Conditioned DMEM – re-try
Last week, I did a couple experiments based on a suggestion by Tom. The pH of DMEM starts out quite high and then buffers down into physiologic range after some time in the incubator. Tom surmised that a short exposure of the chips to high DMEM pH might hasten discoloration. To test this out, I simply allowed DMEM to “condition” in the incubator for 1 hour before adding the membrane chip. DMEM right out of the bottle was control. Last week, I showed that conditioned the DMEM had no beneficial effect, but the chips were covered in bacteria. Here are the results from this week (from w312, no RTP, DMEM+10%FBS):
Again, short-term exposure of chips to a 1-hour spike of high DMEM pH isn’t speeding up the discoloration. Here’s how DMEM pH changes with time:
There is about an hour before DMEM pH reaches and stabilizes within the physiologic range (~7.4). Unfortunately, a short exposure of membrane chips to high pH doesn’t explain discoloration.
In the second figure, is Exp 1 unconditioned and Exp 2 conditioned?
Nope, two different experiments. From this graph, you can assume that conditioned media (after 1 hour in incubator) is about pH 7.4, but unconditioned media (time = 0) is about pH 7.8.