Chemistry World Podcast - September 2011

1:05 -Tequila for your fuel tank

3:02-Possible origin of chirality in the RNA world

6:47-Neil Fox explains why diamond is a chemist's best friend for generating electrical power from sunlight because of its unique properties

12:57-Spotlight on polymerisation to repair damaged faces

16:15-Nanorobots powered from beneath the skin

18:28-Alan Clarke wonders whether we've been looking at cancer therapy the wrong way - should we be looking for more powerful cancer stem cells?

25:35-Magnetic sponge can squeeze itself out

29:07-Cyclodextrin dimer becomes synthetic polymerase

32:14-Trivia - Why might you put mushrooms on a tanning bed?

(Promo)

Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.

(End Promo)

Interviewer - Chris Smith

Hello, this is the September 2011 edition of the Chemistry World podcast. I'm Chris Smith and with me this month are Josh Howgego, Laura Howes and Elinor Richards. And we're discussing the link between biofuels and tequila. Yes, trust me there is one while mushrooms benefit from a blast of UV and also how diamonds could hold the key to the most efficient photovoltaic devices ever made.

Interviewee-  Neil Fox

So, it takes in any form of sunlight or it could be any form of heat, in fact the light hits the receiving surface with the diamond coating and the diamond converts the lights into electrons.

Interviewer - Chris Smith

And you can hear Neil Fox explaining how his new diamond based device works, very shortly.

(Promo)

The Chemistry World Podcast is brought to you by the Royal Society of Chemistry. Look us up online at chemistryworld dot org.

(End Promo)

(1:05 - Tequila for your fuel tank)

Interviewer - Chris Smith

And to kick us off, margarita lovers listen up. Elinor.

Interviewee - Elinor Richards 

David King from the Low Carbon Mobility Centre at the University of Oxford and his team, have shown that the Algarve plant can be used as a bioethanol feedstock instead of corn and sugarcane. So the problem with getting bioethanol from corn and sugarcane is that they're obviously food sources too. So there are concerns about land to grow the sources, so the question is should the land be used for fuel or food?.

Interviewer - Chris Smith 

So, why is Algarve better than using traditional, what we call traditional sources of bioethanol.

Interviewee - Elinor Richards

Algarvecan grow in arid areas, so the plants don't need water and they don't intensive fertilizer that the sugarcane and corn need.

Interviewer - Chris Smith

Okay, so they're good, potentially brewing into their use. Areas of land, which at the moment are lying fallow, there's not much to use them for because nothing grows there, you could plant this stuff on there. What sort of contribution to the biofuel effort could it make?

Interviewee - Elinor Richards

Well, there's no shortage of desert land and there are also deprived areas located on the edges of deserts, so this could be a method to utilize that unused land and help rejuvenate these deprived areas.

Interviewer - Chris Smith 

Is he very good as a source of material to turn into bioethanol, this particular plant?

Interviewee - Elinor Richards

Yes, but there are a few problems I know before it can be used as a feedstock. They are slow growing crops and until they have been harvested manually, so you have labour issue and the yield issue, but the researchers do say that they can work on increasing yield and ultimating the harvesting.

Interviewer - Chris Smith

It would be nice. Now there's one very important thing you haven't touched on yet, which is that apart from being feedstock for bioethanol, tequila is an important human feedstock for various things including margarita, so that's also made from the same plant, so is that likely to be an impact on this or not?

Interviewee - Elinor Richards

Well, the researchers do assure us that actually the tequila supply will be fine.

(3:02- Possible origin of chirality in the RNA world)

Interviewer - Chris Smith

Well that's bit of an insurance, but I'm surprised we even bothered to mention it, but there we're, thought I'd catch you with that, now Laura Howes, we've discussed this sort of concept before in the Chemistry World podcast, which is the whole question of where life came from and how life got started and there's this whole idea of the RNA world hypothesis, actually where the nucleic acids just popped up to start with and then began to become self replicating and ultimately became cells or so on. But one of the big outstanding questions is why they have a particular handedness, this chirality question, molecules coming right and left handed flavours and why life, almost universally uses left handed amino acids to make proteins and right handed sugars and things like its DNA.

Interviewee - Laura Howes

That's right Chris. However, much you might want to support the RNA world hypothesis and show that you can take these simple precursors and make the beginnings of RNA. Up until now, people have only been able to make what we call racemic precursors, so an equal mix of these left and right handed molecules and that's not what we have in our bodies, that's not what life is today.

