A mussel-inspired glue for more sustainable sticking

Shamini Bundell

Welcome back to the Nature Podcast, this week: a new more sustainable type of glue...

Nick Petrić Howe

....and what the data say about malnutrition in children. I'm Nick Petrić Howe.

Shamini Bundell

And I'm Shamini Bundell.

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Shamini Bundell

You may not have thought much about it, but glues are everywhere. Most of the modern world from phones and furniture to cars and even buildings is held together by adhesives and society would literally fall apart without them. But while they are ubiquitous glues, like many materials, come with an environmental cost. The majority are made from fossil fuels. And what's more the bonds they create are permanent meaning once glued together, separating components isn't simple, which can hinder processes like recycling. But this week in Nature, a team of researchers are presenting a new type of adhesive which could get around these problems. It's simultaneously strong, reversible, and because it's based on soya oil, much less carbon intensive to produce. The new product mimics a common type of glue called epoxy, which works by combining two chemical groups that react when they come together, forming a bond. But this new adhesive has a twist, it's inspired by sea creatures. For more on the new glue, let's hand over to reporter Anand Jagatia who got the lowdown from researcher Jon Wilker, from Purdue University. Jon started by describing how conventional epoxy glues work.

Jon Wilker

So there's two components in there, one actually has epoxy groups in it. And the other is a different type of compound that will react with the epoxy group. And so that basically locks the material down, sort of locks in all the substrates that you're trying to bind.

Anand Jagatia

So currently, they're sort of building blocks of these epoxies are petroleum based. So what did you try and do to create a more sustainable version of this?

Jon Wilker

In adhesives scale turns out to be really important, right? So if you just think about plywood, I think the number is something on the order of 25 million tons of adhesive are consumed each year just for making plywood. So all of the components that we're going to put into the system have to already be available at massive, massive amounts, soy oil turns out to be one of the most widely produced sustainable organic materials. And what you can do is you can epoxidize it. So the idea would be oh, well, if we can take the petroleum based epoxy compound, and we can substitute in epoxidized soy oil, that'd be great. But it turns out, it's not that simple, because it's not reactive enough to actually cure to a solid and bond anything together. So we added a third component to the system. So for years, we've actually been studying how sea creatures like mussels and oysters actually make adhesives in the ocean. Like if you go to the beach, you'll see all sorts of sea creatures stuck to the rocks, right. And a lot of them are making adhesives to do that. And so we've got tanks of the animals growing in the lab, and we study this. And the animals stick by making proteins that take a mixture of proteins, and they put them down on the surface. But these proteins have a fairly unique chemical group in there. And we call it catechol. And that's... it introduces a type of crosslinking chemistry that you don't get with normal proteins. So what we did going back to trying to make a sustainable adhesive system here, we took some compounds that have some of the chemistry we see in the sea creatures. And we added that to the system.

Anand Jagatia

Well, how did it do in tested performance? Was it as strong as some of the traditional epoxies that people would use in industry?

Jon Wilker

In general, we are getting bond strengths, you know, right, right in league with superglue, and epoxy, sometimes a little bit more, sometimes a little bit less. But pretty much, you know, on par with the traditional petroleum based adhesives. The one thing that we rely on here is we put a lot of heat into the system because that gets the components to react with each other. And so, you know, from a environmental standpoint and carbon impacts kind of standpoint, that might not be the best thing ever.

Anand Jagatia

So speaking of carbon footprint, then I mean, do you have like a rough indication of what the environmental payoff could potentially be if you use this sort of approach?

Jon Wilker

We do have a very rough comparison of carbon footprints here. But lots of caveats here. But just sort of ballpark ideas. If you're going to make, let's say, one tonne of an epoxy, you might end up putting several tons of carbon out into the air with our system, because the plants absorb so much CO2 to form the components that we want. It can, even with the heat that we add into it, you can get the numbers to be actually carbon negative. But again, I want to be really careful about this. I'm not going to hang my hat on that.

Anand Jagatia

No, sure, okay. But a lot of these problems are caused by the fact that the glues are almost too good. And the the bonds are basically permanent. And so you can't take things apart again. So is is the kind of Holy Grail of this sort of research to create a glue that is sustainable, but that can also be reversed?

