Enzyme/indicator optrode

Keywords. polyelectrolyte self-assembly, organic dyes, enzyme/indicator optrode, immunoglobuline, UV-visible spectroscopy, SPR, interferometry... 

Enzyme/indicator optrodes for registration of enzyme reactions and their inhibitors, such as heavy metal ions and pesticides, can be produced by PESA technique. Composite films containing the enzyme urease and cyclo-tetra-chromotropylene as indicator molecules show some characteristic spectral transformations caused by urea decomposition. The reaction of inhibition of urease by heavy metal ions can be also registered with this method. Further development of the enzyme sensors and sensor arrays lies in finding suitable pairs of enzyme/indicator, their deposition by PESA method and studying the enzyme reactions (including inhibition) with UV-vis spectroscopy. 

The carrier used for this purpose consisted of a 0.1 M phosphate buffer of pH 7. The appearance of the sensing microzone is shown in Fig. 5.5.B. The oxygen optrode used was based on a 10-pm silicone rubber film containing dissolved decacyclene as indicator (S) that was fixed on a 110-pm thick polyester support (PS). A 9-pm black PTFE membrane (I) was used for optical insulation. The dye fluorescence was found to be markedly dependent on the concentration of oxygen, which exerted a quenching effect on it. The enzyme (glutamate oxidase) was immobilized on a 150-pm thick immunoaffmity membrane (E). The sensor was prepared similarly as reported by Trettnak et al. [7]. 

Several attempts to incorporate other organic indicators, such as methyl red (MR) and thymol blue (TB) sodium salts, into the PESA films has been made in order to form the optrode pairs with other enzymes. The organic indicators mentioned above have only one anionic group per molecule, which makes them difficult to alternate with cationic polymer. MR and TB were mixed with PSS, and then mixed layers of TB/PSS or MR/PSS were alternated with PAA... 

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