Epinephrine-sensor

Hsu, C. W., and M. C. Yang, 2008. Electrochemical epinephrine sensor nsing artificial receptor synthesized by sol-gel process. Sens Actual B-Chem 134 680-86. 

By immobilizing Mn(III)-tetrakis(4-sulfonatophenyl)-porphyrin on dioctadecyl-dimethyl ammonium chloride bilayer membranes incorporated into a PVC film, Kuniyoshi et al. [65] developed an epinephrine CL sensor, which allowed determination of epinephrine down to 3 pM with an RSD of 1.0% for 50 pM of this biological compound. Compared with the previously reported epinephrine CL sensor [66], the present authors noted that the alkaline carrier solution, at high concentration levels, caused gradual deterioration of the immobilized catalyst, and this problem could be solved by the use of immobilization techniques other than ion exchange, e.g., solubilization of the catalyst that has octadecyl groups in the bilayer molecules. 

Additional improvements can be achieved through the use of multilayers (based on different overlaid films). Such combination of the properties of different films has been documented with bilayers of Nation/CA (14) and Nafion/collagen (29). The former allows selective measurements of the neurotransmitter dopamine in the presence of the slightly larger epinephrine and the anionic ascorbic acid (Figure 5). In addition to bilayers, mixed (composite) films, such as PVP/CA (75) or polypyrrole/Eastman Kodak AQ (30) layers can offer additional permselectivity advantages, such composites exhibit properties superior to those of their individual components. Also promising are sensor arrays, based on electrodes coated with... 

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. 

Liang CD, Peng H, Zhou AH, Nie LH, Yao SZ (2000) Molecular imprinting polymer coated BAW bio-mimic sensor for direct determination of epinephrine. Anal Chim Act 415(2) 135—141... 

Ethylene glycol dimethacrylate (EDMA)-methacrylic acid (MAA) copolymer-based imprinted polymer particles were mixed with poly(vinyl chloride) in THF, and the solution was then spread on the electrode of the QCM by spin coating. After evaporation of the THF, the polymer particles were immobilized on the surface. A phenobarbital-imprinted QCM sensor prepared in this way worked in ethanol [1], while epinephrine- and caffeine-imprinted QCMs worked in buffer solutions (pH 6.0 and pH 8.0, respectively) [2, 3],... 

Owing to the broad spectrum of substrates for both enzymes, the sensor responds to various catecholamines, aminophenols and ferrocene derivatives. The best sensitivities were obtained for aminophenol and epinephrine where the lower limit of detection is 100 pM. The recycling sensor was used to trace the secretion of catecholamines in cultures of adrenal chromaffin cells. Furthermore both a sandwich assay for IgG and displacement of enzyme labeled cocaine have been indicated by the amplification enzyme sensor. 

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. 

Based on ECL inhibition, DA and epinephrine were separated by CE and indirectly determined. Linear ranges for both analytes were 0.1-10 mM and the detection limits (S/N = 3) were 10 nM for DA and 30 nM for epinephrine [107]. A selective and sensitive sensor based on dual-cloud point extraction (DCPE) and tertiary amine labefing for the quantification of indole-3-acetic acid (lAA) and indole-3-butyric acid (IBA) by CE-ECL has been demonstrated. The detection limits (S/N = 3) were 2.5 and 2.8 nM for lAA and IBA, respectively. The proposed method was applied successfully to the detection of low concentrations of two auxins in acacia tender leaves, buds, and bean sprout [108]. 

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 method is already widely used for obtaining sol-gel electrochemical sensors. Target molecules used include molecules such as the catecholamines, dopamine [251,295], and epinephrine [302], a beta blocker, propranolol [303], and parathion and paraoxon pesticides [304]. Marx and Lion [304] reported that the selectivity for binding of parathion compared to paraoxon increased from 1.7 to 30 by the sol-gel imprinting. The insert of Figure 4.14 shows that paraoxon is merely a thio-parathion that is, the P=S bond in parathion is replaced by a P=0 bond in paraoxon, but this meager difference was sufficient to drive very large molecular selectivity. 

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. 

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