Electrochemical sensor for L-cysteine by using a cobalt(II)/aluminum(III) layered double hydroxide as a nanocatalyst.

A voltammetric sensor is described for the determination of L-cysteine (Cys). A pencil graphite electrode (PCE) was modified with a Co(II)-Al(III) layered double hydroxide (LDH) to obtain a disposable, inexpensive and sensitive sensor for Cys. The LDH was electrochemically deposited on the PGE by chronoamperometry. The electrochemical behavior of the modified PGE was investigated by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry. The structure and morphology of the electrodes surface were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Experiments were conducted in optimal condition, scan rate of 10 mV. s-1 and the oxidation peak potential 0.15 V vs. saturated calomel electrode. The sensor has a linear response in the 100 pM to 0.1 µM Cys concentration range and a 100 pM detection limit. It was used to quantify Cys in a drug sample. Graphical abstract Schematic presentation of pencil graphite electrode modification with Co-Al layered double hydroxide nanaocatalyst by chronoamperometry, and its usage as an electrochemical sensor for L-cysteine determination.

An electrochemical sensor for rizatriptan benzoate determination using Fe3O4 nanoparticle/multiwall carbon nanotube-modified glassy carbon electrode in real samples.

In this paper a sensitive and selective electrochemical sensor for determination of rizatriptan benzoate (RZB) was proposed. A glassy carbon electrode was modified with nanocomposite of multiwalled carbon nanotubes (MWCNTs) and Fe3O4 nanoparticles (Fe3O4/MWCNTs/GCE). The results obtained clearly show that the combination of MWCNTs and Fe3O4 nanoparticles definitely improves the sensitivity of modified electrode to RZB determination. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), square wave voltammetry (SWV) and cyclic voltammetry (CV). Also, the effect of experimental and instrumental parameters on the sensor response was evaluated. The square wave voltammetric response of the electrode to RZB was linear in the range 0.5-100.0 µmol L(-1) with a detection limit of 0.09 µmol L(-1) under the optimum conditions. The investigated method showed good stability, reproducibility and repeatability. The proposed sensor was successfully applied for real life samples of blood serum and RZB determination in pharmaceutical.

Treatment Outcomes and Prognostic Factors in Pediatric Non-brainstem Astrocytoma in North East of Iran.

BACKGROUND: Central Nervous System (CNS) tumors have accounted for approximately one fourth of all pediatric malignancies. CNS tumors have been the most common solid malignancies among the children. In this study, we have evaluated survival and prognostic factors in children with non-brain stem astrocytoma. METHODS: Children with non-brain stem astrocytoma, referring to radiation oncology centers of Ghaem and Omid hospitals of Mashhad, have included in this retrospective study, in years 2000-2010. Patients' demographic data, past medical history, clinical symptoms, extent of tumor resection and treatment modality have recorded. Disease-free survival and overall survival have measured using Kaplan-Meier method. RESULTS: We studied 87 patients with male to female ratio of 44/43 (1.02), and median age of 10 yrs (range: 2-15 yrs). Tumor grade distribution was as follows: grade I: 20 (23%) subjects; grade II: 34 (39.1%) subjects; grade III: 20 (23%) subjects; and grade IV: 13 (14.9%) subjects. The median follow-up duration was 38 months (6 to 110), and 16 months (4 to 100) for patients with low- and high-grade tumors. The 2-year survival rates in grades I-IV were 100%, 84.7%, 60% and 10.8%, respectively. Tumor resection less than gross total and non-ambulation have associated with a significantly inferior survival in both groups multivariate analysis, with high- and low-grade tumors. CONCLUSION: For all the cases of the pediatric non-brainstem astrocytoma, tumor grade had dramatic influences on their survival. Performing gross total resection was crucial for achieving favorable outcomes in both low-grade and high-grade cases. Moreover, according to the results, having major motor deficits has associated with lower survival.