Jon Wilker

The new adhesive system that's, that's in this paper, we can bond things really strongly. And we also can take things apart. And so So basically, you expose your bonds to water, and they persist for a while, but then eventually they will come apart. A holy grail would be you want to make a bond that is completely impervious to water, and then you snap your fingers. And then it comes apart. That's not so easy. We have not been able to figure out how to do that yet. We're certainly thinking about it.

Anand Jagatia

So what's next, then Jon? Like, what, what are you hoping to do with this formulation, or you can try and improve it? What sort of next for your lab in terms of this specific area of research?

Jon Wilker

Of course, we want to sort of improve the performance. We want to test this under wider ranges of conditions, and also in more specific contexts. That's in the lab. I try to think at least a little bit about outside of the lab, and where are you going to go next, right? And so if we have this promising new system, where could you make the most impact, right? Obviously, sustainability is, you know, hugely important for our future. And there's a lot of barriers we have to getting there. But at least with regard to adhesives, we're hoping that with our work, we're at least reducing the barrier. From the technology side, right, at least we want to be able to provide that part of our move towards sustainability.

Shamini Bundell

That was John Wilker from Purdue University, in the US, speaking to Anand Jagatia. To read the paper, check out the link in the show notes.

Nick Petrić Howe

Coming up, researchers have been trawling a huge dataset to find out how best to tackle childhood malnutrition. Right now though, it's time for the Research Highlights, with Dan Fox.

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Dan Fox

Researchers may have developed a safe and sustainable alternative to a common ingredient in plastics made with a chemical found in wood. The compound Bisphenol A or BPA is used in the manufacturing of various plastics, but it's been linked to a host of human health problems, and its production typically relies on fossil fuels. Now a team of scientists have presented promising alternatives that share the functionality of BPA but lack its adverse health effects. These new compounds are made from a renewable source of lignin, a key component of wood, and when tested, even surpassed BPA in some mechanical properties. Next, the team plans to increase the production scale of these alternatives and optimize the sustainability of their manufacture. Read that research in full in Nature Sustainability.

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Dan Fox

In 1859, a huge flash erupted from the sun. Now researchers have used new tools to estimate this solar flare, known as the Carrington flare could have been twice as bright as any deaths been observed and measured since. Solar flares are local outbursts of energy that cause a region of the Sun surface to emit unusually intense light. They can also be associated with the injection of superheated matter into space. This can generate auroras visible on Earth. Those linked to the Carrington flare are seen as close to the equator as French Polynesia. Now researchers have analyzed detailed eyewitness reports and drawings from to contemporary astronomers who happened to be observing the sun during the event. On the basis of this information, the team estimates that on a modern scale, based on X rays, the flares peak emissions would be around X80 the most intense flair recorded in modern times has been estimated to be X45, at most. You can observe that paper in the Astrophysical Journal Letters.

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Nick Petrić Howe

Next week there is a UN summit in New York. There, high level delegates of governments and stakeholders will be assessing progress that the world has made towards meeting the UN's Sustainable Development Goals. A series of ambitious targets to improve human lives and create a healthier planet by 2030. One of the goals focuses on malnutrition, which affects millions of children worldwide. There are many complicated reasons for this, but poverty and lack of access to suitable nutrition are key factors. The result of such malnutrition is that many children, especially in Sub Saharan Africa and South Asia, are stunted — shorter than they should be — or wasted — they weigh less than they should. These are known as growth failures, and they lead to a higher risk of disease, impaired cognitive development, and even death. There has been some progress towards the UN's target of eliminating stunting and wasting by 2030. For example, studies have shown that children who have just stopped exclusively breastfeeding are at a higher risk of stunting and wasting. And so nutritional interventions have focused on this period, with some success. However, progress towards the UN target is not at a fast enough level, partly because these interventions have been difficult to implement. And the effects have been relatively small. This has led researchers to wonder, are there other periods that could benefit from interventions? Or is there more that we don't know about stunting and wasting. And so they've turned to data, and a lot of it. This week in Nature, a group of researchers are publishing three papers on growth failure in children, I reached out to one of the authors, Andrew Mertens, to find out more. And I asked him what the study's aim to do.

