Cervical screening self swabs, and jelly-based batteries
In this edition of The Naked Scientists: Self-test kits to help doctors bear down on cervical cancer; the ‘jelly’ batteries that could be used in wearable tech devices; and why seagulls keep trying to steal your chips, and how to stop them: science has the solution!
In this episode
01:00 - Self-test success for cervical cancer swabs
Self-test success for cervical cancer swabs
Anita Lim, King's College London
Researchers at King’s College London have estimated that more than one million extra women could have life-saving cervical-cancer checks if the NHS adopted do-it-yourself testing. The team say the results of their self-testing trial - which uses swabs for lab analysis - has been a “fantastic” success. Here’s the study’s author, Anita Lim…
Anita - We know that cervical cancer is caused almost entirely by something called the human papillomavirus. And this is a virus that is very, very common. Most people in their lifetimes will have it, but in a really small proportion of people who have it, the infection will stick around and it will start to make changes on the cells of their cervix, which is the neck of the womb that can develop into a precancerous lesion. And it's really easy to remove and treat those and prevent cervical cancer from even developing. And that's what we use screening for.
Chris - And so the argument would be that if you remove as many barriers as possible to a person getting screened, so you maximise the uptake, you're going to maximise the detection early and therefore get more pickup, more early intervention, more cure.
Anita - Exactly. The numbers of people who've been coming for cervical screening has been falling and they've been falling for the last 20 years. And we know that a lot of the reason why people don't come for their cervical screening is because it's a really intimate test. So people quite often might find it painful or they might be worried about developing cancer or they might just be feeling really embarrassed to have it. Some people are just busy, they plan on going to get their screening and they just don't get round to it. And then there's also simple things like people just not even realising that they need to get screened. If you're not getting screened regularly, you're not getting that chance to go and pick up what is such a preventable cancer. And allowing people, giving people the choice and the convenience of being able to take a sample themselves and the privacy of their own homes. It's just completely game changing for cervical screening as we currently know it.
Chris - What was the overriding question that you were hoping to probe with the study?
Anita - We wanted to see if self sampling, if we did offer it to those people who weren't coming, how many more women could we actually get screened by offering them the opportunity to do that. We offered over 27,000 kits to people with a cervix. And we did this in two different ways. We offered it at GP practices, so we got GPs and nurses and healthcare practitioners to offer kits to women who were overdue for screening when they went into the GP practice for any reason. The other way that we got kits out to people is we mailed kits to people's homes directly. And what we found was that if you offer the kits at the GP practice, we found that 56% of people who hadn't come to their screening before would actually return a sample. And when you mail them to people's homes, 13% of people would return a kit. And based on this data, what we estimate is that you could get over a million extra additional women screened if this was to be rolled out over England more widely over one screening round.
Chris - And based on what we know about the prevalence of human papillomavirus, HPV that causes cervical cancer, and the number of cases of cervical cancer that are occurring, how many cancers do you think you can prevent with an intervention like this each year?
Anita - It's very difficult to actually estimate that number based on the type of study that we did. And one of the reasons for that is because this is a sort of cancer that develops over, over a 10 year period or so. So it's quite difficult to estimate based on the study that we did. But what we do know is that because screening is so protective against cervical cancer, we do know that by introducing something like this, it's very, very promising. It's very likely that we will be saving many lives.
Chris - One of the criticisms of self sampling that doctors have raised in the past is whether or not you get adequate samples, whether people do it as well as a healthcare professional to get meaningful data. So were you finding that the samples that were coming back to you were good enough quality for you to give a negative or a positive that really meant something?
Anita - 99 out of a hundred women can take that cell sample correctly and that will take it accurately and that you can rely on the result. And then the other way to think about accuracy, and I think this is probably what you are trying to get at here, is around whenever you do a test, you're trying to pick up something and the evidence for self sampling is very, very robust. So the important thing to know about this is that if you take a self sample and your result is HPV negative, you can be just as reassured because that is just as accurate as the same result on a sample that would have been taken by your doctor or nurse. But if you take a self sample and you test HPV positive, this is just a preliminary indicator and you would need to have a follow-up test with your GP or nurse, which would be the conventional screening test. And this is just because you don't collect cells from the cervix as part of the self sample test. And so you just need an additional step in order to tell you if you need to go and have additional tests with a gynaecologist.
