Silica shells gives donated blood cells a longer shelf life

Blood transfusions save millions of lives. But, until stem cell biologists can find ways to grow replacement blood in a test tube, we’re solely reliant on people generously giving blood. This can only survive on the shelf in storage for a limited time though, and supplies of some rarer blood groups, including precious O negative blood that can be given to anybody, periodically run short. Now a new breakthrough might have found a way to give donated blood a much longer shelf life, and potentially mask existing blood group markers so that the blood could be given to any recipient. The technique works through a process of “silicification” - a word I initially struggled to say - that involves impregnating the cells with silica particles that form a shell around and through them, and make them more robust.  The University of Cambridge’s Krishnaa Mahbubani works on similar techniques and I asked her to examine the new research, just published in the journal PNAS…

Krishnaa - This paper looks to explore how we can use a technique known as silicification. It's basically replacing the outside structure of a cell with silica to try and stabilise and make red blood cells more manageable through different machines and any other longer term effects that they have to go through.

Chris - Is it sort of like sugar coating? When we sugarcoat fruit and you get an outer shell, is it sort of putting a shell around a cell, then?

Krishnaa - Essentially, that's kind of what it's trying to do. What they do is they dissolve the calcium carbonate, which is basically part of what makes your cells not too squishy. they dissolve that and replace it with silica and in this case it's nano silica material. They're small tiny particles to give it effectively a sugar coated shell.

Chris - Around the outside?

Krishnaa - Not just the outside, but through the entire structure.

Chris - And why do we need to do that?

Krishnaa - Their motivation for this specific paper was looking at using it in systems where we keep, or try and keep, organs outside of the body alive so we can test them, check them, make sure that they're functional. But equally, the idea was also so that they would have red blood cells that are able to be kept significantly longer than they currently do, or even withstand some of the more stressful situations like freezing, which cells tend not to like particularly.

Chris - What about blood groups? Does that come into the equation as well?

Krishnaa - In this paper what they've looked at is the fact that the silica that they put around seems to mask some of these blood group markers. It should effectively turn them all into what is known as a universal cell, so it doesn't matter what blood group you are.

Chris - Because there's been a big crisis recently of not having enough blood and they were short of of O negative blood. That's the universal donor group, isn't it, you can give that to anybody. This masks what's normally around the outside of the cell, so in theory you could give group A blood to a group O person.

Krishnaa - That's the idea, that's what they think this kind of silicification actually can do, but I'm not sure that they've actually fully shown that.

Chris - Tell us first of all how they actually do it.

Krishnaa - What they've actually done is something very similar to what we do if we were trying to get all of our dry fruits ready for Christma. I don't know about you guys, but my grandmother would quite often take lots of dried fruit and then put whiskey and a bit of sherry in, and she'd come in and add some more every couple of weeks. That's essentially what they do is they take the cells and they slowly add different materials into it over a period of time. In this case it's about three to six hours. They're changing the acid levels, so the pH levels change of the solution, and what that does is slowly dissolve out the calcium carbonate and allow these silicon nanoparticles to essentially replace them in the cells.

Chris - Can they see that happening? Have they imaged their cells in order to show that they've now got this coating, this silicification?

Krishnaa - They did do lots of different imaging technologies on it. They tried to use scanning electron microscopy and transmission electron microscopy to essentially show that the structure hasn't changed, but they can't actively show that the silicon nanoparticles have actively replaced the calcium. What they can show is that these silicon nanoparticles will allow certain fluorescent materials to stick to it and not the calcium particles. They have shown that the silica has gone into the cells, but you and I wouldn't be able to physically see the particles going in as the process is happening.

Chris - And, critically, do the cells still work in the aftermath?

Krishnaa - That's the bulk of this paper, is they've gone through a series of different tests in order to show whether or not they still function like they should. They've compared them to a control set of cells - basically your starting red blood cell material that's not been stored, that's not been manipulated - and they tried to show that they do work similarly, not perfectly, but similarly.

Chris - And their lifetime? Because one of the other things that with a red blood cell is it has a certain time it will survive in the body before it dies. Are these cells going to die more quickly because they've had this done to them?

Krishnaa - Unfortunately, they haven't shown the full lifespan within a circulating system. They have tried to put them in animals for about four to six hours and they've shown that the animals don't actively destroy them, which is what our bodies would do if we put foreign cells into it. So, in theory, they have the ability to circulate, but they haven't actually shown a long term circulation. What they have shown is that these cells have potentially got a longer shelf life. Our blood cells that we collect are stored for up to about six weeks. They're hoping that these cells would potentially be able to be kept significantly longer than that because they don't get damaged over time.