Interviewer - Chris Smith

Indeed, so what do they think could have accounted for the fact we have this stark contrast, this particular type of molecule is exclusively used in life versus the other isomers.

Interviewee - Laura Howes

No one will ever really know. We're not going to be able to go back in a time machine, but people are trying to play with this idea and Donna Blackmond at Scripps in the US was noticing that if you have one particular handedness molecule that can often direct how a reaction will go, but that doesn't help matters because if you've got a hundred percent right handed molecule that just sends the question back to how did you get hundred percent of this right handed or left handed molecule.

Interviewer - Chris Smith

Indeed. So what is she saying could have tripped life or whatever to adopt to one particular handedness of flavour of vanilla.

Interviewee - Laura Howes

What's she's actually shown is that you actually need a very, very slight mismatch so you could have say 49% of one handedness, 51% of another and that will be enough to knock everything and then what is going is gone and it all spirals well, but it amplifies from that.

Interviewer - Chris Smith 

So what experiment did she do to prove that then?

Interviewee - Laura Howes

Well there is a quite simple experiment, quite simple reaction that people have done to create RNA precursors, just using a three-component reaction using glyceraldehyde and 2-amino-oxazole and then one of the , while you can use any amino acid that tends to be what you used to direct the chirality. Donna had seen that if you use Proline, that's a very good one for directing how the reaction will go and she proved this with a 100% one handedness of protein and suddenly enough it all went in one direction and then she mixed them up together, a racemic mix of a left handed right handed mix of one left handed right handed mix with another and then with the Proline, with a very, very slight imbalance and still it managed to go all the way to being the Deoxyribonucleic acid which is the one that we have today.

Interviewer - Chris Smith

Does she give any suggestions as to why because one suggest is that life adopted a particular bias because there was a predominance of that particular form of molecule handedness back in the early vestiges of the earth.

Interviewee - Laura Howes

Yeah.

Interviewer - Chris Smith

And one suggestion is that the reason that there was that predominance is because things like meteorites and comets raining in from outer space just by chance happen to have a bias towards one particular isomer.

Interviewee - Laura Howes

Sure, we don't know what it is if the RNA will hypothesize indeed is the one that actually worked and that's one possibility. The other possibility is just that when you take a reaction, you will get these little imbalances, it's like flipping a coin, you might get ten hits in a row any one time, and that could be just like that. 

(6:47- Neil Fox explains why diamond is a chemist's best friend for generating electrical power from sunlight because of its unique properties)

Interviewer - Chris Smith

Just like that, as Tommy Cooper would say. Thank you Laura. A major priority worldwide is to make much better use of the terajoules of energy that hit the earth in the form of sunlight everyday. Bristol scientists, Neil Fox is working on a way to do that with diamonds by producing a thermionic energy converter that can capture light energy including infra red and pump out power.

Interviewee - Neil Fox

The aim of the project is to produce a demonstration of a technology called the thermionic energy converter to develop a new material, a nanostructured material based on diamonds. The attraction of diamonds is that it's incredibly resistant to corrosion. It can be cycled many times and in a solar application, where there are constant heating up and cooling down cycles occurring each time the sun goes in and out, this is particularly important, but we're interested in the surface of diamond because it's at the surface of these diamond materials that we have energy conversion taking place.

Interviewer - Chris Smith

James Bond famously used diamonds in Diamonds Are Forever or at least the bad guys did. They wanted to make a laser, but you're talking about actually using the diamonds to capture solar energy.

Interviewee - Neil Fox

That's right. Its not really a solar cell, let's say, it's a solar energy converter that so it takes in heat or thermal energy that could be any form of sunlight or it could be any form of heat, in fact, but if we concentrate on solar, then it's a broadband absorber effectively which means that all the light hits the receiving surface with the diamond coating and the diamond converts the light into electrons and they're given off past across the device and on the other side of this device, they're captured, give up a lot of heat, but they also carry potential energy in addition to that kinetic energy, which is the heat, and if that potential energy is then used to generate a voltage across the device and because we've already moved those carriers across from one side to the other from the hot side to the cold side, that means that so we're able to generate a electrical power output from this device.

Interviewer - Chris Smith

So, can we look for a second at actually what is happening at the surface when the photons, the light particles come in and impact on the diamond surface? How are they doing the energy transfer? What actually is happening chemically in the diamond to do that?

