Catechol sensor

NOVEL OPTICAL pH SENSORS BASED ON CATECHOL AZO DYE DERIVATIVES... 

Furthermore, the use of Ralstonia eutropha JMP134-containing sensors for the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been described [118,121]. This sensor was sensitive to 2,4-D and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) with a detection Emit of 40 mg 1 with a response time of 15 s. Moreover, catechol, benzoic acid, and sahcylaldehyde caused higher signals, but no or very little signal was obtained for phenol, biphenyl, and the usual substrates such as glucose, fructose, ethanol, and acetate. 

Sensors have also been constructed from some oxidases directly contacted to electrodes to give bioelectrocatalytic systems. These enzymes utilize molecular oxygen as the electron acceptor for the oxidation of their substrates. Enzymes such as catechol oxidase, amino acid oxidase, glucose oxidase, lactate oxidase, pyruvate oxidase, alcohol oxidase, xanthine oxidase and cholesterol oxidase catalyze the oxidation of their respective substrates with the concomitant reduction of O2 to H2O2 ... 

In the simplest way reported in numerous papers for biorecognition, such cells or tissues are selected where the occurence of particular enzyme is known. Plant tissues can be grinded and placed at the transducer surface using dialytic membrane, e.g. spinach leaves for amperometric biosensor for catechol.117 Numerous sensors with potentiometric detection have been reported with slices of animal tissues attached to the transducer surface in the similar way. Cells can be also entrapped in... 

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,... 

Specific catechol determination is demanded in the photographic, paint, and pharmaceutical industries. Neujahr (1980) combined immobilized catechol-1,2-oxygenase with an oxygen electrode and employed the sensor for catechol measurement. The sensor was selective for catechol and 3- and 4-methylcatechol. Phenol, resorcinol, cresol, vanil-line, and dihydroxyphenylalanine (DOPA) did not interfere. 

Write et al. explored direct detection of various phenohc compoimds (phenol, hydroquinone, resorcinol, phloroglucinol, and catechol) using an SPR sensor with intensity modulation and synthetic receptors loaded in a polymer or sol-gel layer [39]. Their preUminary experiments, consisting of the detection of phenols in buffer, suggested that detection of phenols at mUlimolar concentration levels ( 100 iJigmL ) is feasible using this approach. 

At the same time, thin-layer series electrodes were being developed for microbore LCEC (Goto et ai, 1981, 1982). With flow rates of 10-100 //1/min, the arrangement could provide 100% conversion efficiency at each sensor. An automated-trace-enrichment, tandem column system was devised for the direct injection of urine samples containing catecholamines (Fig. 33 A). Samples were injected onto an activated aluminum oxide microbore column with a pH 8.8 Tris buffer. The alumina column was then coupled with the reversed-phase microbore analytical column the catechols were eluted using pH 1.8 mobile phase. The downstream electrode was monitored (Fig. 33B). 

Figure 7 Response of glucose sensor with catechol polymer film. Open circles ImM acetaminophen Filled...

Inorganic ions, drugs, nucleic acids, proteins, and even cells are successful examples of imprinting. In this way, affinity sensors, receptor sensors, and catalytic sensors based on MIPs have been explored. For affinity sensors, immunosensor-like devices were prepared by a 2D MIP technique with molecular imprinting on chemisorbed alkanethiol SAMs then after necessary procedures, vitamins Ki, K2, E, cholesterol, and adamantine could be detected by the strong electrochemical signals yielded. The sensors for nucleic acids, cholesterol, and catechol derivatives can be fabricated first by their adsorption as a template on the ITO surface and then by the treatment of the electrode with adsorbed template using trimethyl chlorosilane from the gas phase. 

Phenolic compounds are found in most fruits and vegetables. These endogenous compounds show interesting properties such as antioxidant activity, enzymatic inhibition and free radical scavenging action [42]. In particular, catechol is a diphenol compound of interest in the food industry and has been involved in ghal cell toxicity. Thus, there is a great appeal to produce novel sensors of higher stability and lower cost for catechol detection [43]. 

Alessio, P., Pavinatto, F.J., Oliveira Junior, O.N., Saez, J.A.S., Constantino, C.J.L., Rodr(guez-M6ndez, M.L. Detection of catechol using mixed Langmuir-Blodgett films of a phospholipid and phthalocyanines as voltammetric sensors. Analyst 135, 2591-1599 (2010). doi 10.1039/c0an00159g... 

The main difference between the two types of sensors is that the first type (based on phenol oxidases or peroxidase) uses a low applied potential (-100 - 0 mV vs. Ag/AgCl) (3), whereas the second type (based on CDH or GDH) needs a higher potential (300 - 400 mV V5. Ag/AgCl) (9,11,13) to be able to oxidize the phenols and therefore the risk of electrooxidizing interfering compounds in the sample is higher. Tyrosinase, laccase and peroxidase can all be used for both phenolic and diphenolic compounds, however, for laccase and tyrosinase the sensitivity is much higher for catecholic compounds (3). CDH and GDH require a quinone, therefore a diphenol or aminophenol is needed. 

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