Andrew Mertens

So an exciting part of this research was the ability to aggregate many different existing studies together and try to look for broad patterns across age and across different populations, as well as try to identify more specific patterns about the timing of growth failure, both as measured by wasting, and by stunting.

Nick Petrić Howe

Could you give me an idea of the scale of your study? Because some of the numbers here are quite large.

Andrew Mertens

Yes. So we had about 100,000 children across 33 Total studies. And we had for each child multiple measurements from around birth to around two years of life from about in different countries.

Nick Petrić Howe

Now, I guess is going to be tricky for me to just simply ask, what did you find here? Because there's three different studies to go through. But maybe let's start just with wasting. What did you find with regards to this?

Andrew Mertens

So one of the biggest themes was a surprising finding about how early many children first experience wasting, there have been a paradigm around focusing on the period where a child stops exclusively breastfeeding, because that's the time where you can intervene, identify children are wasting and start offering nutritional support. But one of the things we found was there was a really large proportion of children who are already wasted at birth, or who experienced wasting in the first six months of lives. Many of those children recovered from that specific wasting episode. But those who were born small or experienced early wasting, were at a higher risk of experiencing more wasting and more severe forms of malnutrition, like combined wasting and stunting later in childhood. And they also had an increased risk of mortality.

Nick Petrić Howe

So this surprising very early stage that was important here. And this was kind of mirrored by what you found with stunting, right?

Andrew Mertens

Exactly. Children who are stunted between birth and three months of age accounted for 23% of all the children who experienced stunting by two years of age.

Nick Petrić Howe

So you've shown that stunting and wasting can happen very early in a child's life. But if someone experiences one period of stunting or wasting, does this make it more likely to happen again? Or is this more of a one-time occurrence?

Andrew Mertens

Now, this was not a one-time thing, especially for wasting, which is often thought to be a more acute condition. In fact, we saw repeated episodes of wasting in many children. And so part of this is because wasting and stunting are defined by thresholds. Often you'll see technical recovery from something like wasting where their growth increases above that cut off used to define wasting, but they've been wasted before they're in environments where they may not be getting sufficient nutrition or the It may be a environment with high infectious disease burden, and so they're at a greater risk of experiencing another wasting episode later in childhood stunting, we didn't observe quite as much reversal on stunting. And that aligns with the conception of stunting as a more chronic measure of malnutrition. We saw many children first experiencing stunting earlier in their life. But very few of those children fully recovered from stunting.

Nick Petrić Howe

And one of the interesting things about your studies, you're able to look at sort of trends over time, as well. And you'd mentioned that obviously, very early in life was important for both wasting and stunting. But also, there may have been an aspect of rainfall being important. Can you tell me a little bit about that?

Andrew Mertens

Yes. And it's not necessarily the rainfall directly, but using rainfall as a proxy to define seasonal variation in the different countries where we were aggregating data, it's often a proxy or a hunger season, where in the post-harvest period, food prices might be increasing. And also, in periods of heavy rainfall, there can often be increases in certain seasonal infectious diseases like diarrheal disease patterns, and malaria. And so we saw this really strong pattern where the season of the year was a strong predictor on the proportion of the population that was wasted. And that even affected children in utero. So we saw variations in birth-weight and proportion of children who are wasted across the month of birth. And so for example, in South Asia, we saw that a child born in like May, or June or July, the peak of the monsoon, was on average 0.7 standard deviations below a child who was born in January, based on the international birth standards. And so that's larger than even the most successful treatment interventions, like giving nutritional interventions or interventions to reduce infections.

Nick Petrić Howe

And so the third paper looked at the more sort of causes and consequences of this, what did you find here? Starting with the causes.

Andrew Mertens

So, the risk factors that we found were highest for stunting and wasting were child size at birth, which is not surprising, but we also saw a really strong driver was maternal size. And so that both can directly affect child growth — so there could be direct inner uterine growth faltering among malnourished and smaller stature women, leading to smaller birth size — and it's also a proxy for the intergenerational effects of poverty and malnutrition.

Nick Petrić Howe

And then in terms of the consequences...