Chris - Does this suggest, based on what you are finding, that in fact our gold standard for initial screening should be to just invite women to self screen and only escalate their cases when you pick up a positive along the lines that we've been discussing?
Anita - My personal view on this at the moment is that we aren't ready for that yet. Self sampling isn't going to be for everyone. And what I would see for now or the next few years is certainly that we are going to see both tests alongside each other and having the choice will allow us to really increase the uptake of screening participation.
07:07 - Jelly-based battery for brain implants
Jelly-based battery for brain implants
Stephen O'Neill, University of Cambridge
Researchers at the University of Cambridge have developed soft, stretchable batteries that are based on a jelly-like substance that could be used in wearable devices, soft robotics, or even implanted in the brain to power implants to treat conditions like epilepsy or depression. The bendy batteries work by using special polymers full of holes that can be filled up with charged particles, which generate a current when they flow from one polymer layer to the other. I went to meet Stephen O’Neill who is working on the project as part of his PhD at the Melville Laboratory for Polymer Synthesis at the University of Cambridge…
Stephen - So what we're trying to do is make a soft and squishy power source or a battery, and this is to be able to interface with tissues in our brain or anywhere in our bodies where the materials aren't stiff and rigid, like your typical batteries in your phone or your laptop. And this will allow the body to really take it in and stop the body from rejecting these devices because they're soft and squidgy and have a lot of water just like our brains do.
Chris - That's an issue though, isn't it? To a certain extent these things are stiff and rigid in order to give them the properties they've got and store lots of energy. So you're almost trying to reinvent the wheel here.
Stephen - Yeah, exactly. That's true. So your typical things that conduct electricity or conduct electrons are metal or silicon. And these can conduct electrons because they're so stiff, electrons can flow across them. Whereas it's very difficult to make them soft and still conduct electrons. So what we've done here is we've made hydrogels, we've put polymers, dissolved them in water and tried to make these polymers charged to be able to conduct charge or conduct electricity.
Chris - And is that what you brought along? Because you've got this enticing looking Petri dish here <laugh> Stephen, with this blue stuff in it. What's that?
Stephen - Yeah, so I brought along one of the hydrogels and it's very soft and stretchable, almost like the jelly that people might know and actually eat. And we can stretch it to large amounts, actually over 10 times. Its initial strain, very flowable and movable.
Chris - And that is a mixture of those polymers you're talking about that you've given a charge to. And are they stretched out in there almost like mini wires within the jelly then? Is that how that works?
Stephen -
Yeah, exactly. It's kind of like you can imagine a 3D network of wires in water. So about 60% of it is water and the other 40% is these wires that are stretched out and connected to each other in kind of a 3D network in that water. And these are charged.
Chris - And how does that actually store charge then, if you've got these charged particles? Because I could say, well, salt has got sodium and chloride in it and they're charged particles. Doesn't store electricity though. So how does this actually store the charge and how does it then discharge?
Stephen - What we have is we have salt within these gels and we have numerous compartments of the gels that we stick together. And some parts have lots of salts in them, and other parts have very low amounts of salts in them. And when we put two of these together, one hydrogel with high salts and one with low salts, the salts actually start flowing from the high to the low in a process that's called diffusion. So they kind of balance out the salts in the gels. Now if we, in between, we put something that can only let positive salts go through because salts usually are made up of positive and negative ions. For example, table salt is sodium chloride, the sodium is positive and the chloride is negative. So if we put something in between these two gels that will only let the sodium go through. Then on one we'll have a lot of sodium flowing from one side to the other and we'll get a buildup of these positive sodium salts just on one side and it will leave negative chloride salts on the other side. And this charge difference is really where we're getting this voltage.
Chris - And how do you charge the battery? How do you force the ions to have that disequilibrium in the first place?
Stephen - Yeah, so to be able to recharge the battery, we have to force them back over by applying a higher voltage. So that will be a recharging process and that's not that favourable, so we have to recharge it with another battery.
Chris - The breakthrough here then, from what you're saying is you've had to come up with the recipe for these polymers that have these gaps in them that will accommodate the charged particles. And then you've got to have the right sort of membrane to separate them. That will exclude charge that's minus, and just allow charge that's positive to go through. So you've had to solve a sort of materials problem as well as an electrical problem. Does it work?
