Gluing jelly back together

There were a lot of great talks in the Liquids 2014 conference, but one stood out. It stood out because it was based on a beautifully simple idea, and because it might just save lives. The talk was by Ludwik Leibler (ESPCI, Paris). It considered the problem of how to stick two polymer gels together. Polymer gels are soft solids that are mostly water but are solid because long polymer molecules form a network inside them. Many foods are polymer gels. Jelly is a classic example.

So, the problem Leibler and his coworkers started with can be stated as follows: If I take some jelly and cut it in two, how do I stick the two halves together? Now, there is interesting physics in rebuilding sliced jelly desserts but it is not exactly a key challenge of the 21st-century. In the run up to next year’s election, Cameron and Miliband are unlikely to be competing to launch multi-million-pound initiatives to rebuild your desserts. However, the tissue which makes up our body is basically a very complex gel, so sticking complex gels together is something all surgeons have to do. And the better they can do it, the more people will survive even very difficult surgery.

Having considered the problem. Let’s look at the key idea. Roughly speaking it starts with the observation that all our glues are polymers. Superglue works by polymerising, the sticky bits of Post-It notes are polymers, etc. So OK, you need a polymer to stick things together. But here we are sticking polymer gels together so we already have polymers. So here the glue does not need to contain polymers — they are already there. all it needs to do is to give the polymers a surface to stick to.

Leibler and coworkers chose the surfaces of nanoparticles, particles about about 10 nanometres across. So Leibler’s glue is kind of an inverse glue. Usually we have surfaces and add a polymer-containing-glue to stick them together. Here, we have polymers and add a surface-containing-glue to stick them together.

So far this is a lovely piece of lateral thinking. And they showed it works in a paper in Nature in January. Then they went on to show that it could actually glue living tissue together. This was in experiments on rats that were published in April. Even with messy wet living tissue, simple solutions of these nanoparticles were as good if not better than the methods surgeons currently use – at least in the cases studied. The nanoparticles stuck together cut tissue in seconds – in the talk Leibler showed movies of the solution being spread on cut tissue and the cut tissue just being pressed together and sticking. Just amazing.

The methods surgeons currently use are sutures, i.e., stitches, and polymer glues (relatives of SuperGlue). These work, but there is scope for improvement. Stitches are not ideal for very delicate tissue like lungs.

There is a long way to go before nanoparticle glues are used in surgery on humans, and problems may arise in their development. But maybe, just maybe, in ten or so years, you or someone you may know won’t have stitches, it will be nanoparticle glue instead.

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