Lecture by Humbert Flamm in the context of the Course: "Tumour Hypoxia: From Biology to Therapy III". For the complete e-Course see http://www.myhaikuclass.com/MaastroClinic/metoxia

1. METOXIA Course
Global and local oxygen control in in vitro systems
Hubert Flamm, IMTEK Freiburg
06.10.2012
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

2. Learning objectives
• Monitoring – The only way to get oxygen under control
• Cell cultures – Physics behind oxygen distribution
• Oxygen production – Smart solution with potential
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

3. Monitoring – Its worth the effort
• Which oxygen tension does the cell see?
• Monitoring as control loop
input
• How and where can we detect pericellular oxygen levels?
− Optical dip-in sensor (Fluorescence)
− SCCF platform (Electrochemical)
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

4. Cell culture oxygenation
+ well defined environment
+ „clean room“ conditions
- long regulation path
- global regulation
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

5. Physics – Culture model
pO2 atmosphere
c0
h medium
ccells cells
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

6. Physics – Partial pressure
What is the partial pressure of oxygen gas above the medium?
n
ptotal = ∑ pi
i =1
ptotal = p N 2 + pCO2 + pO2 + pH 2O
John Dalton, 1766-1844
Assumption: Ideal gas
pO2 = vol % O2 * patm − 60hPa
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

7. Physics – Culture model
pO2 atmosphere
c0
h medium
ccells cells
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

8. Physics – Solubility of oxygen
How many oxygen disolves in the cell medium?
c0 = k H * pO2
c0 = k H (T , S ) * pO2 ( patm , pH 2O )
William Henry, 1774 -1836
c0
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

9. Physics – Culture model
pO2 atmosphere
c0
h medium
ccells cells
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

10. Physics - Oxygen diffusion
What happens if cells metabolise oxygen?
Cells consume oxygen with rate −j
pO2 atmosphere
c0
h medium
-j
ccells cells
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

11. Physics - Oxygen diffusion
What happens if cells metabolise oxygen?
Diffusion flux can be described by Fick´s first law
ccells − c0 jh
j = −D ccells = c0 +
∆h D Adolf Fick, 1829-1901
pO2 atmosphere
c0
h medium
-j
ccells cells
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

12. Oxygen control - Strategies
jh
ccells = k H (T , S ) * pO2 ( patm , p H 2O ) +
D
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

13. Oxygen control – Incubator box
• Feedback loop CELLS / INCUBATOR
– Oxygen sensor for pericellular measurement
– Software interface Sensor / Incubator
• Limitations
– Same global atmosphere for all cell cultures
– Long control loop (long response time)
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

14. Oxygen control – Single flask supply
Inside incubator:
– Individual gas supply in each (critical) flask for fine-tuning
– Easy to implement, but additional equipment needed
– Shorter regulation loop (shorter response time)
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

15. Oxygen control – Medium height
Medium height is influencing oxygen concentration at cells
jh
ccells = c0 +
D
Height could be altered:
– static (if something is known about oxygen consumption)
– dynamic with feedback to sensor reading
• Problems with forced convection
Increasing viscosity or seldom adjustments
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

16. Oxygen control – Local regulation
External source counter-acting the cellular oxygen consumption
pO2 atmosphere
c0
h medium
ccells cells
j prod > 0
Steady-state: ccells = c0 +
(j cells + j prod ) ∗ h
D
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

17. Oxygen control – Multichamber flask
• Multichamber construction
• Oxygen supply across thin
diaphragm
+ short diffusion path
+ rapid concentration change
- premixed gas required
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

18. Oxygen control – Active O2 production
• Electrolysis of aqueous solutions
• Dosing by diffusion into cell culture chamber
• Voltage / Current, Time [O2]
Cell chamber
Membrane
Electrolyte O2
Platinum electrodes
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

19. Oxygen control – Active O2 production
Cells • high aspect ratio
PDMS
• integration of micro-fluidics
Isolation
Glass Pt
• complex geometries
• plasma enhanced bonding
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

20. Oxygen control – Active O2 production
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

21. Oxygen control – Active O2 production
Video
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

22. Oxygen control – Active O2 production
300
290
2
250nA (0.476 mA/cm )
280 2
200nA (0.381 mA/cm )
oxygen / µM
2
100nA (0.190 mA/cm )
2
270 50nA (0.095 mA/cm )
2
20nA (0.038 mA/cm )
260
250
0 2 4 6 8 10
time / min
350
340
330
• Linear production
oxygen / µM
Y=A+B*X
320 Parameter Value Failure
------------------------------------------------------------
A 248,00183 2,15675
310 B 215,74322 6,16445
------------------------------------------------------------
• Wide operation range
R SD N P
300
-----------------------------------------------------------
0,99918 1,31363 4 8,15423E-4
------------------------------------------------------------
290
280
0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50
2
current density / mA/cm
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

23. Oxygen control – Active O2 production
cell chamber refill
370
350 • Fast response time
330
• Predefined profiles programmable
oxygen / µM
310
290
270
250
8 23 38 53 68 83 98 113 128
time / min
285
275
oxygen / µM
• Longtime stability 265
• Short pulses and long ramps 255
0 20 40 60 80 100 120
time / min
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

24. Oxygen control – Active O2 production
Simulation as design tool Measurement as simulation input
300
290
2
250nA (0.476 mA/cm )
280 2
200nA (0.381 mA/cm )
oxygen / µM
2
100nA (0.190 mA/cm )
2
270 50nA (0.095 mA/cm )
2
20nA (0.038 mA/cm )
260
250
0 2 4 6 8 10
time / min
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

25. Oxygen control – Active O2 production
Where to measure oxygen?
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

26. Oxygen control – Active O2 production
Simulation as guidance for design
• Lateral oxygen profiles possible
• Mimicking of reperfusion
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.

27. Coffee break
• Coffee increases open-mindedness
– Coffee drinkers agree rather than others
• Coffein raises sexual longing – proven for female rats
• Coffee improves short-term memory
• Coffee consumption increases health damages caused by smoking
This course is funded with the support of the METOXIA project
06.10.12 under the FP7 Programme.