An optical fiber biosensor for the selective determination of hydrogen peroxide has been developed as the base sensor for the construction of multienzyme optodes involving lactate converting enzymes for the analysis of lactic acid. The optode uses the H₂O₂ dependent oxidation of homovanillic acid by horseradish peroxidase (HRP) as the sensing reaction. The fluorescence of the dimeric product formed is used as the measuring signal related to the concentration of H₂O₂. HRP was immobilized on a membrane and combined with a bifurcated fiber optic probe. Under optimized conditions the sensor responds linearly to hydrogen peroxide between 1 micrometers ol/l and 0.12 mmol/l and exhibits a half life of 90 days. Using a lactate oxidase-HRP membrane, the sensor is suitable for lactate measurement with a linear range of 3 micrometers ol/l-0.2 mmol/l. To increase the sensitivity for lactate, lactate dehydrogenase was coimmobilized on the sensor membrane. In the presence of NADH the signal for lactate is amplified fourfold through the internal analyte recycling accomplished by the lactate-converting enzymes.

Date Published: 10 February 1995
PDF: 8 pages
Proc. SPIE 2331, Medical Sensors II and Fiber Optic Sensors, (10 February 1995); doi: 10.1117/12.201240

Published in SPIE Proceedings Vol. 2331:
Medical Sensors II and Fiber Optic Sensors
Anna Maria Verga Scheggi; Francesco Baldini; Pierre R. Coulet; Otto S. Wolfbeis, Editor(s)