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Author(s): V. A. Arlyapov [sup.1], A. S. Khar'kova [sup.1], T. N. Abramova [sup.1], L. S. Kuznetsova [sup.1], A. S. Ilyukhina [sup.1], M. G. Zaitsev [sup.1], A. V. Machulin [sup.2], A. [...], We used conducting redox-active polymers based on chitosan and bovine serum albumin (BSA), covalently bound to mediators ferrocene or Neutral Red, or thionine, modified by carbon nanotubes, as a base of an amperometric biosensor for determining glucose. The structure of the obtained polymers was studied by IR spectroscopy and scanning electron microscopy. Their electrochemical characteristics were studied by cyclic voltammetry. The redox-active polymer based on BSA covalently bound to ferrocene and modified by carboxylated carbon nanotubes demonstrated the most promising characteristics. The biosensor based on the selected hybrid polymer is characterized by high sensitivity, a lower limit of determined concentrations of 0.05 mM, and a high correlation coefficient (R = 0.9919) with the results of determination of glucose in human blood by an alternative method.

In this paper, Au nanoparticles/reduced graphene oxide (AuNPs/rGO) nanocomposites were prepared through a one-pot strategy, carried out by heating the mixture of HAu[Cl.sub.4] and graphene oxide solution at 90°C under alkaline condition. The resultant AuNPs/rGO nanocomposites were found to exhibit good catalytic performance toward [H.sub.2][O.sub.2] reduction and oxidation as well as hydrazine oxidation. The electrochemical sensing application of the nanocomposites for [H.sub.2][O.sub.2], glucose, and hydrazine was also demonstrated successfully. Keywords Au nanoparticles . Reduced graphene oxide . Electrochemical detection . [H.sub.2][O.sub.2] . Glucose . Hydrazine, Introduction Graphene, a two-dimensional aromatic sheets composed of [sp.sup.2]-bonded carbon atoms, has received enormous interest in various areas of research owing to its large specific surface area, excellent thermal and [...]

Addition of carbon (C) and nitrogen (N) to soil can enhance microbial tolerance to salinity, but it is not known if salinity changes the response of microbial activity and biomass to addition of C and N, or how nutrient addition affects microbial tolerance to salinity. We prepared salinity treatments of non-saline soil [electrical conductivity ([EC.sub.1:5]) 0.1 dS [m.sup.-1]] without salt addition or adjusted to four salinity levels (2.5, 5.0, 7.5, 10 dS [m.sup.-1]) using a combination of Ca[Cl.sub.2] and NaCl. The soils were amended with 2.5 mg C [g.sup.-1] as glucose or as mature wheat straw (C/N ratio 47 : 1), with N[H.sub.4]Cl added to glucose to achieve a C/N ratio similar to that of wheat straw, or with N[H.sub.4]Cl added to glucose or wheat straw to achieve a C/N ratio of 20. Soil respiration was measured over 30 days. Microbial biomass C and N (MBC, MBN), dissolved organic C (DOC), and total dissolved N (TDN) were measured on day 30. Cumulative respiration and MBC concentration decreased with increasing EC, less so with glucose than with wheat straw. The MBC concentration was more sensitive to EC than was cumulative respiration, irrespective of C source. Addition of N to glucose and wheat straw to bring the C/N ratio to 20 significantly decreased cumulative respiration and MBC concentration at a given EC. This study showed that in the short term, addition of a readily available and easily decomposable source of energy improves the ability of microbes to tolerate salinity. The results also suggest that in saline soils, irrespective of the C substrate, N addition has no impact, or a negative impact, on microbial activity and growth. Additional keywords: dissolved organic C, microbial activity, microbial biomass, salinity, total dissolved N., Introduction In arid climates, salinity is a major limiting factor for crop production and a contributor to land degradation. Low rainfall and high potential evapotranspiration in these regions promote the [...]

Here, we report on a novel nonenzymatic amperometric glucose sensor based on three-dimensional PtPb networks directly grown on Ti substrates using a reproducible one-step hydrothermal method. The surface morphology and bimetallic composition of the synthesized nanoporous PtPb materials were characterized using scanning electron microscopy and energy-dispersive X-ray spectrometry, respectively. Voltammetry and amperometric methods were used to evaluate the electrocatalytic activities of the synthesized electrodes toward nonenzymatic glucose oxidation in neutral media in the absence and in the presence of chloride ions. The synthesized nanoporous PtPb electrodes have strong and sensitive current responses to glucose. Their amperometric sensitivities increase in the order of Pt-Pb (0%) < Pt-Pb (30%) < Pt-Pb (70%) < Pt-Pb (50%). These nanoporous PtPb electrodes are also highly resistant toward poisoning by chloride ions and capable of sensing glucose amperometrically at a very low potential, -80 mV (Ag/AgCl), where the interference from the oxidation of common interfering species such as ascorbic acid, acetamidophenol, and uric acid is effectively avoided.

The tritium isotope effects to probe the in vitro binding equilibrium between glucose and human brain hexokinase, is utilized. The equilibrium association constant could be increased or decreased by replacing a backbone hydrogen atom in glucose with tritium.

Biocatalytic transformations are exemplified by the electrical contacting of glucose oxidase (GOx) linked to the DNA scaffold with the electrode. Exchanging the positions of a nucleic acid-functionalized microperoxidase-11 (MP-11) and GOx on the DNA scaffold has eliminated the MP-11-electrocatalyzed reduction of [H.sub.2][O.sub.2].

The logic network composed of three enzymes operating in concert as four concatenated logic gates is designed to process four different chemical input signals. The coupling between signal-processing enzyme logic networks and electronic transducers might allow future electronic devices to respond to immediate physiological changes and have provided autonomous signaling/actuation depending on the concentration patterns of the physiological markers.

A platform for photoluminescence (PL) based biosensing is demonstrated for glucose. A compact, potentially miniaturizable sensor is developed that should strongly impact PL-based biosensor technology.