Stephen - So yeah, good question. Yeah, it does work. So we do get a voltage out of it. So we're getting about 0.1 volts per unit cell, which is less than the batteries you'd buy in, in the shop, for example. But one way to increase this voltage is by putting a lot of these batteries in series, so one after the other. And that increases the overall voltage that we get from these power sources.
Chris - And does it tolerate lots of charging and recharging? Because that's the other question, isn't it? If your battery collapses out in 10 minutes, it's totally inconvenient. Whereas if it'll keep being charged and discharged for a long period of time, it makes it much more useful.
Stephen - Yeah, that's definitely one of the next steps that we really need to look into, so how many cycles can this go through? And whether the source can go back and forth, reversible over many cycles. And I think that will be a key milestone for really translating this into real implantable applications.
Chris - And will all the batteries be that sexy blue colour or <laugh>? I mean, why is it blue?
Stephen - This is blue for the cameras. Naturally they're transparent, but we use food dye to make them blue.
Chris - So I could have a battery of any colour I want. Then it's like a model T Ford. Any colour that you like, as long as it's black, yours don't just have to be blue. You can have green ones. Pink ones. Yeah.
Stephen - Fully customisable. Your favourite colour. We can do, yeah.
Chris - That sounds like a marketeer's dream. <laugh>.
Stephen - Yeah, <laugh>. Sadly you can't see it if it's in your brain, but anyway, you'll know it's blue.
14:24 - Sun hitting peak sunspot activity
Sun hitting peak sunspot activity
Ryan French, National Solar Observatory
Over recent weeks and months, the Sun has been extremely active. It has not only excited physicists and cosmologists, but it’s also meant that the northern and southern lights have been visible at far lower latitudes than normal with people posting dramatic images from their neighbourhoods on social media. But just how unusual is this intense period of solar activity? Ryan French is a physicist at the National Solar Observatory, and author of 'The Sun: Beginner's guide to our local star’...
Ryan - So the Sun at the moment is entering this period we call solar maximum. The Sun follows an 11 year cycle of increasing and decreasing activity on the Sun. At the bottom of this cycle, there are no solar flares, no sunspots, no eruptions on the Sun. But at the moment, at this point, sort of last year into this year, through to next year, we're in this phase of solar maximum where there are lots of flares, lots of eruptions, and so you're likely seeing a lot of new stories because of that.
Chris - So we define the Sun's cycle in its activity by the presence of these flares and sunspots and so on. They're the kind of visible manifestation that the Sun is behaving differently?
Ryan - That's correct, yes. So sunspot specifically, there are these dark structures on the Sun. This is where flares and eruptions originate from these sunspot regions. So the solar cycle is literally just defined by counting the number of sunspots on the Sun every day. And that count follows this nice 11 year cycle.
Chris - And how far back do records go?
Ryan - They go back all the way to the 1700s. Back then they weren't counting sunspots as we are now. The official count didn't start until the mid 1800s, but right now we are in solar cycle 25. So if you multiply 25 by 11, that takes you back way into the 1800s.
Chris - And are there any other changes apart from these sunspots and the flares and so on, which perhaps we'll come to in a second. Are there any other changes in how the Sun behaves when it goes through this 11 year cycle?
Ryan - So there's a few different changes, but they're all kind of interconnected. So the total brightness of the Sun varies very slightly throughout this period. The magnetic field of the Sun actually flips throughout this 11 year solar cycle and the complexity of the magnetic field in the Sun's atmosphere, which does cause all these flares and exciting events, varies a lot too.
Chris - And how do those flares when one happens? How do they affect us?
Ryan - Yeah, so solar flares can affect us in a couple of key different ways. The first of all is from the flare itself. So a solar flare is just a conversion of energy from the magnetic field of the Sun into primarily light, mostly X-rays. And when those x-rays are produced from these solar flares, they can hit the upper atmosphere of the Earth. That can expand the upper atmosphere slightly. This can cause a sort of what we call radio blackout. So radio waves cannot propagate quite as well. Communication to satellites doesn't work quite as effectively. But the second probably more crucial element of these flares is not the flare itself, but about half of solar flares, a coronal mass ejection, which just a bunch of stuff from the Sun launches out into space. And if that arrives at Earth, it not only produces beautiful Northern Lights displays like we saw earlier this year back in May, but that also has the ability to impact the power grid and satellites as well.