Andrew Mertens

So, we found that children who experienced early growth failure had a much higher risk of experiencing growth failure later in childhood, even among those who recovered. And then we also found, regardless on if you're looking at wasting or stunting or a combination thereof, a child experiencing that early in life has a higher risk of dying of the first two years of life. And that risk is increased substantially when a child is both wasted and stunted.

Nick Petrić Howe

And would you be able to give us like a key takeaway message from these three papers? What do you want people to walk away from these three papers, knowing?

Andrew Mertens

A key takeaway is that we may need to intervene earlier, if we're going to make a substantial impact on reducing child growth failure. There are both interventions that we can do today, right now, to reduce growth failure, both in terms of identifying children who have experienced growth failure and giving them supplemental nutrition if they're old enough for it. But also, as mentioned, in seeing the strong seasonality wasting, this may allow us to target specific hunger periods in these different populations, and maybe do preventative nutritional interventions or interventions to reduce infectious disease burden. But beyond this immediate interventions, what we saw is this longer term, intergenerational cycle of poor growth. So it may be we need to start intervening to nutritionally support mothers, even before conception throughout the pregnancy throughout the first two years of a child's life. So both we need to act today, but that this is a long term investment in development and in public health nutrition programs to break the cycle of childhood failure.

Nick Petrić Howe

And so next week, there is a big summit in New York, about the sustainable development goals. At their midway point they're sort of being put under the spotlight. And one of the Sustainable Development Goals focuses on malnutrition and stunting and wasting, and it aims to eliminate it worldwide. How would you say we are progressing towards this goal?

Andrew Mertens

We've made progress but we are not on target to meet the goals by 2030. And so it's going to take continued investment in this and with things like the long term macroeconomic effects of COVID-19 and the effects of the war on Ukraine on global food prices. Now more than ever, we need to continue focus on improving child growth and nutrition in low resource settings.

Nick Petrić Howe

That was Andrew Mertens, from the University of California, Berkeley. For more on this story, look out for a link to the papers in the show notes, where you'll also find links to more of Nature's coverage on efforts to meet the UN Sustainable Development Goals.

Shamini Bundell

Finally, on the show, it's time for the Briefing Chat, where we discuss a couple of stories that we've heard about through the Nature Briefing. So Nick, you go first today, what have you got for me?

Nick Petrić Howe

So, this week, I was reading an article in Nature all about the UK, rejoining Horizon Europe, which is the EU's sort of big research program, and it seems now that researchers from the UK will be able to participate in it.

Shamini Bundell

What's the history of that it was quite a problem that we sort of suddenly left or at least suddenly, from a sort of scientific project point of view, right?

Nick Petrić Howe

Yeah. So I mean, like, I think it's fair to say that a lot of scientists met Brexit with consternation, I would say. They were, there were many worries and uncertainties regarding Brexit. And one of them was whether or not UK scientists will be able to participate in Horizon Europe, which is this huge 100-billion-euro program, which funds all kinds of research across the European Union. And originally, when the UK first left the European Union, when we first Brexited, it seemed like UK scientists, were still going to be able to participate in Horizon Europe, they were still going to be able to apply to get grants, apply to get funding from this program. But then, because of something called the Northern Ireland Protocol, there were some disagreements between the EU and the UK. And that meant that this, whether or not UK scientists can take part in Horizon was left in limbo. And in fact, many researchers who had got funding from Horizon Europe, you know, kind of had to decide whether to move to an EU institution, or whether to cancel that sort of funding.

Nick Petrić Howe

Yeah. So I think I remember some of that. And now it's, I mean, how many years later is this that they've sort of got a new agreement set up?

Nick Petrić Howe

Well it's two years so as you probably remember, in 2020 was when the UK officially left the European Union. But then there was a transitionary year where not a lot actually changed. And then after that point, this is where the sort of disagreements over the Northern Ireland Protocol started to happen. So it's been about two years, since UK scientists have not been able to participate, not be able to get funding from Horizon Europe. And so what's happened is in February, there is something called the Windsor Framework, which is agreement that the EU and UK reached on the sort of delicate situation in Northern Ireland. And with that agreed, it seemed to open up the door for the UK to rejoin Horizon Europe. However, it's taken some months since then for the deal to actually be worked out. And obviously, during this whole long period, scientists have not really known what's been going on and it's made collaborations and whether or not they can get funding for various projects, all those sorts of things, there have been big question marks about them. So I think from reading this article to summarize people's points, there's some relief, but also some sort of annoyance over the fact that it's taken so long, and a lot has been lost in the meantime.

