Premium
Dual Excitation Ratiometric Fluorescent pH Sensor for Noninvasive Bioprocess Monitoring: Development and Application
Author(s) -
Kermis Haley R.,
Kostov Yordan,
Harms Peter,
Rao Govind
Publication year - 2002
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp0255560
Subject(s) - fluorescence , chemistry , analytical chemistry (journal) , bioprocess , photobleaching , chromatography , chemical engineering , optics , physics , engineering
The development and application of a fluorescent excitation‐ratiometric, noninvasive pH sensor for continuous on‐line fermentation monitoring is presented. The ratiometric approach is robust and insensitive to factors such as source intensity, photobleaching, or orientation of the patch, and since measurements can be made with external instrumentation and without direct contact with the patch, detection is completely noninvasive. The fluorescent dye 8‐hydroxy‐1,3,6‐pyrene trisulfonic acid was immobilized onto Dowex strongly basic anion‐exchange resin, which was subsequently entrapped into a proton‐permeable hydrogel layer. The sensor layer was polymerized directly onto a white microfiltration membrane backing that provided an optical barrier to the fluorescence and scatter of the fermentation medium. The ratio of emission intensity at 515 nm excited at 468 nm to that excited at 408 nm correlated well with the pH of clear buffers, over the pH range of 6–9. The sensor responded rapidly (<9 min) and reversibly to changes in the solution pH with high precision. The sterilizable HPTS sensor was used for on‐line pH monitoring of an E. coli fermentation. The output from the indwelling sensor patch was always in good agreement with the pH recorded off‐line with an ISFET probe, with a maximum discrepancy of 0.05 pH units. The sensor is easily adaptable to closed‐loop feedback control systems.