Enzyme electrodes theophylline

McNeil, C. J. Cooper, J. M. Spoors, J. A. Amperometric enzyme electrode for determination of theophylline in serum. Biosens. Bioelectron. 1992, 7, 375-380. 

Catalase has also been used as an enzyme label in competitive heterogeneous enzyme immunoassays. Catalase generates oxygen from hydrogen peroxide with the oxygen determined amperometrically with an oxygen electrode. This approach has been demonstrated for a-fetoprotein theophylline and human serum albumin... 

Haga et al. developed another type of immunosensor by combining an enzyme membrane immunoassay and an enzyme sensor using oxygen electrodes (HI). In this assay antigen molecules (theophylline) are attached on the surface of the liposomes and an enzyme (horseradish peroxidase) is encapsulated in the sensitized liposome. When antibody (antitheophylline antibody) and complement are added, the enzyme is released by the liposome lysis. The enzyme activity with the NADH-NAD reaction can be determined by the oxygen electrode. When antigen is added, it competitively binds to antibodies, then liposome lysis and enzyme activity are decreased. The sensitivity of this method for theophylline determination was reported as 0.7 ng/ml. 

Umezawa et al., 1982), or with fluorescence markers (Ishimori et al., 1984). The latter system was shown to be most sensitive, the detection limit being 10-15 mol/L Double signal amplification can be obtained by inclusion of enzymes in the liposomes (Brahman et al., 1984). Thus, Haga et al. (1980) entrapped HRP in sensitized liposomes and used the liposomes to determine theophylline. The rate of HRP liberation was monitored by measuring the NADH oxidase activity of HRP with an oxygen electrode. The electrode response correlated with the theophylline concentration in the sample between 4 and 20 nmol/L... 

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