Interviewee - Neil Fox

So electro optic effects really, the heat promoting carriers to a high level where they can be moved out of the material into a vacuum. That's essentially how a thermionic emission works. You're giving carriers in the material, kinetic and potential energy and that lifts them over the energy barrier and allows them to escape and move away from the surface. 

Interviewer - Chris Smith

So why does diamond have lots of carries that are available to be knocked out like this and made available.

Interviewee - Neil Fox

Diamonds although it seemed to be an insulator is essentially a semiconductor with a very wide band gap and it's possible to introduce impurities into this synthetic material that we use to make it easier to promote electron carriers into what's called a conduction band and in this case, the carriers are being moved towards the surface. And once at the surface what they see in diamond is a launch pad because the diamond surface has been functionalized, so we put chemicals on the surface to change the effective ease with which you can get them off the surface. Otherwise, we change the work function of the surface and the way we've done that is to functionalize this surface with lithium and oxygen and what that does is it's easier for those carriers to escape back into vacuum.

Interviewer - Chris Smith

So that coating grabs the carriers as they're generated by the diamond, you can then tap them off.

Interviewee - Neil Fox

That's right. They're pulled out of the surface, if you like. 

Interviewer - Chris Smith

So, if you get this working how much energy will you get?

Interviewee - Neil Fox

Well, typically in the UK, you're looking at during the summer times, certainly about two and half kilowatts per square meter and we would be looking to convert about 25% of that into electrical power if not more and that's quite high compared to typical silicon solar cells, they're about 16 to 18%. The reason why Thermionics are so much high is because it can operate by using a much broader range of the spectrum, so from that point of view conversion rates ought to be higher. Also this device for the application for utility scale, we've got to pitch it to quite a high level because the utility concentrated solar insulations what they have in places like southern Spain, typically the system efficiencies there are about 22%. So for thermionic energy converters to work at a utility scale, we're really got to get up to efficiencies which exceed that, so that they do have some benefit for that type of installation. The other application we're particularly interested in this is micro generation; being able to put this technology onto housing, onto factories, super markets alongside conventional solar panels and the benefit there is that power density is a lot higher because we use concentration. So concentrate the radiation onto these devices and it also produces waste heat in the form of hot water. So it's very much a solar thermal technology but with the added benefit of diffusing both electricity and waste water.

(12:57- Spotlight on polymerisation to repair damaged faces)

Interviewer - Chris Smith

Neil Fox and he reckons conservatively that they're just three years away from a commercial product, hitting the markets. Aren't diamonds, wonderful things. Now Josh apparently there's every reason to turn the other cheek with a new skin repair material.

Interviewee - Josh Howgego

Yeah, so basically there's a bit of a problem where if you have damage to soft tissue, the sort of thing that's in your cheeks that kind of thing, sometimes it can be quite difficult for that to be repaired because basically we need some kind of support to help the tissue grow back and there's kind of two approaches you can use, you can use like a synthetic artificial material, but often there's problems with that kind of thing because it can kind of be rejected by the body, but it can cause severe inflammation and those kind of undesirable side effects or the other option would be having a graft of soft tissue from somewhere else but that's got the issue of well one you've got to find somewhere to take it from, which might not be that fun and also the fact that that can de degraded very quickly sometimes by the body as well. So neither of those two things are perfect solutions.

Interviewer - Chris Smith

So, what have you got to offer instead?

Interviewee - Josh Howgego

(Laughs)So, we have instead is a piece of work which is being carried out by Jennifer Elisseeff from Johns Hopkins University in the US and what she's done is basically created a pretty simple system. It's based on polyethylene glycol which is a polymer, which is known to be biocompatible, so it doesn't get rejected by the body and she's used this, which has got some methacrylate side chains on it and she's added in another biocompatible kind of crosslinker plus a photo initiator molecule. What she can do is inject a mixture of those components into a region which has been damaged for example in a face or something. That mixture can then be massaged to give the correct sort of structure and then you can irradiate it with an ultraviolet light and then the crosslinking will occur.

Interviewer - Chris Smith

And it polymerizes fixes.

Interviewee - Josh Howgego

Exactly, yeah it crosslinks. 

Interviewer - Chris Smith

How neat, so you can actually put the skin or the tissue into the configuration you want and then almost fix it with the UV light, does the UV get fine off in to do a good job of that?

