Choline, detection

Lapp H., Spohn U., Janasek D., An enzymatic chemiluminescence optrode for choline detection under flow injection conditions, Anal. Lett. 1996 29 1-17. 

Chen HC, Tsai RY, Chen YH, Lee RS, Hua MY. A colloidal suspension of nanostru-ctured poly(n-butyl benzimidazole)-graphene sheets with high oxidase yield for analytical glucose and choline detections. Anal Chim Acta 2013 792 101-9. 

Butyryl-choline detection in such a system can be realized by two different coupling approaches (i) co-immobilization of butyrylcholinesterase on a choline bienzyme electrode, which results in a tri-enzyme electrochemical sensing system (ii) use of solubilized butyrylcholinesterase in a coupled system with an electrode for choline determination, by addition of standard amounts of the dissolved enzyme to the measuring cell. In both cases butyrylcholinesterase activity affects the choline electrode response providing the presence of choline in the solution. Both coupling approaches are suitable for analysis of butyrylcholinesterase inhibitors such as organophosphorus compounds. 

Detection by LDMS and structural elucidation of other secondary metabolite products, generated in the host during the onset of the parasite disease, is discussed. These molecules may serve as additional biomarkers for rapid malaria diagnosis by LDMS. For instance, choline phosphate (CP) is identified as the source of several low-mass ions observed in parasite-infected blood samples in addition to heme biomarker ions. The CP levels track the sample parasitemia levels. This biomarker can provide additional specificity and sensitivity when compared to malaria detection based on heme ion signals alone. Furthermore the observed elevated CP levels are discussed in the context of Plasmodium metabolism during its intra-erythrocytic life cycle. These data can... 

Choline Phosphate—Another Unique LDMS Biomarker for Malaria Detection... 

Figure 8.7 Low mass (choline phosphate) region of a LD mass spectrum of blood from a P. vivax infected human patient (estimated parasitemia approximately 32,000 parasites/pl). Protocol C is used for sample preparation. A commercial LD TOF system is used laser wavelength 337nm. All one hundred single laser shot spectra, obtained from linear scanning of an individual well, are averaged (no data smoothing). The characteristic ions of detected choline phosphate are denoted.

A flow injection optical fibre biosensor for choline was also developed55. Choline oxidase (ChOX) was immobilized by physical entrapment in a photo-cross-linkable poly(vinyl alcohol) polymer (PVA-SbQ) after adsorption on weak anion-exchanger beads (DEAE-Sepharose). In this way, the sensing layer was directly created at the surface of the working glassy carbon electrode. The optimization of the reaction conditions and of the physicochemical parameters influencing the FIA biosensor response allows the measurement of choline concentration with a detection limit of 10 pmol. The DEAE-based system also exhibited a good operational stability since 160 repeated measurements of 3 nmol of choline could be performed with a variation coefficient of 4.5%. 

With the specific suitable oxidases, lactate, choline and glucose could be assayed. Concentration measurements of these metabolites could be performed over at least two decades wit a detection limit of 10 pM for lactate and choline and 20 pM for glucose. 

Marquette C.A., Degiuli A., Blum L.J., Electrochemiluminescent biosensors array for the concomitant detection of choline, glucose, glutamate, lactate, lysine and urate, Biosens. Bioelectron. 2003 19 433-439. 

Acetylcholine + H20 AChE> Choline + Acetic acid Choline + Oz + HzO COx >- Betaine + H202 FIGURE 2.3 Bienzymatic reaction for pesticide detection. 

C. Cremisini, A.D. Sario, J. Mela, R. Pilloton, and G. Paleshci, Evaluation of the use of free and immobilised acetylcholinesterase for paraoxon detection with an amperometric choline oxidase based biosensor. Anal. Chim. Acta 311, 273—280 (1995). 

Fortier [6] found that AQ polymer from Eastman was not deleterious for the activity of a variety of enzymes such as L-amino acid oxidase, choline oxidase, galactose oxidase, and GOD. Following mixing of the enzyme with the AQ polymer, the mixture was cast and dried onto the surface of a platinum electrode. The film was then coated with a thin layer of Nafion to avoid dissolution of the AQ polymer film in the aqueous solution when the electrode was used as a biosensor. These easy-to-make amperometric biosensors, which were based on the amperometric detection of H202, showed high catalytic activity. 

