RNA/Sample storage experiment

Before I launch into extracting the remaining 28 placentas, J~ wants me to run through a quick experiment:

The RNAextraction kit that I'm using (this probably holds for most RNA kits actually) calls for a small amount of tissue (15-50mg). As I am extracting placenta which routinely weigh up to 500mg (0.5g) I have a ton of extra tissue. I have an issue though, as placentas are highly complex: composed of at least 3 different cell types arranged in layers. This means that I cannot just cut off a small bit of placenta and use that (it isn't a random sample of the entire tissue - maybe I would end up with just 1 layer etc...). Instead I have to homogenize the entire sample first (normally with liquid Nitrogen) and then use part of the homogenized tissue. This sucks because if I mess something up, I ruin the entire sample.

Aside from the risk of ruining my samples, it sounds pretty straightforward. But it's not. Once a tissue is homogenized it has a much higher risk of RNA degradation (all the RNAses have been released from their cellular confines) and cannot just be put back in the freezer. Instead I add it to the first buffer of the RNA kit - in this case it's called "RNAsolv." The volume of buffer depends on the weight of the tissue  (in this kit it's 1ml/30mg) so with a 500mg placenta, I will end up with 500mg*1ml/30mg=~17ml of placenta-buffer slurry and I only need 1ml of buffer (30mg of tissue). Therefore I am left with obscene quantities of blueish-brown placenta slurry.

The question is: can we do anything with this slurry? And more specifically: is there any way to keep some of this around so that if I do mess up an RNA extraction, I can go back to the slurry mixture and just re-extract RNA instead of loosing the sample entirely?

To test this I will work through the extraction and at periodic points, freeze some of the sample, then in a couple days, thaw it out and finish the extraction. Here's an outline of the experiment:

This way I have 3 treatments: (1) "never frozen", (2) "top layer frozen" (freeze the liquid layer of the Phenol-Chloroform extraction), and (3) "buffer frozen" (freeze the RNAsolv - phenol - buffer right away). Each Treatment will be duplicated to get a sense of the variance.

I have just finished the extraction from #1 and I will finish up #2 and #3 on Wednesday. Then they can go on the bioanalyzer and we'll see if it works.

And, just because concentration is so important, here are the nano-drop values from these samples:
Never froze 1:       487ng/ul
Never froze 2:       546ng/ul
Top layer froze 1:  564ng/ul
Top layer froze 2:  530ng/ul
Buffer froze 1:      570ng/ul
Buffer froze 2:      549ng/ul