2.7. Pyruvate decarboxylase-containing tissues
He and Rechnitz (1995) exploited the fluorescence detection in plant tissue-based biosensors, to demonstrate its better performance. They coupled corn kernel tissue rich in pyruvate decarboxylase to a fibre-optic CO2 electrode. Pyruvate is decarboxylated to acetaldehyde by this enzyme and the reaction can be followed by monitoring the CO2 release. Although the most commonway to measure CO2 is by the corresponding CO2 membrane electrode, a fibre-optic CO2 optrode can also be used if a pH-sensitive fluorescent dye is coupled to the system.The authors compared these electrodes, observing much shorter response times and slightly lower detection limits with the optical one. The lifetimewas of only 7 days; nevertheless, the lifetimewas the same with the CO2 membrane electrode, demonstrating that the irradiation from the fibre probes did not cause any damage to the tissue.