Electrochemical Gas Generation for Cell Culture

A scalable array technology for parametric control of high-throughput cell cultivations is demonstrated. Central to this cell culture array is a silicon microfabricated electrolytic oxygen generator. The generator consists of Ti/Pt electrodes patterned at the narrow end of conical hydrophilic silicone microchannels filled with electrolyte. Surface tension forces arising from the conical microchannel geometry push generated gas bubbles away from the electrodes and down the microchannel where the bubbles exhaust into the cell culture. This bubble motion draws fresh electrolyte from an adjacent reservoir onto the electrodes. The oxygen dosage can be precisely controlled in each generator by pulse width modulation of the electrode potential. Devices capable of continuously providing for a wide range of oxygen demands (0-10 umol O2/hr) and operating for days are demonstrated. Lifetime-limiting corrosion of hydrogen-absorbing noble metal electrodes during low-frequency electrolysis can be avoided by using relays to control the electrode potential. Pre-cure silicone additives are also presented as an alternative to plasma surface modification to obtain hydrophilic silicone surfaces.  
A variant of this technology makes use of commercial printed circuit board (PCB) to fabricate the electrochemical gas generation system. Results are presented for an array of eight 250 ul microbioreactors. Each bioreactor contains an independently addressable suite that provides closed-loop temperature control, generates feed gas electrochemically, and continuously monitors optical density. The PCB technology allows for the assembly of additional off-the-shelf components into the microbioreactor array; the use of a commercial ISFET chip to continuously monitor culture pH is demonstrated. The electrochemical dosing system provides a powerful paradigm for reproducible gas delivery to high-density arrays of microreactors. Growth data are presented for Escherichia coli cultured in the array with varying microaerobic conditions using electrochemically generated oxygen. Additionally, data on carbon dioxide generation and pH control are presented.
Publication date: 
July 31, 2007
Publication type: 
Ph.D. Dissertation
Maharbiz, M. M. (2003). Electrochemical Gas Generation for Cell Culture. United States: University of California, Berkeley.

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