Chris - So it's pretty important that we monitor it because of the impact on us that that could have. Is that becoming more common or are these events when they occur intensifying?
Ryan - Yeah, that's a great question. Certainly it is very important for us to understand these events, and there's a massive global effort worldwide to try and improve our understanding both at the Sun and when it arrives at Earth. At the end of the day, there's nothing unusual going on at the moment. We're entering this phase of solar maximum, as I said before. So these events are more common. As events are more common, there are higher chances of very, very big events. The one in May, for example, was the biggest event that we'd had for 20 years or so. And that's a pattern across all of these phenomena. Actually, this solar cycle that is peaking at the moment is already bigger than the previous solar cycle that peaked back in 2014 or so and more in line with solar cycles that peaked back in 2003 and beforehand as well.
Chris - So do you think then that although we've got this 11 year cycle superimposed on that, or at least that could be superimposed on a bigger cycle, which is that gradually these things increase over time, perhaps cyclically and that we're going to see even more intense activity in the years ahead?
Ryan - It's quite possible. We do think that these solar cycles might be imposed by a greater cycle, as you said. But, we're just coming out of the very minimum of that sort of second grander cycle, we believe. So the highest solar activities we've ever measured were actually back in the 1970s and 80s, and we're still way away from the levels observed during that period, even though we are now more active than we were a decade ago.
19:39 - Why do seagulls steal fish and chips?
Why do seagulls steal fish and chips?
Neeltje Boogert, University of Exeter
Have you ever wondered why seagulls dive-bomb holidaymakers for their fish and chips? Well, it turns out that researchers at the University of Exeter may have found the answer. They conducted an experiment on 27 herring gull chicks in Cornwall, and discovered that they almost always prefer seafood even when multiple other food alternatives, including those they’ve been reared on, are on offer. Here’s Neeltje Boogert at the University of Exeter…
Neeltje - So the big question is how do gulls come up with this idea of stealing our food? We know that adults are very good at it. We also know that juveniles are not so good at it. And so we are just wondering, is this something that they learn from adults? So if you have gulls living in cities does that mean that their chicks will also become food stealers or is this something that they learn later on in life?
Chris - Nature versus nurture, that old chestnut.
Neeltje - Exactly, yes. Because we really don't have any idea how they acquire these skills.
Chris - And so how have you been able to look at this? Because these are protected, these species that you are interested in, aren't they?
Neeltje - Yes, exactly. Although we studied herring gulls in particular in different countries, there'll be other species that are more common. Actually they're in a national decline, which basically means they are in fewer numbers breeding on their natural sea cliffs. But actually they're really increasing in towns.
Chris - So it might be that they're not decreasing, they're just decreasing where we are looking.
Neeltje - Well, exactly. It's just really hard to count numbers in towns because I don't know if you've seen them around where you are. But they often build nests next to chimneys and on flat roofs, on industrial estates. So you would need some kind of expansive drone survey. Whereas on natural sea cliffs you can just kind of sit there with binoculars and count all the nests. So I don't think there's a very systematic assessment of exactly how many breeding pairs are in towns. But our impression is that they are increasing. However, we don't know exactly what happens to the offspring. So if you breed in town, do you then have chicks that thrive or they're actually not doing particularly well? That's another question we'd like to investigate.
Chris - And also presumably understanding in order to do better conservation. What's driving that potential invasion of the city? Is it that they're in pursuit of a ready meal, which comes more easily in town than it does on the cliffs by the beach?
Neeltje - Yes, exactly. So we don't know whether it is that towns just attract particularly bold individuals. So if you're a risk-taking individual and just not averse to stealing, maybe you're attracted to towns. Or the question that we're trying to address in this study was, if your parents are food stealers, will you actually become a food stealer yourself?
Chris - And how did you ask that question?
Neeltje - So what happens around here in Cornwall is that birds will breed on roofs and then once the chicks are ready to fletch, or perhaps before then, some of them fall off roofs. And so what happens then is that people will take them to rehabilitation centres to allow them to grow up in captivity. And so we got 27 of these chicks that have fallen off residential roofs in towns across Cornwall, and then we rear them on different diets. So we are trying to replicate the extremes that we see in nature where some parents might feed their chicks, mostly fish and marine foods and other parents might feed their chicks mostly urban foods. So we're trying to replicate this natural scenario.
