Fiber-optic Sensor for Continuous Monitoring of Fermentation pH

Agayn, Venetka; Walt, David R.

doi:10.1038/nbt0693-726

Cited by 34 publications

(14 citation statements)

References 20 publications

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“…Given a fluorescent indicator that exhibits a shift in excitation or emission wavelength with pH, the ratio of the emission intensity at the two wavelengths can be used as a robust measure of the pH that is insensitive to orientation, probe concentration, and background fluorescence. Fiber‐optic sensors based on fluorescein (7), seminaphthofluorescein (8), and carboxynaphthofluorescein (9) have been described that rapidly and reliably correlate intensity ratios to pH. The extensive photobleaching that is observed for these dyes is accounted for by the ratiometric approach but would still limit the useful lifetime of the sensor.…”

Section: Introductionmentioning

confidence: 99%

Dual Excitation Ratiometric Fluorescent pH Sensor for Noninvasive Bioprocess Monitoring: Development and Application

Kermis

Kostov

Harms

et al. 2002

Biotechnology Progress

158

103

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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.

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Section: Introductionmentioning

confidence: 99%

Dual Excitation Ratiometric Fluorescent pH Sensor for Noninvasive Bioprocess Monitoring: Development and Application

Kermis

Kostov

Harms

et al. 2002

Biotechnology Progress

158

103

View full text Add to dashboard Cite

show abstract

“…As an alternative, optical sensors (3)(4)(5) have been widely studied and developed; these sensors are inexpensive, miniature, robust, easy to fabricate, suitable for simultaneous analysis of multianalytes, and autoclavable in most cases. Among examples of autoclavable optical sensors are fluorescence sensors for sensing dissolved O 2 in bioreactors (6,7), a fiber-optic pH sensor for fermentation monitoring (8), and a fiber-optic CO 2 sensor for beer fermentation monitoring (9).…”

Section: Introductionmentioning

confidence: 99%

Steam‐Sterilizable, Fluorescence Lifetime‐Based Sensing Film for Dissolved Carbon Dioxide

Chang

Randers‐Eichhorn

Lakowicz

et al. 1998

Biotechnology Progress

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An autoclavable sensing film was developed for monitoring dissolved CO2. The sensing film, based on fluorescence resonance energy transfer (FRET), consisted of a fluorescent donor, an acceptor, and a quaternary ammonium hydroxide, which were doped in a two-component silicone film. As no aqueous solution was used in the sensing film matrix, the sensing film was unaffected by osmotic pressure. Fluorescence lifetime was selected as the sensing parameter, and measured in frequency domain using phase fluorometry. Upon exposure to 20% CO2-saturated water, a 43 degrees increase in phase angle was observed at 100 MHz. The process was fully reversible when the sensing film was exposed to nitrogen-saturated water. The estimated response and recovery times for 90% signal change were 1 min (for a step change from 0 to 6.7% CO2-saturated water) and 1.5 min (for a step change from 6.7 to 3.3% CO2-saturated water). When used for on-line monitoring of dissolved CO2 produced by a culture of Escherichia coli, the sensing film showed a similar trend to that obtained from off-line measurements using a wet chemistry analyzer.

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“…Although the accuracy of pH measurement with an intravascular ISFET sensor is less than usually claimed for off-line analysis on blood samples, it is within the normal physiological variation due to respiration. The measurement of pH can also be achieved using optical methods [119,120]. In this case A2.1.4 Sensor Overview 137 the light is reflected from a surface treated with, usually, an enzyme that reacts optically to the acidity.…”

Section: Ph Sensorsmentioning

confidence: 99%

Sensors for Catheter Applications

2003

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Minimally invasive techniques enable diagnostics and surgery to be performed through a small incision. This greatly reduces the damage to healthy tissue leading to faster recovery times for the patient. However, the surgeon is deprived of the sensory feedback available with normal surgical techniques. Miniaturised sensors can provide this information about location, diagnostics and the treatment. This application severely limits the size of the device, with some catheters being less than 1 mm in diameter. Catheters are usually defined in multiples of 1/3 mm or 1 french. Further important issues are bio-compatibility, safety and the ability of the sensor to withstand the working environment. Sensors able to meet these demands are improving the efficiency of operations and are opening new opportunities for minimally invasive techniques.

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Fiber-optic Sensor for Continuous Monitoring of Fermentation pH

Cited by 34 publications

References 20 publications

Dual Excitation Ratiometric Fluorescent pH Sensor for Noninvasive Bioprocess Monitoring: Development and Application

Dual Excitation Ratiometric Fluorescent pH Sensor for Noninvasive Bioprocess Monitoring: Development and Application

Steam‐Sterilizable, Fluorescence Lifetime‐Based Sensing Film for Dissolved Carbon Dioxide

Sensors for Catheter Applications

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