Continuous pH monitoring in a perfused bioreactor system using an optical pH sensor

Abstract

Monitoring and regulating the pH of the solution in a bioprocess is one of the key steps in the success of bioreactor operation. An in-line optical pH sensor, based on the optical absorption properties of phenol red present in the medium, was developed and tested in this work for use in NASA space bioreactors based on a rotating wall-perfused vessel system supporting a baby hamster kidney (BHK-21) cell culture. The sensor was tested over three 30-day and one 124-day cell runs. The pH sensor initially was calibrated and then used during the entire cell culture interval. The pH reported by the sensor was compared to that measured by a fiber optically coupled Shimadzu spectrophotometer and a blood gas analyzer. The maximum standard error of prediction for all the four cell runs for development pH sensor against BGA was +/-0.06 pH unit and for the fiber optically coupled Shimadzu spectrophotometer against the blood gas analyzer was +/-0.05 pH unit. The pH sensor system performed well without need of recalibration for 124 days.

In situ monitoring of 3D in vitro cell aggregation using an optical imaging system

“…In bioreactor applications, other groups have reported the use of optical methods (Ulber et al, 2003;Wolfbeis, 2004) to monitor glucose levels (Hantelmann et al, 2006;Jung et al, 2002), pH (Ge et al, 2006;Jeevarajan et al, 2002), cell viability (Gloeckner et al, 2001), and oxygen (Roy et al, 2001) during in situ culture and we envisage being able to incorporate these technologies into the system described here by adding the necessary sensors. We intend to use the data obtained using such techniques, combined with detailed aggregate measurements, to develop a fully automated bioreactor system for cell aggregation.…”

Haematopoietic Culture Systems

“…Control of pH has been attempted through the use of buffers and by modulating cellular oxidative activity by decreasing the concentration of glucose in the culture medium (Tennant 2000). More importantly, the spatial in-homogeneities inherent to each culture system and within each separate culture have yet to be addressed and make pH monitoring and control essential for consistent and reproducible culture results (Jeevarajan 2002). Hence, the control of pH should be a critical factor in the design and operation of f f bioreactors.…”

pH prediction and control in bioprocesses using mid‐infrared spectroscopy

“…Among the acid-base colored indicators, phenol red has been the most frequently used, due to its low cytotoxicity. Reported applications include the on-line monitoring of tissue cultures (Xu et al, 2006) and the pH control of a perfused bioreactor (Jeevarajan et al, 2002). Concerning fluorescence spectroscopy, several different dyes, such as carboxy-fluorescein (John et al, 2003), 8-hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt (HPTS; Kermis et al, 2002) and cyroxynaphtofluorescein (Song et al, 1997) have been used for pH monitoring in culture media.…”