Shamini Bundell

But from now on, is it back to exactly how it was before?

Nick Petrić Howe

No. So, there are some tweaks to it. So it will start in January 2024. So you can't go and apply right now, if you're listening. But soon enough, based on whether the other EU member states actually agree to this as well. But as far as we know, from 2024, researchers should be able to apply for these funds. But the major difference is that there is this sort of 8% threshold. So what the UK has agreed is that it will contribute to Horizon Europe to the tune of 2.4 billion euros every year. But what this 8% threshold is about is that if the amount of grant funding UK researchers win, during a two year period, is more than 8% higher than what the UK is put in, so 8% higher than that 2.4 billion, the government has to sort of pay the excess to the EU. However, if they get 8% less than the money they've put in, then the EU will give that money back to the UK.

Shamini Bundell

Sounds like this is part of the complexities of why it took this long to to come up with this very specific, bespoke agreement for the UK. So this is celebration time for a lot of researchers then I imagine?

Nick Petrić Howe

It certainly seems to be the case. There were a couple of people interviewed for this article, and they seem to be quite happy about the situation. So for example, there was Martin Rees, who's an emeritus astrophysicist at the University of Cambridge who said that "this news will be acclaimed to a rare level of consensus across the scientific community here and on mainland Europe, all have been frustrated by the unconscionable delay in reaching agreements." Others have lamented the sort of damage that has been done in the meantime, Azim Majeed, a primary care and public health researcher at Imperial College said that "leaving the program has caused some damage to UK science. We lost funding, we lost collaborations, and we also lost key contact with EU universities and research groups." Others said "it's fantastic news." And there's a nice quote at the end here from Saurian Bowers, who's head of policy at Wellcome Sanger Institute, they said that "both European and UK science is so much better when it's done together, it's stronger, we produce better outputs. And ultimately, we produce better benefits for European and UK citizens."

Shamini Bundell

That's great, I like the comment on a rare level of consensus among scientists, which sort of leads me on to my next story, a topic on which I don't think there's been terribly much consensus from scientists, but it is about, and I promise I didn't pick it just so I could say this, but it is about mysterious balls.

Nick Petrić Howe

Okay, well, you have to give me more details that just mysterious.

Shamini Bundell

Okay, well, so... it's great, it's great mysteries balls! No, they're called mysterious balls. So, this is a article in science based on a Royal Society, open science paper. And these mysterious balls, which I hadn't heard of before, are basically almost spherical stone artifacts, they would have been made by we think — well, this is part of the controversy — ancient humans. So, you'd find them among sort of like stone tools, like those sort of teardrop shaped blades and things like that. But they've been finding for some time, across the world from his ancient sites, these sorts of stone spheres. They're not like perfectly neat, like weirdly smooth. It's not like how did the ancient people possibly managed to create, you know, these these sort of perfectly spherical objects? But it's more, did they? And why did they create pretty spherical balls made of stone?

Nick Petrić Howe

I mean, I guess when things are this ancient is kind of hard to work out the whys and wherefores. But what is the sort of controversy here? Why are these mysterious balls so controversial?

Shamini Bundell

Well, I guess because they're a mystery. And there are different theories on how they came into being, as it were. So, one theory could be, oh, well, maybe these are sort of naturally occurring. You know, if you think of stones in a riverbed, for example, just sort of like beautifully round, smooth stones eroded by water? Well, these are very different from that, because as I said, they're not this sort of perfectly round smooth surfaces, and also things in Nature very rarely approach, this sort of perfect sphere, that these objects are getting near. Another theory is, well, maybe they're a tool. So maybe there's some sort of percussive tool for banging something. And actually, the fact that they were a sphere has come from this sort of repeated use, they were used over and over again, for some unknown purpose. And that's resulted in this sort of, almost as a side effect, the spherical shape. That's been one theory, another one has just been there, the leftover bits, you've had bits chopped off them, you know, which is known in stone tools, you have the stone tool, and then you have the, you'd often have the core that the stone tool has been made from, which isn't necessarily itself useful, or sort of specifically designed for anything. And then finally, and this is the theory that this particular paper is supporting, the idea that someone has deliberately made these stones into this specific shape. We still don't know why. But this, these researchers have done some work on some particular stone balls from Israel, and done a bunch of analysis and say, you know, we think this was deliberately made like this.

