to determine the uric acid in human serum. The results of the biosensor were in good agreement with those obtained from standard method. Therefore, the presented biosensor could be a good promise for practical applications in real samples. (C) 2014 Elsevier B.V. All rights reserved.Ankara University Research FundAnkara University [14L0430005]We gratefully acknowledge the financial support of Ankara University Research Fund (Project No: 14L0430005)

Amperometric Biosensor for Xanthine Determination Based On Fe3O4 Nanoparticles

An amperometric xanthine biosensor was developed based on the immobilization of xanthine oxidase (XO) into the Fe3O4 nanoparticles modified carbon paste. Electron transfer properties of unmodified and Fe3O4 nanoparticles modified carbon paste electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Fe3O4 nanoparticles increased electroactive surface area of the electrode and electron transfer at solution/electrode interface. Optimum pH, nanoparticle loading and enzyme loading were found to be 6.0; 14.2% and 0.6 Unit XO respectively. Fe3O4 nanoparticles modified carbon paste enzyme electrode allowed xanthine determination at -0.20 V, thus minimizing the potential interferences from electrochemically oxidizable substances such as ascorbic acid and uric acid. A linear relationship was obtained in the concentration range from 7.4 x 10(-7) mol L-1 to 7.5 x 10(-5) mol L-1 and a detection limit of 2.0 x 10(-7) mol L-1. The biosensor was used for determination of xanthine in urine samples and the results indicate that the biosensor is effective for the detection of xanthine

Amperometric Biosensors for Tyramine Determination Based on Graphene Oxide and Polyvinylferrocene Modified Screen‐printed Electrodes

A comparison of the analytical characteristics of two tyramine biosensors, based on graphene oxide (GRO) and polyvinylferrocene (PVF) modified screen-printed carbon electrodes (SPCE), is reported. Diamine oxidase (DAOx) or monoamine oxidase (MAOx) was immobilized onto the PVF/GRO modified SPCE to fabricate the biosensors. Surface characteristics and electrochemical behaviour of the modified SPCEs were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and cyclic voltammetry (CV). Electrode surface composition and experimental variables such as pH and working potential were optimized in order to ensure a high performance. Under optimum experimental conditions, both DAOx/PVF/GRO/SPCE and MAOx/PVF/GRO/SPCE biosensors exhibited wide linear dynamic ranges for tyramine from 9.9×10?7 to 1.2×10?4 M and from 9.9×10?7 to 1.1×10?4 M, respectively. MAOx/PVF/GRO/SPCE biosensor showed higher sensitivity (11.98 ?A mM?1) for tyramine determination than the DAOx/PVF/GRO/SPCE biosensor (7.99 ?A mM?1). The substrate specifity of the biosensors to other biogenic amines namely histamine, putrescine, spermine, spermidine, tryptamine, ?-phenylethylamine and cadaverine was also investigated. The developed biosensors were successfully used for tyramine determination in cheese sample. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim116Z159; Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, TÜBITAKThis work was supported by The Scientific and Technical Research Council of Turkey (TUBITAK Project No: 116Z159)

Amperometric Biosensors for Tyramine Determination Based on Graphene Oxide and Polyvinylferrocene Modified Screen-printed Electrodes

A comparison of the analytical characteristics of two tyramine biosensors, based on graphene oxide (GRO) and polyvinylferrocene (PVF) modified screen-printed carbon electrodes (SPCE), is reported. Diamine oxidase (DAOx) or monoamine oxidase (MAOx) was immobilized onto the PVF/GRO modified SPCE to fabricate the biosensors. Surface characteristics and electrochemical behaviour of the modified SPCEs were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and cyclic voltammetry (CV). Electrode surface composition and experimental variables such as pH and working potential were optimized in order to ensure a high performance. Under optimum experimental conditions, both DAOx/PVF/GRO/SPCE and MAOx/PVF/GRO/SPCE biosensors exhibited wide linear dynamic ranges for tyramine from 9.9×10?7 to 1.2×10?4 M and from 9.9×10?7 to 1.1×10?4 M, respectively. MAOx/PVF/GRO/SPCE biosensor showed higher sensitivity (11.98 ?A mM?1) for tyramine determination than the DAOx/PVF/GRO/SPCE biosensor (7.99 ?A mM?1). The substrate specifity of the biosensors to other biogenic amines namely histamine, putrescine, spermine, spermidine, tryptamine, ?-phenylethylamine and cadaverine was also investigated. The developed biosensors were successfully used for tyramine determination in cheese sample. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim116Z159; Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, TÜBITAKThis work was supported by The Scientific and Technical Research Council of Turkey (TUBITAK Project No: 116Z159)

Amperometric Lactate Biosensor Based on Carbon Paste Electrode Modified with Benzo[c]cinnoline and Multiwalled Carbon Nanotubes

Amperometric lactate biosensor based on a carbon paste electrode modified with benzo[c]cinnoline and multiwalled carbon nanotubes is reported. Incorporation of benzo[c] cinnoline acting as a mediator and multiwalled carbon nanotubes providing a conduction pathway to accelerate electron transfer due to their excellent conductivity into carbon paste matrix resulted in a high performance lactate biosensor. The resulting biosensor exhibited a fast response, high selectivity, good repeatability and storage stability. Under the optimal conditions, the enzyme electrode showed the detection limit of 7.0 x 10(-8) M with a linear range of 2.0 x 10(-7) M-1.1 x 10(-4) M. The usefulness of the biosensor was demonstrated in serum samples.Namik Kemal University Research FundNamik Kemal University [NKUBAP.00.10.YL.12.04]; Ankara University Research FundAnkara University [14L0430005]We gratefully acknowledge the financial support of Namik Kemal University Research Fund (Project No: NKUBAP.00.10.YL.12.04) and Ankara University Research Fund (Project No: 14L0430005)

Electrochemical (bio)sensors based on carbon quantum dots, ionic liquid and gold nanoparticles for bisphenol

Electrochemical (bio)sensors were developed for bisphenol A (BPA) determination. Screen printed carbon electrode (SPCE) was modified with ionic liquid 1- butyl-3-methylimidazolium tetrafluoroborate (IL), carbon quantum dots (CQD) and gold nanoparticles (AuNP) for the fabrication of the BPA sensor. Electrode surface composition was optimized for the deposition time of AuNP, amount of CQD and percentage of IL using the central composite design (CCD) method. The results of the CCD study indicated that maximum amperometric response was recorded when 9.8 mu g CQD, 3% IL and 284 s AuNP deposition time were used in modification. Tyrosinase (Ty) was further modified on the AuNP/CQD IL/SPCE to fabricate the biosensor. Analytical performance characteristics of the BPA sensor were investigated by differential pulse anodic adsorptive stripping voltammetry and the AuNP/CQD IL/SPCE sensor exhibited a linear response to BPA in the range of 2.0 x 10(-8) 3.6 x 10(-6) M with a detection limit of 1.1 x 10(-8) M. Amperometric measurements showed that the linear dynamic range and detection limit of the Ty/AuNP/CQD IL/SPCE were 2.0 x 10(-8) - 4.0 x 10(-6) M and 6.2 x 10(-9) M, respectively. Analytical performance characteristics such as sensitivity, reproducibility and selectivity were investigated for the presented (bio)sensors. The analytical applicability of the (bio)sensors to the analysis of BPA in mineral water samples was also tested.Council of Higher Education of Turkey (COHE)Demet Orenli thanks to the Council of Higher Education of Turkey (COHE) for the 100/2000 doctoral scholarship