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Several new derivatives of 2,2′‐bipyridines with a spacer group separated from the 2,2‐bipyridine fragment, namely, an ethynyl fragment, were obtained using the Sonagashira cross‐coupling reaction. The resulting derivatives were physically adsorbed on platinum electrode and were then used as activators of the catalytic activity of a platinum electrode in the reaction of cholesterol electrooxidation in an acetonitrile medium. Sensitivity, limit of detection and detectable concentration range were calculated, and the best results was established as 6.2±0.6 μA/mM, 0.08 mM and 0–0.3 mM, respectively. These results show that the prepared compounds adsorbed on platinum electrode are perspective systems for developing of new enzymeless cholesterol sensor based on them. [ABSTRACT FROM AUTHOR]

In this work a comparative study of Screen‐Printed Carbon Electrodes (SPCE) – bare and modified by drop casting with carbonaceous nanomaterials (CNMs) as Multi Walled Carbon Nanotubes (MWCNT), Carbon Black and Functionalized Carbon Black for voltammetric determination of 5‐methyl‐6‐nitro‐7‐oxo‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidinide l‐arginine monohydrate (Triazid) as a potential drug with a broad spectrum of antiviral activity is reported. Bare SPCE and CNMs modified SPCE (SPCE/CNMs) have been characterized morphologically by SEM and electrochemically by cyclic voltammetry/electrochemical impedance spectroscopy with [Fe(CN)6]4−/3− as redox probe. Significant improvement of electrochemical performances is achieved with SPCE/CNMs compared with the bare SPCE. Among SPCE/CNMs studied SPCE modified with MWCNT (SPCE/CNT) is characterized by the best combination of electrochemical properties and electroanalytical performance towards TD. The linear dynamic range is 25–200 mg L−1 (R2=0.9975) with the limit of detection – 2.8 mg L−1 Triazid using SPCE/CNT and Square‐Wave Voltammetry technique. The developed sensor was successfully used for Triazid determination in the Pharmaceutical Substance "TRIAZID". The results achieved with SPCE/CNMs after chemical binding of dissolved oxygen in 0.04 M Britton‐Robinson buffer+0.04 M Na2SO3 (pH 7.2±0.2) are very useful for further development of cost‐effective and time‐consuming pharmaceutical routine assay. [ABSTRACT FROM AUTHOR]

Abstract: Biocatalytic cascades involving more than one or two enzyme‐catalyzed step are inefficient inside alginate hydrogel prepared on an electrode surface. The problem originates from slow diffusion of intermediate products through the hydrogel from one enzyme to another. However, enzyme activity can be improved by surface immobilization. We demonstrate that a complex cascade of four consecutive biocatalytic reactions can be designed, with the enzymes immobilized in an LBL‐assembled polymeric layer at the alginate‐modified electrode surface. The product, hydrogen peroxide, then induces dissolution of iron‐cross‐linked alginate, which results in release process of entrapped biomolecular species, here fluorescently marked oligonucleotides, denoted F‐DNA. The enzymatic cascade can be viewed as a biocomputing network of concatenated AND gates, activated by combinations of four chemical input signals, which trigger the release of F‐DNA. The reactions, and diffusion/release processes were investigated by means of theoretical modeling. A bottleneck reaction step associated with one of the enzymes was observed. The developed system provides a model for biochemical actuation triggered by a biocomputing network of reactions. [ABSTRACT FROM AUTHOR]

A convenient synthetic route to novel 7-substituted benzo[ f]thieno[3,2- h]quinazoline and 8-substituted benzo[ g, h]dithieno[2,3- e:3′,2′- j]perimidine systems, bearing the fused pyrimidine ring, has been advanced. A commercially available 5-bromopyrimidine was used as the starting material to obtain various polycyclic systems through the sequence of nucleophilic aromatic substitution of hydrogen (the SNH reaction), Suzuki cross-coupling and oxidative photocyclization. Evidence for the structure of benzo[ g, h]dithieno[2,3- e:3′,2′- j]perimidines has been obtained by X-ray crystallographic analysis. Molecular orbital calculations (DFT), as well as redox and optical measurements for all new compounds have been performed. The data show that the reported polycyclic systems have potential for use in organic electronic applications. [ABSTRACT FROM AUTHOR]