The environment of a cell membrane is often modeled by a monolayer of phospholipid on the air-water interface. Our attempts to detect enantiomeric recognition in such films has largely involved dipalmitoylphosphatidyl choline (DPPC), which has a chiral headgroup situated at the junction of two 16-carbon unit chains. 

The same group reported in 1986 a sensitive and selective HPLC method employing CL detection utilizing immobilized enzymes for simultaneous determination of acetylcholine and choline [187], Both compounds were separated on a reversed-phase column, passed through an immobilized enzyme column (acetylcholine esterase and choline oxidase), and converted to hydrogen peroxide, which was subsequently detected by the PO-CL reaction. In this period, other advances in this area were carried out such as the combination of solid-state PO CL detection and postcolumn chemical reaction systems in LC [188] or the development of a new low-dispersion system for narrow-bore LC [189],... 

On the other hand, several oxidases are known to generate hydrogen peroxide, acting as an oxidant in the CL system, from corresponding substrates. IMERs in which the oxidases are immobilized on adequate supporting materials such as glass beads have been developed. IMERs are often used for flow injection with CL detection of uric acid and glucose, and are also applicable to the CL determination of acetylcholine, choline, polyamines, enzyme substrates, etc., after online HPLC separation. 

In this system, choline formed by acetylcholinesterase is oxidized by choline oxidase and the hydrogen peroxide produced is determined using the luminol/peroxidase CL reaction. The sensor has been used for the analysis of Paraoxon and Aldicarb pesticides, with detection limits of 0.75 pg/L and 4 pg/ L, respectively. Recoveries in the range of 81-108% in contaminated samples of soils and vegetables were obtained. 

A more successful strategy for developing sensitive and facile assays to monitor PLCBc activity involves converting the phosphorylated headgroup into a colorimetric agent via a series of enzyme coupled reactions. For example, phosphatidylcholine hydrolysis can be easily monitored in a rapid and sensitive manner by enzymatically converting the phosphorylcholine product into a red dye through the sequential action of alkaline phosphatase, choline oxidase, and peroxidase [33]. This assay, in which 10 nmol of phosphorylcholine can be readily detected, may be executed in a 96-well format and has been utilized in deuterium isotope and solvent viscosity studies [34] and to evaluate inhibitors of PLCBc [33] and site-directed mutants of PLCBc [35,36]. 

Because the preceding chromogenic assay rely on choline quantitation, the hydrolysis of substrates with headgroups other than choline cannot be followed. To circumvent this problem, another useful protocol was devised whereby the phosphorylated headgroup produced by the PLCBc hydrolysis is treated with APase, and the inorganic phosphate (Pi) that is thus generated is quantitated by the formation of a blue complex with ammonium molybdate/ascorbic acid 5 nmol of phosphate may be easily detected. This assay, which may also be performed in a 96-well format, has been utilized to determine the kinetic parameters for the hydrolysis of a number of substrates by PLCBc [37,38]. 

There is increasing interest in the use of specific sensor or biosensor detection systems with the FIA technique (Galensa, 1998). Tsafack et al. (2000) described an electrochemiluminescence-based fibre optic biosensor for choline with flow-injection analysis and Su et al. (1998) reported a flow-injection determination of sulphite in wines and fruit juices using a bulk acoustic wave impedance sensor coupled to a membrane separation technique. Prodromidis et al. (1997) also coupled a biosensor with an FIA system for analysis of citric acid in juices, fruits and sports beverages and Okawa et al. (1998) reported a procedure for the simultaneous determination of ascorbic acid and glucose in soft drinks with an electrochemical filter/biosensor FIA system. 

Wang, X.-F., et ah, Signat-on electrochemiluminescence biosensors based on CdS-carbon nanotube nanocomposite for the sensitive detection of choline and acetylcholine. Advanced Functional Materials, 2009.19(9) p. 1444-1450. 

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