Showing papers by "S. Sriman Narayanan published in 2009"

Catalytic Oxidation of Dopamine at a Nickel Hexacyanoferrate Surface Modified Graphite Wax Composite Electrode Coated with Nafion

Abstract: A chemically modified electrode was successfully fabricated by means of depositing a thin layer of nickel hexacyanoferrate (NiHCF) on an amine adsorbed graphite paraffin wax composite electrode using a new approach. The electrode was further coated with Nafion. The electrochemical characteristics of the modified electrode were studied using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The modified electrode catalyzed dopamine (DA) oxidation in the concentration range of 1.5×10−6 to 1.2×10−3 M without the interference from ascorbic acid (AA). A detection limit of 4.9×10−7 M was obtained for DA in the presence of AA with a correlation coefficient of 0.9972 based on S/N=3. Flow injection analysis was used for the determination of dopamine with excellent reproducible results. The analytical utility of the sensor was evaluated for detection of DA in urine.

Fabrication of an amperometric bienzyme biosensing system with neutral red functionalized carbon nanotubes

Abstract: Novel nanomaterials for biosensor applications represent a rapidly progressing field of nanotechnology. An exploration of functionalized multi-walled carbon nanotubes (MWNTs) as a platform for amperometric determination of glucose employing the enzymes glucose oxidase (GOx) and horseradish peroxidase (HRP), which were immobilized with neutral red (NR) functionalized MWNTs is presented. The fabrication and analytical characterization of the glucose biosensor for the measurement of low concentration of glucose is described. Owing to the electrocatalytic effect of carbon nanotubes, the measurement of faradic responses resulting from enzymatic reactions has been realized at low potential with acceptable sensitivity. Experimental parameters affecting the sensitivity of biosensors, e.g., applied potential, pH, temperature etc., were optimized and potential interferences were examined. The response time for the glucose biosensor was very fast (within 2 seconds) and it showed good storage stability at 4 °C over a 5-month period. The proposed biosensor exhibited short response time, high sensitivity, easy operation, and simple sensor assembly. The biosensor was successfully applied to the determination of glucose in human blood samples and acceptable results were obtained.

Synthesis and in vivo Antidiabetic Activity of Novel Dispiropyrrolidines Through [3 + 2] Cycloaddition Reactions with Thiazolidinedione and Rhodanine Derivatives.

Abstract: The synthesis of a series of novel dispiropyrrolidines has been accomplished by 1,3-dipolar cycloaddition reaction with 5-arylidene-1,3-thiazolidine-2,4-dione and 5-arylidene-4-thioxo-1,3-thiazolidine-2-one derivatives as dipolarophiles. The structure and stereochemistry of the cycloadduct have been established by single crystal X-ray structure and spectroscopic techniques. Molecular docking studies were performed on 1FM9 protein. The synthesized compounds were screened for their antidiabetic activity on male Wistar rats.

Bienzyme based biosensing platform using functionalized carbon nanotubes.

Abstract: This work presents a novel approach to design an amperometric transducer capable of detecting glucose and hydrogen peroxide. The biosensor is based on a bienzyme-channelling configuration, employing the enzymes glucose oxidase and horseradish peroxidase, which were immobilized with Toluidine blue (TB) functionalized multiwalled carbon nanotubes (MWNTs). TB was covalently immobilized with carboxylic acid groups of the carbon nanotubes via carbodiimide reaction. The MWNT/TB/GOD/HRP/Nf nanobiocomposite was prepared by mixing the GOx and HRP solution with TB functionalized CNTs followed by mixing homogeneously with Nafion. The MWNTiTB/GOD/HRP/Nf nanobiocomposite was characterized by scanning electron microscopy. The performance of the MWNT/TB/GOD/HRP/Nf nanobiocomposite modified electrode was examined by electrochemical impedance spectroscopy and cyclic voltammetry. Linear calibrations were achieved upto 1.4 x 10(-7)-1.6 x 10(-3) M for glucose and 6.8 x 10(-8)-1.7 x 10(-3) M for H2O2. A remarkable feature of this bienzyme electrode is the possibility to detect glucose and H2O2 at very low applied potentials where the noise level and interferences from other electro-active compounds are minimal.

(E)-3-Hydr-oxy-13-methyl-16-[4-(methyl-sulfan-yl)benzyl-idene]-7,8,9,11,12,13,15,16-octa-hydro-6H-cyclo-penta-[a]phen-an----thren-17(14H)-one.

Abstract: In the title compound, C26H28O2S, the dihedral angles between the mean plane of the five membered ring and the 4-(methyl­sulfan­yl)benzyl­idine ring in the two crystallographically independent mol­ecules are 34.05 (10) and 40.53 (15)°. The packing is stabilized by inter­molecular O—H⋯O and C—H⋯O inter­actions.

Development and validation of a RP-HPLCmethod for the determination of aztreonamand its related impurities in bulk substances

Abstract: A facile reverse phase high-performance liquid chromatographic method, for the determination of related substances of Aztreonam drug substance has been developed and validated. The degraded products and the isolated impurities were analysed by RP-HPLC utilizing a Octadecylsilane Column (Waters SymmetryC-18, 250i‚´4.6mm, 5i­), followed by ultraviolet detection at 210 nm followed by 254 nm and a mixture of acetonitrile and phosphate buffer 0.02Mwith pH 3.2, used as amobile phase in a gradient elution. This method was validated in terms of Selectivity, Linearity, Precision,Accuracy, Robustness, Limit of detection (LOD), Limit of quantitation (LOQ). This method has been successfully applied for drug substance of Aztreonam.

Synthesis of Highly Substituted Pyrrolidines Through 1,3‐Dipolar Cycloaddition Reaction of N‐Metalated Azomethine Ylides with Triarylideneacetylacetone as Dipolarophile Using Titanocene Dichloride.

Abstract: The 1,3-dipolar cycloaddition reaction of tryarylideneacetyacetone derivatives with N-metalated azomethine ylides in the presence of titanocene dichloride and triethylamine has been investigated. This two-step synthetic sequence is very efficient and yielded the highly substituted pyrrolidines in good yields. The structure and stereochemistry of one of the products has been established by single-crystal x-ray structure and spectroscopic techniques.