Chemistry World Podcast - September 2008
00:10 -- Introduction
02:06 -- Could cancer be diagnosed by smell?
04:32 -- Lighting up cancer with fluorescent imaging to aid surgery
07:05 -- Nancy Rabalais from the Louisiana Universities Marine Consortium talks about the growing problem of ocean dead zones
14:30 -- A stretchy conductor that could be made into robot skin
16:50 -- An electronic tongue that can tell if your Beaujolais is bogus
19:38 -- Richard Van Noorden explains how a new water-splitting catalyst could be the start of a solar energy revolution
24:46 -- Can stained glass windows purify church air?
26:53 -- Chillies get hot to keep fungi away`
29:45 -- The answer to last month's chemistry conundrum and an old-fashioned yet seasonal question
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
(00:10 -- Introduction)
Interviewer - Chris Smith
Hello! Welcome to the Chemistry World Podcast with Victoria Gill, Richard Van Noorden, and Fred Campbell. I'm Chris Smith. Coming up, why researchers are raising a glass to a new gadget that could be used to combat food fraud.
Interviewee - Victoria Gill
It's a tiny little sensor that acts as an electronic tongue; it's very portable and can be made quite cheaply and it can tell you the grape varieties and even the different vintages of wine. It can tell the difference between the different types of wine.
Interviewer - Chris Smith
Victoriawill be sniffing out that story shortly. Also, why the fishing forecast meanwhile isn't looking so good for the Gulf of Mexico.
Interviewee - Nancy Rabalais
And the Gulf of Mexico, every spring through fall, we have an area in the shallower waters where most of the oxygen goes away in the bottom waters and you have an area up to 22,000 square kilometres that you cannot catch any fish that normally live on the bottom or shrimp or crabs.
Interviewer - Chris Smith
Nancy Rabalais would be joining us to talk about the worsening phenomenon of ocean dead zones. But when it comes to cleaning up our environmental act, have scientists stumbled upon a heaven sense solution to the problem of air pollution.
Interviewee - Fred Campbell
This is research that comes out of the Queensland University of Technology from a guy called professor Zhu and what he has found is that stained glass windows is painted with gold paint has to contain nanoparticles of gold within the paint; what that can do when the sun shines on it, they become catalytic reactive through this photoactivity and are able to then decompose volatile organic compounds that are in the air.
Interviewer - Chris Smith
That's why churches are worth their weight in gold and that's coming up later in the program. And we'll also be finding out the answer to this month's chemical conundrum.
Interviewee - Richard Van Noorden
Which world renowned chemist synthesized the molecular version of the Olympic rings?
Interviewer - Chris Smith
And if you sent in a solution then keep listening to find out if you one of this months' winners.
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The Chemistry World podcast is brought to you by the Royal Society of Chemistry. Look us up online at chemistryworld dot org
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(2:06 - Could cancer be diagnosed by smell?)
Interviewer - Chris Smith
Cancers claim the lives of one in three of us and skin cancers specifically are one of the fastest growing causes of death amongst western countries, but now researchers might have a new tool at their disposal to help us sniff out the problem a lot sooner, Victoria.
Interviewee - Victoria Gill
Yeah, this is a research that's come out of the Monell Chemical Senses Center in Philadelphia which is a fascinating place and researchers were inspired by the fact that dogs can actually detect the compounds, can smell the compounds in certain types of cancer. They can smell lung cancer on sufferer's breath for example.
Interviewer - Chris Smith
But what are they actually smelling?
Interviewee - Victoria Gill
They are smelling compounds that are specifically sort of up-regulated in cancerous tissue. So the researchers tested this in skin cancer and they have found that skin cancer does have its own, sort of, smell fingerprints. So they are doing very, very simple tasks where they put an absorbent wick inside a glass tube. The whole set up looks kind of like that old-fashioned cupping medical procedure, where you are sort of blister a person's skin. So you put the glass tube over the skin with the absorbent wick inside and you actually absorb the compounds that are there in the air around the piece of tissue that is suspected of being cancerous and they found that yes indeed it has higher levels of certain chemicals than in healthy tissue and they have also tested by swabbing the area with alcohol to absorb the chemicals that are actually on the skin and that has its own fingerprint as well.