Interviewee - Josh Howgego

They've had to modify a little bit I think because you do have to foresee some problems with penetration with the UV sometimes and also bit worried that you get like, you know, sunburn or something, that they've tested it on rats and apparently there's no problems.

Interviewer - Chris Smith

I guess it will also depend on the wavelength of the UV because longer wavelength UV is probably bit safer, but that would depend on what the molecules are and where they absorb the energy.

Interviewee - Josh Howgego

That's right

Interviewer - Chris Smith

The problem I can see with those, how did you get the polyethylene glycol scaffold back out again, once it's done the job and helped the tissue to fix

Interviewee - Josh Howgego

Well yeah, obviously we want to be able to do that and how the guys do is that they inject some enzymes, which are able to digest the carbon oxygen bonds and then it will just degrade and obviously creates biocompatible products I guess.

Interviewer - Chris Smith

When it is in there, what's its role, how is it helping tissue to get better?

Interviewee - Josh Howgego

Well, it's not really doing anything on kind of biological level, basically just add acting as a scaffold so that filaments and tissue can just basically use it as a scaffold to grab on basically.

Interviewer - Chris Smith

So, it guides cells back into where they need to go to make a wound heal

Interviewee - Josh Howgego

Yeah it does. 

Interviewer - Chris Smith

And just in rats or have they actually got some clinical data from people now?

Interviewee - Josh Howgego

We spoke to the researchers and they said that at the moment, it's only in rats but they're working to do some human trials at the moment.

(16:15- Nanorobots powered from beneath the skin)

Interviewer - Chris Smith

Thanks Josh. Well let's stick with the skin and Elinor you're going under the skin in a different way and this is a way of powering up nanorobots.

Interviewee - Elinor Richards

Oh yes! Science fiction comes to life. So there's a team from the National Chiao Tung University in Taiwan, led by Fang-Chung Chen. What they've done is they've made a small power device that can be inserted underneath your skin and these can control nanorobots, sort of placed in your body for medical purposes.

Interviewer - Chris Smith

Gosh! So how does this work, this thing that you implanted, makes electricity?

Interviewee - Elinor Richards

It does. Yeah, it takes energy from infrared light. It converts the light energy within it to an electrical output that can control the nanorobots

Interviewer - Chris Smith

What would you view the nanorobots is doing? How do they say this could be used?

Interviewee - Elinor Richards

Well, the researchers suggest that could be used to inhibit pain or control a disease, for example.

Interviewer - Chris Smith

Because that would be more futuristic, so focussing on here and now with the actual power patch, chemical speaking how does it actually work?

Interviewee - Elinor Richards

Well, it's a two-layer organic photovoltaic cell. The layers are sandwiched between conducting layers and obviously in two layers, one layer is an electron donor and the other ones is an electron acceptor and when a light photon is absorbed by the acceptor and that comes from the infrared light that's been shown on the device, this creates an electron-hole pair on the interphase between the donor and the acceptor and then the pair disassociates at the interphase and this creates the current.

Interviewer - Chris Smith

And how much energy can this thing make? What's the energy density?

Interviewee - Elinor Richards

Well, when the team measured the electrical output, it came to 0.32 microwatts and they say that it is more than enough to drive many biological nanodevices at the same time.

Interviewer - Chris Smith

So, what's the energy demand of a nanorobot then?

Interviewee - Elinor Richards

So, the typical power needed for one nanodevice is approximately 10 nanowatts. 

Interviewer - Chris Smith

So, should be more than enough for a whole army of nanorobots

Interviewee - Elinor Richards

Should be yes, yeah.

Interviewer - Chris Smith

Okay. Thanks Elinor.

Interviewer - Chris Smith

You're listening to the Chemistry World podcast in September 2011 with me Chris Smith. Still to come, the nanosponge that you can wring out magnetically. First though to Kansas and how scientists have come around to the idea that lurking inside a tumour are some cells that are far more malignant than others because they behave as stem cells capable of receding a tumour even after surgery or chemotherapy has wiped out the bulk of the disease. 

(18:28- Alan Clarke wonders whether we've been looking at cancer therapy the wrong way - should we be looking for more powerful cancer stem cells?)

Interviewee - Alan Clarke

My name is Alan Clarke and I'm a Professor of Cancer Biology at Cardiff University and one of the things that my laboratory works on is understanding the link between those cells which are stem cells in your normal body which do things like repair your normal tissues and the link that those cells that might have with tumours, which are often considered to be unregulated growth of stem cell equivalents, which drive tumour development.

