CASTDan:Abstract13
Kostov, Y., Kermis, H., Harms, P., Rao, G. (2002) Dual Excitation Ratiometric Fluorescent pH Sensor for Noninvasive Bioprocess Monitoring: Development and Application. Biotechnol. Prog. . 18, 1047-1053.
Abstract
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.