Interviewer - Chris Smith
So this is presumably some kind of diagnostic strategy that instead of having to do physical biopsies on people, you could get an idea as to who might need a biopsy better by doing this.
Interviewee - Victoria Gill
Yeah, with a really simple and very quick test and the strange thing is that they don't know why, they don't know what biochemical mechanism is taking place that's giving this cancerous tissue, this particular odour, but it does seem to work. They tested it on humans and they've had 11 people that do have confirmed skin cancer and 11 healthy people and they've confirmed that these fingerprints are actually diagnostics. So they'll probably be able to take it further into the clinic before finding out why it actually works.
Interviewer - Chris Smith
The bottom line here is that they actually want to try doing this or is it just early days, when can we start seeing this in the clinic?
Interviewee - Victoria Gill
Well they're hoping to be able to develop this into a diagnostic test, yes, but they are also going to study more about the biochemistry that's happening inside the tissue to find out why it's making these particular compounds, because I mean that might be able to tell you more about the actual mechanism of the cancer as well and the progress of the cancer.
(4:32 - Lighting up cancer with fluorescent imaging to aid surgery)
Interviewer - Chris Smith
So keep your nose peeled for that one and Fred, this is interesting, sticking with the subject of cancers. There's also a way now of making cancers glow up, so that researchers and doctors can spot them and know where they should direct their scalpel.
Interviewee - Fred Campbell
Yeah, this has come out of the John Frangioni's Lab in Harvard and what they have come up with is a non-invasive technology for imaging of cancer cells that gives the doctor essentially a real-time image on just a standard computer screen, where the cancer lies so that he can just work around the cancerous tissue with the knife and he gets a much more accurate picture of where the cancer actually is.
Interviewer - Chris Smith
How does it work?
Interviewee - Fred Campbell
It works through a technique called near-infrared fluorescence and what that means is essentially they inject a radioactive label into the human and then they follow that with the dye that's actually the fluorophore that can be sensed by the spectrometer and what they get is then a near-infrared image which isn't immediately a, sort of, pickable to human eyes and therefore they overlay that with another image just a standard digital image of the limb and overlaid what they get is the exact, sort of, representation of where the cancer is in the human.
Interviewer - Chris Smith
Why do you need the radioactive material, why can't you just use the original marker that gives you the infra-red?
Interviewee - Fred Campbell
This is the problem with the research and in fact what's being reported here is that this is going into clinical trials, what they are actually trying to do is to create labels that don't involve a radioactive tag on them that can specifically target malignant cancer cells over benign cancer cells. So at the moment the clinical trials are using the radioactive label to excite the dye so that they can view it through near-infrared, but what they ultimately want to do is to make a label which does not have a radioactive tag.
Interviewer - Chris Smith
So is it the radioactive label that's going just to the cancer and the dye goes everywhere, or is it dye just going to the cancer and the radioactivity goes everywhere.
Interviewee - Fred Campbell
The radioactivity goes to the cancerous cells and then it excites the dye around the cells so that they can then image it through this near-infrared.
Interviewer - Chris Smith
And this presumably shows surgeons and doctors where to, what target radiotherapy or where to actually cut.
Interviewee - Fred Campbell
Traditional techniques have involved a similar, sort of, radioactive tag and a dye that isn't near-infrared active and what they do then is they sort of visualize with their eyes where this dye is and when it is mixed with blood, it becomes very difficult to tell actually where this cancerous tissue is. So this technology gives them a much more accurate picture and a much more bright and vibrant picture of where the cancer is, so that they can be more accurate in cutting the cancer out.
Interviewer - Chris Smith
Any kind of cancer or there are specific subtypes that this is for?
