Optical imaging in microfluidic bioreactors enables oxygen monitoring for continuous cell culture

Geeta Mehta

Associate Professor

mehtagee@umich.edu

3044 NCRC, Building 28

T: (734) 763-3957

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Dhruv Sud, Geeta Mehta, Khamir Mehta, Jennifer Linderman, Shuichi Takayama, and Mary-Ann Mycek (2006)

JOURNAL OF BIOMEDICAL OPTICS, 11(5).

For the first time, a fluorescence lifetime calibration method for anoxygen-sensitive dye ruthenium tris (2,2'-dipyridyl) dichloridehexahydrate (RTDP) is applied to image oxygen levels in poly (dimethylsiloxane) (PDMS) bioreactors containing living C2C12 mouse myoblasts.PDMS microsystems are broadly used in bioengineering applications due totheir biocompatibility and ease of handling. For these systems, oxygenconcentrations are of significance and are likely to play an importantrole in cell behavior and gene expression. Fluorescence lifetime imagingmicroscopy (FLIM) bases image contrast on fluorophore excited statelifetimes, which reflect local biochemistry. Unique attributes of thewidefield, time-domain FLIM system include tunable excitation (337.1 to960 nm), large temporal dynamic range (>= 600 ps), high spatialresolution (1.4 mu m), calibrated detection (0 to 300 +/- 8 mu M ofoxygen), and rapid data acquisition and processing times (10 s). Oxygenlevels decrease with increasing cell densities and are consistent withmodel outcomes obtained by simulating bioreactor oxygen diffusion andcell proliferation. In single bioreactor loops, FLIM detects spatialheterogeneity in oxygen levels with variations as high as 20\\%. Thefluorescence lifetime-based imaging approach we describe avoidsintensity-based artifacts (including photobleaching and concentrationvariations and provides a technique with high spatial discriminationfor oxygen monitoring in continuous cell culture systems. (c) 2006Society of Photo-Optical Instrumentation Engineers.

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