Science Interviews


Tue, 15th Mar 2016

Is freeze-dried blood the future?

Dr Krishnaa Mahbubani, The University of Cambridge

Listen Now    Download as mp3 from the show Cambridge Science Festival: Battle of the Brains

What if you could send soldiers to war with a packet of their own blood in theirBlood Donation Sticker backpack? Ready to use at a moments notice? Dr Krishnaa Mahbubani is working on this becoming a possibility and like a Pot Noodle, you just add water. She brought along a selection of foods to help explain...

Krishnaa -   Today, Iíve brought some freeze dried blood, some actual blood and also some tomatoes and dried pineapples.

Smith - What are you going to make - a pizza?

Krishnaa - Well not exactly.  Iím going to show you how and why I freeze dry blood.  So Iíve got some tomatoes here that are similar to your red blood cells; theyíre round, they have a membrane on the outside of them and theyíre full of liquid inside.

Smith - Theyíre also in a plastic bag!

Krishnaa -   Well thatís more just so theyíre easier to carry around - just like your blood vessels. So, I have some tomatoes there, which I then froze.  As you can see here theyíre kind of solid.  You can have a little feelÖ

Smith - They are pretty hard!

Krishnaa - I then allowed them to thaw out and what I had now having frozen and thawed out my tomatoes; they kind of look quite grim and grose and theyíreÖ

Smith - If I give these a squeeze, theyíre quite squiggy.

Krishnaa -   Yes, theyíre pretty much not going to be there pretty much.  So, this is the problem with trying to freeze thing. If you donít freeze them properly and carefully, when you thaw them out they just turn to mush.

Smith - Why does that happen?

Krishnaa -   Well thatís because when water freezes, it actually expands.  So all the water inside your cells expand and cause the membrane on the outside to explode.

Smith - You make big ice crystals inside the cells which busts them open?

Krishnaa - Absolutely.  So thatís pretty much what happens when you freeze them and when you thaw them, the same thing happens.  As you thaw them, the water expands when it comes up to about 4 degrees, and that causes any residual cells that hadn Ďt quite exploded before to explode again.

Smith - So I can see the problem with blood.  If we just took a blood sample from a person and put that in the freezer, all the blood cells would basically bust open and the blood would become useless.

Krishnaa - Absolutely!  All youíll have is the red material inside your blood, which is the haemoglobin, which really does work by absorbing the oxygen onto it but, without the cell around it, it  wonít go anywhere in your body, so itís kind of useless.

Smith - Why do we need to freeze blood at all?  Why would that be useful?

Krishnaa - Blood at the moment when we take it, we put it in the fridge and it can only be stored for a very short period of time and that means we canít really store it; we canít move it to places where we need it as well.  So when people are at war and we want to transport blood out to them, we canít really do that because itís very tricky to keep the temperature constant so that the blood stays where you want it to be and in best condition.

Smith - And also, itís better to have your own blood isn'tí it, if you can?

Krishnaa - Absolutely!  If you have the opportunity of wandering around with a bag of your own dry blood in your backpack, if anything were to happen to you, youíd just mix the pack together so the liquid mixes with your dried blood and then off you go.  They can, actually medically put the blood back into you and youíre good to go.

Smith - Have you got it working?

Krishnaa - WellÖ not quite there yet.  Chris loves to ask me this question but Iím not a big fan of answering it.  Iím still working on it and itís getting better.

Smith - Okay, so what are you doing to try to make it so that blood can be frozen and what is this in front of us?  Is this examples of it?

Krishnaa - Yes, so hereís some examples of it.  So Iíve got some blood that I tried to freeze dry rather than just freeze alone, which is quite tricky.  What I do is I freeze the in small little vials because, obviously, I donít want to use loads of it initially when Iím doing different tests.  So I freeze small amounts of it and then what I do is I pull the pressure down so I make it very cold and make it very low pressure and what that does, it changes the boiling point of water within the blood.  So, at that pressure Iím able to boil the water out even though the temperature is well below zero.  So, as a result, I can end up with a very dry cake and they use this technique for fruits and vegetables.  I have here some freeze dried pineapple which Chris can have a little taster of.  Itís quite crunchyÖ

Smith - Okay so this is just literally chunks of yellow stuff and they donít look that appetizing but Iíll eat it.

Krishnaa - They donít look very tasty but theyíre actually fine.

Smith - Okay yes, itís pineapple.

Krishnaa - It does taste like pineapple and the idea that Iím using for my freeze dried blood is that you can just add water.  So what we did earlier was add some pineapple into a jar and then we added a bit of water into it and now we just let it re-hydrate again and what you have are swollen up looking like quite regular pineapple....

Smith - It doesnít look great but it does look like pineapple.

Krishnaa -   It does actually look like....

Smith - Does it taste alright?

Krishnaa - Yes. It actually tastes like pineapple.

Smith - Mmm.  But you wouldnít want to inject that into somebody would you? That wouldnít make a good blood transfusion.  So how do you turn the pineapple trick into blood that will work?

Krishnaa - So what have are little cakes of blood and the idea is weíll have two packs next to each other so you can actually just mush the liquid straight into the bloodÖ

Smith - Is that a scientific term - mush?

Krishnaa - Well not really, but the idea is itís going to be in soft packs so you can actually squeeze the two packs together to allow the whole mixture to come together.  What we do is we add it togetherÖ

Smith - Weíve got a little bottle here and itís gotÖ It looks like a big pill actually - a sort of browny red stuff in the bottom - and you just added about half a bottle in this little bottle of waterÖ

Krishnaa - Yes.  So what it is is just a cake of blood because itís effectively just the blood dried up with all the water removed, and now all Iíve done is add a bit of water to it, and Iíve shaken it up and itís gone back into its liquid form.  Now here here it looks much darker than the red blood; thatís because I havenít oxygenated the water to make it go red which is what makes your blood nice and red.  So itís a bit darker just because itís not much oxygen in it.

Smith - And if I put this reconstituted freeze dried, or previously freeze dried blood, under the microscope, do I actually see blood cells in there or do I just see a mess?

Krishnaa - No.  Youíd actually see quite a few blood cells in thereÖ

Smith - Quite a fewÖ or like how many?  What percentage - come on?

Krishnaa - About 8% of blood cells in there compared to the regular - what I started with.

Smith - So thereís a little way to go but the fact is, when I spoke to you a few years ago it was much worse than that so youíve actually made quite substantial progress.

Krishnaa - 8% is a significant improvement already but Iíve got a fair way to go.

Smith - And how have you made that difference?  What have you done to mean that youíre now getting almost one in ten of the cells you freeze actually coming back to life?

Krishnaa - So what weíve done is weíve added different materials into it, known as cryoprotectants or lyoprotectants. We add these things to stop the damage happening during the freezing and during the drying process. Weíre starting to look at different things we can add to the blood that are not toxic and are not bad for us so that when we do transfuse them back into ourselves, we donít have to remove them and that is helping the keep the cells stronger and alive. Itís also maintaining the chemical structure within the cells.

Berrow - Iíve got a very important question and thatís how far are we away from being able to freeze dry a whole person?

Krishnaa - Weíre actually a very, very long way away from that.  And that is very simple. Itís because ice, when it forms, is an excellent insulator so when the ice forms on the outside, the inside of you doesnít freeze up fast enough and so, because you're a very large person (youíre not a tiny little cell), itís going to take a very long time to get you to freeze all the way down the middle and itís going to take a very, very long time to get all of that water out as well.  So, right now, not really possible.


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