Interviewee - Fred Campbell
They are specifically concentrating on breast cancer at the moment, but they have shown that it can be applicable to other cancers. So at the moment they're concentrating on breast cancers and that's what the clinical trials are.
Interviewer - Chris Smith
Thanks Fred, so two very encouraging developments in the battle against cancer.
(7:05 - Nancy Rabalais from the Louisiana Universities Marine Consortium talks about the growing problem of ocean dead zones)
Interviewer - Chris Smith
Less encouraging though is the situation in the Gulf of Mexico and also around the mouths of the other major estuaries around the world where fertilizers are washing off the land and turning the sea into an oxygen devoid dead zone. Nancy Rabalais who is based in Louisiana has been studying the problem.
Interviewee - Nancy Rabalais
Well in the Gulf of Mexico every spring through fall, we have an area in the shallower waters out to about 30 meters deep where most of the oxygen goes away in the bottom waters and the lower part of the water column and when that happens those fish and shrimp and crabs that can move out of the area will migrate out of the area if the oxygen falls below a level of 2 mg/L or parts per million. Those organisms that can't move they start to die off. So you have an impoverished fauna that live in the sediments; you've got loss of biodiversity; and you have an area up to 22,000 square kilometres that you cannot catch any fish that normally live on the bottom or shrimp or crabs.
Interviewer - Chris Smith
Well that's a massive area, isn't it? Where does the oxygen go?
Interviewee - Nancy Rabalais
Basically, you have to have a stratified water column which means you have to have differences in salinity and temperature that create layers in the water column and in the Northern Gulf of Mexico we have a huge amount of fresh water coming from the Mississippi river and that has a tendency to stay on the surface and the saltier water stays on the bottom. So that gives the physical structure that supports the development of hypoxia or low oxygen and sometimes called the dead zone because you can't catch any fish. At the same time, the river brings in a lot of nutrients, nitrogen, phosphorous, that stimulate the growth of the microscopic algae, the phytoplankton, which are normally and are the base of the food web. They feed the zooplankton, the smaller plankton, the smaller fish and then eventually up to the top of the food web to the larger predators, but there are so many nutrients, nitrogen and phosphorus in particular that are coming in to the Gulf of Mexico now that the amount of small phytoplankton that grow is just way over the amount that the other organism can incorporate it into the food web. So that material sinks to the bottom and bacteria that live in the bottom in the sediments, basically live off of that organic carbon that comes from the detritus from the surface waters and they use up oxygen in the process of decomposing that carbon. So what happens when there is a stratified system, the oxygen that's normally in the surface waters does not diffuse or move slowly from the surface to the bottom, because that layered system creates a barrier and at the same time, the bacteria are basically consuming all of the oxygen. So, you end up with an oxygen deficit or less oxygen than you would normally have and that's what leads to this low oxygen area.
Interviewer - Chris Smith
Are the scale of these dead zone areas increasing, are they getting bigger?
Interviewee - Nancy Rabalais
Certainly in the Gulf of Mexico, the area has gotten larger; in the first 5 or 7 years that we measured it, it was on the range of about 9000 sq km. And now it is on the average of about 19,000 sq km. and the oxygen levels have probably gotten lower.
Interviewer - Chris Smith
The thing is this phenomenon isn't just in the Gulf of Mexico, is it? If we look around the coast of a number of countries, where there are big estuaries opening into the sea, you see the same phenomenon.
Interviewee - Nancy Rabalais
The areas around the globe number more than 400 now and two scientists Robert Diaz and Rutger Rosenberg just published an article in Science magazine documenting the increase over time and there's basically been a doubling of these low oxygen areas since the 1980s. Mostly, industrialized nations with a lot of agriculture and a large human population, are the places where these low oxygen areas have occurred in the past. In the United States the largest one of course is the area off of the Mississippi, off of the Louisiana coast, Chesapeake Bay over 50% of the US estuaries have these low oxygen conditions at sometime during the year, so that's a large area. The future is now because many of the areas around the world that are starting to be industrialized, starting to have the green revolution and more fertilizers applied to the soil are now beginning to have these low oxygen areas where they didn't have them previously, so the prediction is worsening of those that already exist and then there will be even more in the future.
