Dopamine detection selectivity

An imprinted poly[tetra(o-aminophenyl)porphyrin] film, deposited on a carbon fibre microelectrode by electropolymerization, was used for selective determination of dopamine [208] in the potential range of —0.15 to 1.0 V. This chemosensor has been used successfully for dopamine determination in brain tissue samples. The dopamine linear concentration range extended from 10 6 to 10-4 M with LOD of 0.3 pM. However, this LOD value is very high compared to that of the dopamine voltammetric detection using polyaminophenol MIPs prepared by electropolymerization [209]. Dopamine was determined by CV and DPV at concentrations ranging from 2 x 10 s to 0.25 x 10 6 M with LOD of 1.98 nM. This LOD value is lower than that of PM dopamine detection [133]. 

Zen, J.-M., and Chen, P.-J. 1997. A selective voltammetric method for uric acid and dopamine detection using clay-modified electrodes. Analytical Chemistry 69, 5087-5093. 

The ability of binaphthyl crown ethers such as (R)-74 to bind to various cations has been extensively studied by Cram et al. [18,62]. Optically active binaphthyl crown ethers have been used to resolve racemic amino ester salts. A racemic 74 has been polymerized on a platinum electrode to prepare a sensor to detect selectively dopamines, important neural transmitters [63,64]. However, because of the... 

Film devices are often developed based on polymer backbone or framework. For example, a poly-pyrrole film with borane in the backbone has been obtained by direct electropolymerisation. Boronic acid derivatised pyrroles have been employed to make molecular imprinted polymers (MIPs), for example for the detection of dopamine. Figure 8.8 shows the concept of polymer formation in the presence of analyte followed by extraction to provide highly selective pockets for dopamine to bind. The read-out in this case is based on the Fe(CN)/" redox probe. Poly-amino-boronic acid films without imprinting were employed for dopamine detection. Co-polymer sensor films based on poly(aniline-co-3-aminobenzeneboronic acid) and poly(acrylamidophenylboronic acid) have been reported. 

Fig. 6 Schematic illustration of the preparation and sensing of the aptasenstn-. Graphene oxide and EDOT was electrochemically deposited onto a glassy carbon electrode to form a composite of PEDOT/GO, and it was further electrochemically reduced to PEDOTriGO (carboxyl group of rGO was retained) Aptamer functionalized with amine group was attached to the PEDOT/rGO nanocomposite film through the reaction between the amine and carboxyl groups Dopamine was selectively captured by the aptamer, and the collected dopamine was then electrochemically detected (Reprinted from Ref. [98] with permission from Springer)...

Describe the rationale of using electrodes coated with Nation films for selective detection of the cationic neurotransmitter dopamine in the presence of the common interference from anionic ascorbic acid. 

The best studied of the endocarmabinoids are anandamide (A -arachidonyl-ethanolamine, AEA)(1) and 2-arachidonylglycerol (2-AG)(2). Anandamide was first identified from porcine brain extracts by Devane and co-workers in 1992 [13], while 2-AG was first reported in 1995 to have been isolated from canine gut [14] and rat brain [15]. More recently, noladin ether (2-arachidonyl-glyceryl ether, 2-AGE)(3) [16], virodhamine (D-arachidonyl-ethanolamine)(4) [17] and A-arachidonyl-dopamine (NADA)(5) [18] were proposed as endogenous ligands for the cannabinoid receptors. In a subsequent publication, the authors failed to detect noladin ether in mammalian brains and questioned the relevance of this compound as an endocarmabinoid [19]. Anandamide, noladin ether and NADA have functional selectivity for CBi receptors, virodhamine is CB2 selective and 2-AG is essentially non-selective. 

Figure 15.14 illustrates a typical voltammetric result for the determination of dopamine in the presence of ascorbic acid with a CNT-modified electrode. The selective voltammetric detection of uric acid [82] or norepinephrine [83] in the presence of ascorbic acid has been demonstrated with a (3-cyclodextrin-modified electrodes incorporating CNTs. Ye et al. [84] have studied the electrocatalytic oxidation of uric acid and ascorbic acid at a well-aligned CNT electrode, which can be used for the selective determination of uric acid in the presence of ascorbic acid. The simultaneous determination of dopamine and serotonin on a CNT-modified GC electrode has also been described [85],... 

Research into chemically modified electrodes has led to a number of new ways to build chemical selectivity into films that can be coated onto electrode surfaces. Perhaps the simplest example is the use of the polymer Nafion (see Table 13.2) to make selective electrodes for basic research in neurophysiology [88]. Starting with the pioneering investigations by Ralph Adams, electrochemists have become interested in the electrochemical detection of a class of amine-based neurotransmitters in living organisms. The quintessential example of this class of neurotransmitters is the molecule dopamine, which can be electrochemically oxidized via the following redox reaction ... 

SV detection was also achieved to detect catecholamines on a PDMS-quartz chip. Pyrolyzed photoresist films (PPF) were used as planar carbon electrodes. Since the photoresist (AZ4330) must adhere on a substrate for pyrolysis at 1000°C, a quartz plate that could withstand high temperature was selected. The LOD of dopamine decreased from 160 nM to 100 nM when the PPF was treated by piranha solution (HjSOyHjOj). It was because such a treatment increased the surface oxygen/carbon ratio, and hence the oxidation kinetics of dopamine wave improved [765]. 

In addition, the selectivity of SV detection can be enhanced by using appropriate harmonics (see Figure 7.25). When the excitation offset was centered on the half-wave potential of dopamine (134 mV vs. silver/AgCl), dopamine was... 

FIGURE 7.25 Manipulation of the applied potential window to enhance selectivity of SV detection. Separation of 5 lM dopamine and 5 pM isoproterenol produced a resolution of 0.9. A 3-Hz sine wave with a 500-mV amplitude with a variable offset was applied for S V detection. 1. Excitation offset centered on the half-wave potential of isoproterenol (180 mV vs. silver/AgCl). (a) First harmonic (3 Hz) time course and (b) fourth harmonic (12 Hz) time course. 2. Excitation offset centered on the half-wave potential of dopamine (134 mV vs. Ag/AgCI). (c) Third harmonic (9 Hz) time course and (d) second harmonic (6 Hz) time course [765]. Reprinted with permission from the American Chemical Society. 

An example of the selectivity of diamond electrodes is the detection of dopamine in the presence of 1000-fold excess of ascorbic acid (typical of the composition of neural extracellular fluid). On an H-terminated diamond, potentials of the dopamine (DA) and ascorbic acid (AA) oxidation peaks on potentiodynamic curves are very close each other the peaks cannot be resolved (Fig. 32). To impart selectivity to diamond electrode, it was subjected to anodic pre-treatment (discussed in Section 6.2). The treated electrode exhibited a substantial shift in the positive direction for the peak potential for AA oxidation, thus making it possible to discriminate between the DA... 

Wu H-P, Cheng T-L, Tseng W-L. Phosphate-Modified Ti02 nanoparticles for selective detection of dopamine, levodopa, adrenahne, and catechol based on fluorescence quenching. Langmuir 2007 23 7880-5. 

Greg Gerhardt pioneered a chronoamperometry method that has been used to observe diffusion and uptake parameters in the rat brain (45). In this technique an exogenous neurotransmitter, such as dopamine, is introduced into the brain by pressure ejection or iontophoresis. The microelectrode is a known distance from the ejection pipette, so the analyte concentration detected at the microelectrode is a function of extracellular diffusion and uptake by the dopamine transporter. Because an exogenous neurotransmitter is introduced, the analyte being detected is known, and selectivity is not a problem. After a dopamine... 

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