Use of more than one indicator, each responding to a different parameter or bio-reaction component, is proposed to improve the sensor performance. In order to demonstrate the feasibility of this concept, glucose was chosen as model analyte, and the well known glucose oxidase (GOD) reaction was employed to measure its concentration. An analytical signal was obtained by using two indicators, one sensitive to the oxygen and the other one sensitive to pH changes that result due to the enzymatic activity. Indicators with common absorption wavelengths but different fluorescence emissions were chosen. A further condition for choosing these indicators was their overlapping absorption spectra with GOD. Energy transfer between the various resulting pairs, namely GOD-ruthenium complex, GOD-fluoresceine, fluoresceine-ruthenium was investigated. This preliminary work suggests that the photostability of a biomolecule, and hence that of the sensing element in an optical biosensor, can be augmented by using a suitable indicator combination.
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