Interviewer - Chris Smith
Now you mentioned that the animals that are exposed to these conditions that can move do, the ones that are left behind perish, all sorts of animals are perishing and what's the scale of the problem. Are we seeing knock-on effects in the ecosystem because of this?
Interviewee - Nancy Rabalais
Well, the ones that remain in the sediments are the worms, the snails, the clans, the starfish, but those form the community that makes the organisms in the bottom sediments and this is what the fish and the shrimp and everything else that needs to feed there, that's what they feed on. So when the oxygen falls really low for extended periods of time, a lot of that material is just dead, it dies and that means that the biomass, the amount of food available for organisms that come back in the fall after the low oxygen conditions are alleviated by winter storms, they don't have as much food to eat. So that has implications for overall production of the system. The other thing that has happened is that these animals that remain are very small, they live near the surface of the sediments and they don't do "normal things" that benthic animals those that live in the sediments need to do like, build deep burrows and irrigate the sediments, so what's called an ecosystem function no longer exists. The other thing is the loss of biodiversity. It's not just individual species that are lost, its whole groups of animals and that also affects the ecosystem functioning.
Interviewer - Chris Smith
Sounds pretty grim. Is there anything we can do about it?
Interviewee - Nancy Rabalais
There are a lot of things we can do. Depending on the low oxygen area and where in the world, the first thing to do is identify for the nitrogen and the phosphorus where most of the sources are. And then you can work towards reducing those sources. The area that I study the sources of nutrients is primarily from agriculture. So depending on where the sources come from and their magnitude, you need to adapt your management strategies of using less nitrogen, fertilizers, applying it at different times of the year; it's different cropping techniques; it's trying to recover what were once wet lands and putting wet lands back into a function of removing the excess nutrients from the areas; a combination of things.
Interviewer - Chris Smith
Nancy Rabalais, she is at Louisiana University where she has been looking at the problem of ocean dead zones.
(Music)
Interviewer - Chris Smith
This is the Chemistry World Podcast with me Chris Smith, still to come, a portable electronic tongue that can tell your wine's connoisseur, a new catalyst that could power the hydrogen economy and why fungi, it turns out have a taste for curry.
(14:30 - A stretchy conductor that could be made into robot skin)
Interviewer - Chris Smith
First though, there is good news for budding android builders Richard.
Interviewee - Richard Van Noorden
Exactly, well this is research by Takao Someya and his team at the University of Tokyo and what they have done is make a very, very stretchy conductive skin that could be used as a kind of electronic skin as you say, for robots to give them that wonderful humanoid appearance. What they have done here is they have mashed up carbon nanotubes in a kind of paste with an ionic liquid which is a kind of liquid where you've got ions and sort of molecules and mashing that altogether gives you, this sort of, conductive bundles of nanotubes where electrons hop from nanotube to nanotube and the ionic liquid is stopping them all clumping together. You put a silicone rubber around that and another co-polymer to get your properties just right and you end up with this sort of, rubbery sheets which is nonetheless conductive and you can punch holes in it, you can stretch it by more than a 100% and is still conductive and finally you can actually pattern transistors on top of it, to make a whole circuit. Something you could actually do, something useful like sense pressure, something like a real electronic machine and you can even stretch that by 70% and it would still work.
Interviewer - Chris Smith
Why doesn't it break the nanotubes and then make the electronics breakdown?
Interviewee - Richard Van Noorden
Well it's because there is long thin nanotubes and are, sort of, curled up and tangled with this, sort of, rubber in between them and there is enough connections, enough percolations for charge to get through. Now this is not fantastic. It's not high performance. It's not fast. We've had gold wires stuck in rubber before to create really good high performance, not particularly stretchy materials. The thing about this material is it works well enough and it is really stretchy, stretchy enough to be stretched over robot's elbow or really bendy joint and it would still work all the way across.
