Norepinephrine sensor

Bearson BL and Bearson SM. 2008. The role of die QseC quorum-sensing sensor kinase in colonization and norepinephrine-enhanced motility of Salmonella enterica serovar Typhimurium. Microb Pathogenesis... 

Presynaptic a2-adrenoceptors function like sensors that enable norepinephrine concentration outside the axolemma to be monitored, thus regulating its release via a local feedback mechanism. When presynaptic a2-re-ceptors are stimulated, further release of norepinephrine is inhibited. Conversely, their blockade leads to uncontrolled release of norepinephrine with an overt enhancement of sympathetic effects at Pi-adrenoceptor-mediated myocardial neuroeffector junctions, resulting in tachycardia and tachyarrhythmia. 

Substantial efforts have been devoted to the development of molecular sensors for dopamine. Raymo et al.70 reported a two-step procedure to coat silica particles with fluorescent 2,7-diazapyrenium dications sensing toward dopamine. The analysis of the fluorescence decay with multiple-equilibria binding model revealed that the electron deficient dications and the electron-rich analytes form 1 1 and 1 2 complexes at the particle/water interface. The interfacial dissociation constants of the 1 1 complexes were 5.6mM and 3.6mM for dopamine and catechol, respectively. Dopamine was dominated by the interaction of its electron-rich dioxyarene fragment with the electron-deficient fluorophore in neutral aqueous environments. Ahn et al.71 reported tripodal oxazoline-based artificial receptors, capable of providing a preorganized hydrophobic environment by rational design, which mimics a hydrophobic pocket predicted for a human D2 receptor. A moderate binding affinity, a dissociation constant of 8.2 mM was obtained by NMR titrations of tripodal oxazoline-based artificial receptor with dopamine in a phosphate buffer solution (pH 7.0). Structurally related ammonium ions, norepinephrine, 2-phenylethylamine,... 

In an attempt to improve the selectivity of local dopamine measurements in the complex extracellular matrix of brain fluid, an implantable enzyme-based dopamine microbiosensor has been constructed based on the immobilization of tyrosinase in a thin-film chitosan coating of carbon-fiber disc microelectrodes [357]. o-Dopaquinone, which is the product of the tyrosinase reaction with dopamine, was monitored via its reduction at the modified microelectrode surface. The application of these cathodic tyrosinase dopamine microbiosensors was reported for the continuous real-time in vivo visualization of electrically stimulated dopamine release in the brain of anesthetized laboratory rats. Remarkably, due to the cathodic potential the sensor response was not significantly disturbed by the presence of typical interferences such as ascorbic and uric acid, serotonin, norepinephrine, and epinephrine. 

Lacc has a broad substrate specificity, it oxidizes a variety of diphenols. Inorganic and organic redox dyes, amino substituted phenols and catecholamines (12). On the other hand GDH accepts a number of redox mediators for glucose oxidation. Therefore, any substrate of Lacc, which oxidized form Is accepted by GDH can be determined by the Lacc-GDH electrode. Consequently, the sensor response is not selective for a certain substrate. However, this is not a problem for the cases described below, when only one of the substrates is present (immunoassays) or a mixture with unchanging ratio of catecholamines (norepinephrine and epinephrine) secretion is analyzed. The dependence of electrode response on the concentration of 8 different substrates is presented In Fig. 3. The optimal substrate is PAP, followed by epinephrine, ferroceneacetic acid, ferrocenecarboxylic acid, L-DOPA, arterenol, 1,1-ferrocendicarboxylic acid, and norepinephrine. It should be noted that for ascorbic acid no amplification was observed. 

Motivated by the high sensitivity for the determination of glucose the same authors performed recent work on the use of low-cost mesoporous carbon inks based on commercial SPE for the amperommetric detection of norepinephrine. The significant effect of this amperommetric sensor was attributed to the use of non-fluorinated based polymeric binders and its extremely high sensitive sensor provoked by the high surface area and pore size of the carbon for the determination of the neuro-transmissor in blood. 

One of the earliest CNT-tipped biological sensor reported was an SWCNT-coated carbon fiber nanoelectrode (100-300 nm tip diameter, as shown in Figure 7.2b). Using cyclic voltammetry, the CNT-tipped electrode could detect dopamine, epinephrine, and norepinephrine at concentrations on an order of magnitude lower than noncoated probes. The demonstration was significant because the dimensions of the CNT-tipped probe would make it possible to study the functions of living cells and tissue with a minimal level of intrusion. Additionally, the pencil-like shape of the probe readily fits the standard ceU physiology equipment and facilitated its use. 

The effects of other neurochemicals on branchial O2 chemoreceptor activity in rainbow trout show similarities and differences to carotid body O2 receptors. Although carotid body chemoreceptors are stimulated by epinephrine and norepinephrine, these neurochemicals appear to have no effect on branchial O2 receptors. Dopamine, the predominant catecholamine in mammalian type 1 cells, also modulates O2 receptor activity in trout gills (15). However, there has been no immimohistochemical demonstration of dopamine in the gills or neuroepithelial cells of fish. These results suggest that the neurotransmitter content of nonmammalian O2 sensors should be examined to determine if there are any phylogenetic trends that may help resolve the functional significance of the various neurotransmitters in O2 chemoreception. 

R.N. Goyal, M.A. Aziz, M. Oyama, S. Chatter] ee, A.R.S. Rana, Nanogold based electrochemical sensor for determination of norepinephrine in biological fluids. Sens. Actuators, B 153 (2011) 232-238. 

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