Quantitative measurement and control of oxygen levels in microfluidic poly(dimethylsiloxane) bioreactors during cell culture.
Microfluidic bioreactors fabricated from highly gas-permeable poly(dimethylsiloxane) (PDMS) materials have been observed, somewhat unexpectedly, to give rise to heterogeneous long term responses along the length of a perfused mammalian cell culture channel, reminiscent of physiologic tissue zonation that arises at least in part due to oxygen gradients. To develop a more quantitative understanding and enable better control of the physical-chemical mechanisms underlying cell biological events in such PDMS reactors, dissolved oxygen concentrations in the channel system were quantified in real time using fluorescence intensity and lifetime imaging of an oxygen sensitive dye, ruthenium tris(2,2'-dipyridyl) dichloride hexahydrate (RTDP). The data indicate that despite oxygen diffusion through PDMS, uptake of oxygen by cells inside the perfused PDMS microchannels induces an axial oxygen concentration gradient, with lower levels recorded in downstream regions. The oxygen concentration gradient generated by a balance of cellular uptake, convective transport by media flow, and permeation through PDMS in our devices ranged from 0.0003 (mg/l)/mm to 0.7 (mg/l)/mm. The existence of such steep gradients induced by cellular uptake can have important biological consequences. Results are consistent with our mathematical model and give insight into the conditions under which flux of oxygen through PDMS into the microchannels will or will not contribute significantly to oxygen delivery to cells and also provide a design tool to manipulate and control oxygen for cell culture and device engineering. The combination of computerized microfluidics, in situ oxygen sensing, and mathematical models opens new windows for microphysiologic studies utilizing oxygen gradients and low oxygen tensions.
Mehta
Geeta
G
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48108, USA.
Mehta
Khamir
K
Sud
Dhruv
D
Song
Jonathan W
JW
Bersano-Begey
Tommaso
T
Futai
Nobuyuki
N
Heo
Yun Seok
YS
Mycek
Mary-Ann
MA
Linderman
Jennifer J
JJ
Takayama
Shuichi
S
D000818:Animals; D019149:Bioreactors; D018929:Cell Culture Techniques / Q000295:instrumentation* / Q000379:methods; D002460:Cell Line; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation* / Q000379:methods; D051379:Mice; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D032446:Myoblasts / Q000502:physiology*; D009757:Nylons / Q000737:chemistry; D010100:Oxygen / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology
D004129:Dimethylpolysiloxanes; D009757:Nylons; C085707:poly(dimethylsiloxane)-polyamide copolymer; D010100:Oxygen