Interviewer - Chris Smith
So would you have to then pattern every single one of the little transistors that you wanted to do the sensing for example, see if you have got to build in a bespoke way all the skin of your android or could you just have this on a sheet or roll, you pull it off, tear it off and plaster it on.
Interviewee - Richard Van Noorden
It's a sheet. It would be done in the same way that silicon wafers are, a pattern nowadays, mass processed. First we make your conductive sheet and then you pattern the transistors on top. If you want to get some more detailed electronic architecture then you could do that automated as well
(16:50 - An electronic tongue that can tell if your Beaujolais is bogus)
Interviewer - Chris Smith
Thank you Richard, while sticking with electronic things that concerns other things this is good news for me as a wine lover, Victoria. Scientists who have come up with an electronic tongue that can tell me whether what I am drinking is the stuff I think it is.
Interviewee - Victoria Gill
Exactly. It's a tiny little sensor that acts as an electronic tongue. It's very portable and can be made quite cheaply and it can tell you the great varieties and even the different vintages of wine, it can tell the difference between difference types of wine.
Interviewer - Chris Smith
It is not as good as a human though doing that presumably.
Interviewee - Victoria Gill
No, no but this is, kind of, the key point there. Apparently, food fraud and wine fraud in particular is really big business. So if you can sell a much cheaper variety of wine that isn't grown in the, sort of, hills of Burgundy than and pass it of as the real thing then you can make quite a lot of money and fool people. So if people who are selling wine or people who are distributing it can have something to detect to sort of dip wine and see if it's the real thing and then that's going to save people a lot of money.
Interviewer - Chris Smith
And how does this work?
Interviewee - Victoria Gill
And essentially it's, sort of, a compound device that's made up of commercialized polymers. So all of these bits that have been put together to make this electronic tongue were already invented and they already exist and they can be bought. But it's a series of different polymers that have molecules embedded into them and it's the molecules that are selective for different ions and it's the ions that are responsible for the flavour of wine, sodium ions for example is responsible for salty flavour. So by putting these series of ion-selective polymers together you can sense this, sort of, the flavour fingerprints of specific wines. Because these wines are so well studied by knowing the chemistry of these wines so well, you can detect the grape varieties, you can detect the vintage, you can even detect the soil where it has been grown because.
Interviewer - Chris Smith
Well is it as accurate as that?
Interviewee - Victoria Gill
Yeah apparently, it can actually detect the same variety of wine but there is different vintages, so you can actually tell which year it has been grown.
Interviewer - Chris Smith
And is this in production yet.
Interviewee - Victoria Gill
Yeah they have made a sort of pilot scale tiny and very easy to reproduce version of it, they have actually made this electronic tongue and it's very small and very portable. So yes, this should go into production quite soon.
Interviewer - Chris Smith
But you're saying about food fraud. Surely, if you know the fingerprint chemically of the wine you want to imitate, won't this mean that then people who indulge in food fraud and wine fraud could then be tempted to try and tweak the recipe a bit to make their wine mimic better, what they are trying to make it look like.
Interviewee - Victoria Gill
It's a good point, but I guess the idea is that the fraudsters would have to, sort of, know the chemistry of their wine inside out to kind of, to get past this machine. It's a lot like drugs testing in the Olympics. You know you need to invent the tests that are sensitive enough for the next generation of drugs, so that people who want to cheat can't get past it, so you want to stay one step ahead of the fraudsters.
Interviewer - Chris Smith
So a handy gadget for picking up wine that's more border line than boudoir, thank you Victoria.
(19:38 - Richard Van Noorden explains how a new water-splitting catalyst could be the start of a solar energy revolution)
Interviewer - Chris Smith
Now as the world moves towards a more sustainable future, the race is on to find a way to produce cleaner energy. Then hydrogen is thought to be a key player. That's why a recent breakthrough in America has got scientists buzzing on both sides of the Atlantic and with the run down, here is Richard Van Noorden.