Chris - I'm desperate to ask, what's urban food? Does that mean burgers, chips, <laugh> junk food?
Neeltje - <laugh>. That is an excellent question. So due to animal welfare and ethical concerns, we weren't inclined to feed them like the worst of anthropogenic foods. So while we settled on then it was mostly cat food and bread. And then we added some supplements, vitamins and things to make sure that they actually were offered nutritional quality as compared to the marine foods. Because we don't wanna create, you know, awful health issues in these birds, but we presented them with the kind of thing that they might encounter in urban areas. And so the funny thing is actually that in my house, our kitchen door is being visited every day by a gull that comes tapping on the glass. And then one day the door was open and it actually went for the cat food bowl. So they <laugh> they're definitely aware of these kinds of food sources, but in general, what you of course see in towns is that they'll steal your chips and your pasties, if you sit around with carrots on the beach, they will not go for that. So they are picky in what they eat. For sure.
Chris - And the question then is having reared them on one food stuff, does that become their preference? It's a sort of learned thing or do they still revert to type given half the chance?
Neeltje - So that's exactly the question we tried to address. So what we had done, how we manipulated this was that, because you might also see that they're just preferring what they're most familiar with. So what we did is all birds got all foods throughout their stay in captivity. You can actually hear them in the background now. But 80% of the time they would've marine foods in a marine treatment group and 20% of the time they would have urban foods. And in the urban food treatments it was the opposite. So 80% of the time they would've cat food and bread and 20% of the time they would've fish. So everyone had seen the food throughout their stay in captivity. And then four times in their early life we tested them on which food they preferred. And it turns out that actually it really doesn't matter what you feed them in early life. They just love fish. So you can try to give them cat food or bread most of the time. And when they're little chicks and they will always go for fish, they really do not like bread or cat food. So in other words, urban birds, if they were feeding their chicks or trying to feed their chicks, a lot of human foods, they'll probably reject it and we'll just go for the fish.
Can we get DNA out of fossils?
Thanks to Jack Lovegrove for the answer!
James - Can you extract DNA from fossils? Thanks, Phil. You've struck upon the fabulous field of ancient DNA. To help me answer your question. We put in a call to Jack Lovegrove at the Natural History Museum
Jack - For the majority of fossils, the answer is no. Traditionally, when we think of fossils, we are thinking of things that are many million years old. As the fossil is trapped in the sediment and the sediment is squished down and lithified turned to rock, pore waters get into the fossil and replace the original bone with different minerals, and the bone is remineralised, in effect, turned into stone. However, we now have been able to extract DNA from some of the most recent fossils. So the oldest DNA that's been extracted directly from a fossil comes from just over a million years ago, which was from a mammoth tooth that was found in the permafrost. The actual oldest DNA that's been extracted from anywhere comes not directly from a fossil, but from the sediment itself. And that's from a site in Greenland and about 2 million years old.
James - That's interesting. So some of that biological material preserves for millions of years. Life on Earth though, as we know, has been going on for tens and hundreds of millions of years. What's the limiting factor to DNA hanging around for longer, perhaps? Is it, as Paul suggests on our forum, DNA is strung together by means of phosphate ether bonds, which are not the most stable of chemical bonds.
Jack - Paul is right. I'd say there are two main limiting factors, and one of them is that DNA is not a very robust molecule compared to some other organic molecules and organic components of living things. So for example, there have been some controversial studies that have reported finding tiny traces of organic material from much older fossils. So even up to about 190 million years old. But even then, they're not talking about DNA. They're talking about very degraded remnants of collagen and maybe individual amino acids. It's been suggested, have been found in egg shells, but not DNA because it does fall apart. And the second reason that we don't find DNA is that most fossils have been remineralised. So all the organic material has been replaced with inorganic minerals.
James - Your specialty at the Natural History Museum is dinosaurs. It's bad news for those who are helping one day, we might uncover dinosaur DNA. Or is it?
Jack - In terms of non-bird dinosaurs, I would say it's very unlikely we're going to get DNA from their fossils. Sort of last of the non-bird dinosaurs, things like triceratops, that's about 66 million years ago. And then the stuff I work on, the earliest dinosaurs, you're looking at at least 240 million years ago. So sort of an order of magnitude out.
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