Interviewer - Chris Smith

So, the bottom line is that where we've gone from a perspective of a cancer was the big growth of cells, They're all mixture of mixed bag of cells, but if we chop that tumour then all be well, we now have a mindset that underlying that could well be cells that have the ability to regenerate or rekindle that tumour, if we leave any of them behind.

Interviewee -- Alan Clarke

Its already known for a long time that cancers are heterogeneous and that means that not all of the cells are equivalent within the cancer and for sometime we've known there's been a subpopulation of cells which are particularly good at reforming the tumour if you separate the cells out and that's been what their capacity is to rebuild the tumour and some seem to be much better doing that than the rest of the tumour. And so you actually say this has given notion to the rise, given rise to the notion that there are population of driving cells within a tumour and it's actually a small population of cells which caused the tumour to originally grow and then when you treat it with conventional therapy when that tumour can relapse and re-grow again it forces off actually drives out.

Interviewer - Chris Smith

What about when we look at treatment for cancers though because many treatments focus on tumour bulk reduction? You give a chemotherapy agent and it destroys millions of cells, but are these stem cells equivalently vulnerable or not?

Interviewee - Alan Clarke

This has again where it potentially becomes exciting is that perhaps we've been looking at tumour therapy in the wrong way. Traditionally, we would look at therapy as being successful if it de-bulks, if it reduces the size of the tumour. If you kill cells within a tumour, the end result normally is the tumour gets smaller. However, if what you're doing is killing the cells which are in the drivers within the tumour, you're actually killing the non-driving cells and the tumour apparently responds but in fact the cells which are the driving cells are left intact within the tumour and the tumour can fully grow back again. What you've done is fail in your therapeutic approach in fact and what you might need to do is go in and look for therapies which specifically target the driving cells.

Interviewer - Chris Smith

How can we spot those needles in the haystack because these stem cells are presumably there only at much lower frequency compared with the vast bulk of the tumour?

Interviewee - Alan Clarke

It is this concept, the notion that actually those driving cells within the tumour share a lot of properties with normal stem cells and that's why they've been called a cancer stem cell. And we think that actually by looking at the normal properties of normal stem cells in normal tissues, we're going to get clues which will allow us to identify the cancer stem cells so called sits within the tumour and acts as the driving population and it would be a comparison on the contrast and a comparison between those two populations, the normal stem cells and the cells which might drive the tumour, which we think will allow us to find that needle in the haystack and go in therapeutically kill it, the driving cell within the cancer.

Interviewer - Chris Smith

This seems to be a day for clich?s, from needles in haystack to chickens in eggs. Do those stem cells come first and turn into tumour cells or can some of the tumour cells actually go back and turn back into stem cells.

Interviewee - Alan Clarke

Yeah, so this and again this is one of these terribly important questions and needs to be answered now is where, I think, we're more interested at the moment is in this transit from the normal stem cell to a potential cancer stem cell as a driver within the tumour and we think we've got fairly good evidence if that process happens with a reasonable efficiency first, understanding the switch is that that turn a normal stem cell into one that can drive the tumour, which I think is perhaps an area of, which is going to be very fruitful. 

Interviewer - Chris Smith

Now one of big problems with treating cancer that we've seen all along is how to get the treatment selective, so they pick on just the cancer and they leave the healthy tissue and it's when that doesn't happen, you get terrible side effects. If we're going to end up with therapies that target stem cells, are we going to see even more of a problem trying to make it selective for the cancer stem cell?

Interviewee - Alan Clarke

Well, again yes and again it's down to understanding the differences in the switches that turn a normal stem cell into a cancer stem cell which allow us to generate therapeutics which specifically target the cancer stem cell and not the normal stem cell. We do have something going for us in that we know that there is large plasticity and great capacity for repair within the normal tissue so that even if you do delete the normal stem cell, you can repair that what we call as niches where the stem cell will reside and there is sufficient plasticity within the system that you can rebuild the stem cell population. So you can produce therapists which actually we will do this in an experimental setting where you actually wipe out all of the cells, all of the normal stem cells and indeed all of the cancer stem cells but there's still sufficient plasticity within the normal tissue that you can rebuild the normal stem cell population.

Interviewer - Chris Smith

And if I could hand you a very large cheque from one of these research councils that used to have a lots of money to give away and now has less, what would you spend it on in this field, where do we need to direct our funding in the next five years.