Interviewee - Richard Van Noorden
Well, to give you bit of contacts there this is research from Daniel Nocera from the Massachusetts Institute of Technology. What they are doing is splitting water up into hydrogen and oxygen gases with the hope that you then will be able to store your hydrogen and then get energy out of your hydrogen and use it in the fuel cell perhaps to drive your car or something like that. We can already split water. We can split it with electrolysis. We can use solar cells to help us in that, we can use platinum catalysts, but the problem is the platinum catalysts for example are very, very expensive. All these solar cells are very, very inefficient; you have to put in an awful lots of energy to split up H2O in to its constituent hydrogen and oxygen.
Interviewer - Chris Smith
So what have the Americans done?
Interviewee - Richard Van Noorden
What they have done is they focused on the oxygen producing end, so when you split up H2O you get hydrogen atoms and oxygen atoms, you need to recombine the oxygen atoms into O2 that has to come off and the hydrogen atoms have to come into H2, and that will actually split up into protons and electrons and that can be used to give you electricity directly or you can store the hydrogen. But they were concentrating on the oxygen evolving end which the platinum catalysts are particularly bad and what they have done is it's actually a very simple system. It's a conducting anode, a glass anode coated with indium tin oxide and you just put it in a solution of cobalt and phosphate salts in water quite cheap and a thin film starts to form on this anode and it's formed as the Co2+ ions lose electrons to the anode and they from this precipitate covering the anode up. Now this joins up with phosphates and that gives you the precipitates and after a bit of further oxidation, this film starts to pull electrons from water leaving behind protons (H+) and oxygen atoms. Now at the film surface, the oxygen atoms are brought together and they have your oxygen gas bubbling away. Meanwhile, the cobalt collects electrons and falls back into the solution ready to be regenerated by oxidation, returns to the film surface again and your protons are carried away by the phosphates in the solution to a conventional platinum electrode where they gain electrons to form hydrogen. So it's a bit complicated there, but basically it's a cobalt and phosphate very simple system for producing oxygen and splitting up water.
Interviewer - Chris Smith
And it's doing it for less energy inputs than you would normally need presumably to do that.
Interviewee - Richard Van Noorden
Yeah, what seems to be very clever about this, really the platinum is a bit of over kill, you're really putting too much energy and that splits up the water and it's the same with the solar cells where you're just splitting the water by electrolysis. This seems to be just right, just the exact amount of energy needed and it seems to be catalytic. So what Nocera says is that you could have a solar cell making electricity directly from the sun shining on it but what if you could not use that electricity straight away; that the demand wasn't there. You might want to store up your energy; all you would do is you would use your electricity to get these electrodes going, start splitting up water and form a storable hydrogen fuel that you can carry around in tanks.
Interviewer - Chris Smith
Why is that better than a battery?
Interviewee - Richard Van Noorden
Because hydrogen is a much more compact form of energy storage than a battery so far. So that's why people are really gunning for it. That's why people are even suggesting that it be used in cars, because batteries would just be too heavy, you need too much of them in a car, to make a car run for the distances we're accustomed to and the hope is that hydrogen can meet that problem and if you could pressurize hydrogen into a liquid then you could start to have infrastructure like big tankers that could carry the hydrogen around and the idea is that you would have something approximating to our current liquid fuels idea. Now Nocera is calling this artificial photosynthesis and the reason he says is that a leaf which does photosynthesis splits up water and combines the protons with carbon dioxide, clean from the air and stores that up in much longer molecules like starch and glucose and then it will break them down to get the energy. We kind of doing the same thing here; we are splitting up water here this catalyst is getting with the oxygen side of that but then we are taking the protons and electrons and if we are not using electricity directly we are storing it up, we are storing it up as hydrogen which we are then going to break down, but the idea is that it is an ar
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