Caffeine, sensoring

According to Schneider and Chandler (1973), depolarization of the T-tubules affects sensors which open Ca " channels in the SR. The sensors are modified Ca channels which act as voltage sensors (Tanabe et al., 1987). The signal from the sensor reaches the SR and opens the Ca channels with the release of Ca to the myoplasm. The Ca channels in the SR system are opened by micromolar [Ca ], mM [ATP], and caffeine but are inhibited by Mg (Smith et al., 1986 Rosseau et al., 1988). The channels are closed in resting muscle and are opened when the voltage sensor is activated. 

Zougagh, M., Valcarcel, M., and Rios, A., Automatic selective determination of caffeine in coffee and tea samples by using a supported liquid membrane-modified piezoelectric flow sensor with molecularly imprinted polymer. Trends Anal. Chem., 23, 399, 2004. 

Lvova et al. [100] Caffeine, catechines, sugar, amino acid L-arginine Natural coffee, black tea and different sorts of green teas Glucose oxidase/with glutaraldehyde and BSA, then covered with an aromatic polyurethane membrane Carbon paste screen-printed electrodes/ potentiometric (different active components on each of 30 sensors to construct an array) Iron hexacyanoferrate Prussian Blue, Fein[Fen(CN)6]3... 

LAI E P C, FARFARA A, VANDERNOOT V A, KONO M and POLSKY B (1998), Surface plasmon resonance sensors using molecularly imprinted polymers for sorbent assay theophylline, caffeine and xanthan , Can J Chem, 76, 265. 

LIANG c, PENG H, bao x, nie L and yao s (1999), Study of a molecular imprinting polymer coated BAW bio-mimic sensor and its application to the determination of caffeine in human serum and urine , Analyst, 124, 1781-1785. 

As with DNA aptamers, there is a trend towards applying RNA aptamers to a particular application. Allosteric ribozyme sensors have been developed which are specific for caffeine and aspartame. " Using a fluorescence-based assay, caffeine or aspartame may be detected in solution over a 0.5 5mM concentration range. Aptamers designed to malachite green (151) or other triphenylmethane dyes have been developed that enhance the fluorescence of the dye up to 2300-fold. " A further fluorescence-based assay has been... 

Diffusion of materials out of a PSi sensor was monitored by Koh and coworkers in a proof-of-concept device for monitored drug delivery applications [29], Poly-methyl methacrylate (PMMA) containing 0.25 mg/ml caffeine was first cast onto a freestanding PSi thin film. Exposure of this composite material to a pH 7 buffer caused a time-dependent decrease in the intensity of reflection at a fixed wavelength, or alternatively a time-dependent blue shift of the peak, corresponding to diffusion of the small molecule out of the PMMA-PSi composite. These data correlated well with appearance of caffeine in the buffer solution, as measured by UV-Vis spectrophotometry. 

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],... 

Lai, E.P.C. Fafara, A. VanderNoot, V.A. Kono, M. Polsky, B. Surface plasmon resonance sensors using molecularly imprinted pol5mers for sorbent assay of theophylline, caffein, and xanthine. Can. J. Chem. 1998, 76, 265-273. 

Liang, C. Peng, H. Bao, X. Nie, L. Yao, S. Study of Molecular Imprinting Polymer Coated Baw Bio-Mimetic Sensor and Its Application to the Determination of Caffeine in Human Serum and Urine. Analyst 1999, 124, 1781-1785. 

Q. Chen, J. Zhao, Z. Guo, X. Wang, Determination of caffeine content and main catechinscon-tents in green tea (Camellia sinensis L.), using taste sensor technique and multivariatecalibra-tion. J. Food Compos. Anal. 23, 353-358 (2010)... 

Alizadeh, T. Ganjali, MR. Zare, M Norouzi, P. (2010). Development of a voltammetric sensor based on a molecularly imprinted polymer (MIP) for caffeine measurement. Electrochimica Acta, 55,1568-1574. 

Ebarvia et at reported two piezoelectric quartz sensors for caffeine based on MIPs [443,447]. In one work they coated a piezoelectric quartz sensor with MIPs templated by caffeine. They used the copolymerization reaction of methacryhc acid and ethylene glycol dimethacrylate monomers, using azobis(isobutyronitrile) as the initiator in chloroform. The sensor response was reported to be linear in the range of 1 x 10 mg mL and 1x10 mg mL in a stopped flow measurement mode [447]. In another work they used imprinted polymethacrylic acid to the same end, and reported a linear relationship between the frequency shift and the logarithm of the concentration between 1 X 10 up to 1 mg/mL and a detection limit of 5.9 X 10 mg/mL [443]. 

B.S. Ebarvia and E Sevilla, Piezoelectric quartz sensor for caffeine based on molecularly imprinted polymethacrylic acid, Sens. Actuat B-Chem., 107 (2) 782-790, 2005. 

B.S. Ebarvia, C.A. Binag and F. Sevilla, Biomimetic piezoelectric quartz sensor for caffeine based on a molecularly imprinted polymer, Anal. Bioanal. Chem., 378 (5) 1331-1337, 2004. 

Fig. 13.9 Discrimination of standard solutions containing caffeine, paracetamol, or acetylsalicylic acid using a LDA model based on a subset of E-tongue sensors, selected by the SA variable selection algorithm.

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