Measurement of pH and dissolved oxygen within cell culture media using a hydrogel microarray sensor

The sensing of analytes in cell culture media without the introduction of exogenous reagents proves difficult in today's cell culturing systems. In this paper, a completely embeddable microarray sensor that has been developed along with a compact fluorescent imaging system to sense oxygen and pH non-invasively is described. The compact detection system consists of an ultra-bright blue diode source, coupling optics, interference filters and a compact moisture resistant CCD camera. The microarray sensor was created by photoreaction injection molding and contains two separate sensing elements. The system was constructed and the array tested using simple spiked buffer solutions and complex cell media. In addition, the system was coupled to a bioreactor and tested over 2 weeks. The standard error of prediction during a bioprocess for both oxygen and pH detection was 0.75% and 0.092, respectively. The time response of the sensor in the designed flow-through arrangement was less than 90s for both pH and oxygen, well within that needed for cell culture monitoring. Overall, this sensing approach has promise as a lab-on-a-chip type sensor for complete sensing of the culture environment and eventually may be used in a feedback system that allows monitoring and control without human intervention. (C) 2007 Elsevier B.V. All rights reserved.