Nick Petrić Howe

Well, lay out their argument for me, why is it that they believe that these were definitely made for some sort of odd purpose?

Shamini Bundell

Yeah, so this is a team of scientists from the Computational Archeology Laboratory of the Hebrew University of Jerusalem. So, we're gonna get into some computational archaeology techniques. And this is actually a site in Israel, where they have found, over the sort of different layers that this site represents, hundreds of these sort of stone balls have different levels of sort of sphericalness, I suppose. You know, some of them are really approaching a true sphere, some of them are a bit janky. No one knows whether they are all the same thing, whether they're actually differences are they sort of part of a sequence where one is being turned into the other? So what these folks did is basically take 3D scans of some of these sort of spheroids, they call them, so 150 spheroids made of limestone from this site, and they use these sort of 3D scans to to measure things like the surface curvature, the center of mass, the sort of angle of the different sort of edges that have been made. And what all that tells you is, basically, they're looking at the patterns of the shape, the angle, the surface, and trying to work out from that okay, how was this made, how was this particular shape and patterns and being cut off, there formed? And they argue that it's unlikely to have been created by natural processes. And it bears the hallmarks of intentional craft work. And they suggest that each of these objects started off with a sort of primary removal of like a big flake of stone. And then once you've got that big sort of flat flake that's been removed, then smaller chipping away at the edges to kind of curve that round. And what they also argue — they don't propose a purpose for these, although my mind does, sort of going off into all sorts of exciting ideas about why you'd want balls — but what they say is interesting for these sort of like 1.4 million year old hominins of that time, is that they would have needed to have therefore this ability to conceptualize a sphere, and then shape the stone in their hand to match that. And also, they say, it suggests an appreciation for symmetry and beauty in creating this form. Perhaps again, if we knew a bit more about what they were for, that could change, but maybe it is just about creating, creating this piece of art, we're not sure.

Nick Petrić Howe

And so how is this new analysis of these balls being met by other researchers? Do they think this is a likely scenario? Or are there still doubts?

Shamini Bundell

So, there was one scientist quoted in this article who was a little bit skeptical. And one of the reasons why is because, you know, she says, the researchers haven't really separated out different kinds of objects that might actually represent different stages of the manufacturing process. So some of the less spherical ones, maybe they're objects that just sort of got abandoned halfway through. So by lumping them all together, you might be sort of missing some sort of important information there. Another researcher was sort of focusing more on the methods that they used. So she called them "a valuable tool" and wants to see these kind of things applied to other old artifacts, even more ancient spheroids have been discovered in Africa. And people could use this 3D scanning method there as well.

Nick Petrić Howe

Well, if I can play the wild speculation game, the thing I see humans using spherical objects most for these days is for fun for balls and things like that. So I reckon that's what it is. I'll write my paper.

Shamini Bundell

I was wondering whether you'd want to make them out of stone. You wouldn't want to be kicking or throwing them, maybe like a boules type game where they have to land in the sand at a certain point.

Nick Petrić Howe

Yeah, I reckon. I reckon that's it. I reckon. That's it. I will submit my manuscript soon. But thanks Shamini I think that's super interesting. But that's all we've got time for this week on the Briefing Chat. Listeners, if either of those stories have caught your attention, then you can find links to them in the show notes. And while you're there, you'll also find a link to where you can sign up to the Nature briefing where you can get more stories just like them direct to your inbox.

Shamini Bundell

Well, that's all for this week. But as always, you can keep in touch with us on X where we're @naturepodcast, or you can send an email to podcast@nature.com I'm Shamini Bundell.

Nick Petrić Howe

And I'm Nick Petrić Howe. Thanks for listening.