Chemistry World podcast - February 2012
1.07 - Determining the age of bloodstains using fluorescence
3.51 - Magnetic nanoparticles to remove cadmium from blood
6.07 - Paul Bertsch discusses using worms to investigate the effects of silver nanoparticles in the environment
12.12 - Controlling termite populations with nanoparticle technology
15.04 - Listening to the sounds of a cell with the nanoear
19.05 - Scott Mabury looks at the issues surrounding fluorinated chemicals making their way into the food chain
26.20 - Metal hip replacements provide their own lubrication - graphite
29.33 - Did the TNA world come before the RNA world?
32.53 - Trivia: Chinese inventions
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
Interviewer - Chris Smith
Hello. This month, magnetic nanoparticles to trap toxins in bloodstream. How scientists are listening to individual proteins inside cells now and hip replacements that make their own graphite lubricants. Plus what happens to silver nanoparticles once they get into the environment.
Interviewee- Paul Bertsch
What happens in this assay is the earthworms can actually choose which soil they go into. In the case of the nanosilver, they didn't avoid the soils at first, but rather after being exposed for sometime in the soil they actually left the soil and to the controlled soil.
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Interviewer - Chris Smith
That's Paul Bertsch, who will be talking to us later in the program. And also with us are our Chemistry World regulars, Bibiana Campos-Seijo, Phil Robinson and Elinor Richards. And I'm Chris Smith.
(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)
(1:07 - Determining the age of bloodstains using fluorescence)
Interviewer - Chris Smith
And up first up how chemists are turning detective, Bibi.
Interviewee - Bibiana Campos-Seijo
Okay. So, determining the age of a blood stain at a crime scene is one of the greatest challenges in forensic science. And this team of researchers led by Mikhail Berezin at Washington University in St. Louis have come up with a method that seems to work. It allows them to determine the age of the blood stain and is particularly accurate within the first seven days of the blood stain being made.
Interviewer - Chris Smith
You mentioned that it's critical in forensics to do this. With present techniques that pre-date this one, how do they do it then?
Interviewee - Bibiana Campos-Seijo
They use optical measurements of haemoglobin degradation, which seems to be quite unreliable. So, this new method seems to be fast, reproducible, concentration independent and requires a very, very small amount of blood to actually carry out the measurements.
Interviewer - Chris Smith
Sounds like good news. You better tell us how it works then.
Interviewee - Bibiana Campos-Seijo
Well, this group of researchers have developed a technique that relies on the fluorescence lifetime of tryptophan. They have been able to measure this because a new laser became available that was specifically designed to look at tryptophan and actually it uses a wavelength of 295 nanometres.
Interviewer - Chris Smith
So blue laser light.
Interviewee - Bibiana Campos-Seijo
Yes. So, tryptohan's fluorescence is not very sensitive to its environment. So, what happens is that the proteins, with the changes in the environment, the proteins age and degrade and the fluorescence lifetime decreases, so they were able to measure that.
Interviewer - Chris Smith
How did they standardize this because different environments might make the tryptophan break down more quickly, also how do you know roughly how much tryptophan is there because there'll be different amounts of the amino acid in different blood samples. So how did they get a standard for it?
Interviewee - Bibiana Campos-Seijo
Well at the moment, they only have done this in the lab. They've used blood from dogs, and they' then carried out the degradation in Petri dishes. So, they haven't seen what happens when there are organic surfaces or what happens in the presence of bacteria or anything like that. So, to an extent that is research that still needs to be carried out. In terms of the standard, we know that the method is concentration independent and basically because they measure the lifetime, they're not looking at the actual concentrations.
Interviewer - Chris Smith
So, they're looking at the lifetime of the fluorescent signals rather than its amplitude, which will be proportional to the amount?
Interviewee - Bibiana Campos-Seijo
To the concentration, yes, yeah.
Interviewer - Chris Smith
So that sort of irons out that problem.
Interviewee - Bibiana Campos-Seijo
Yes, yeah.
(3:51 - Magnetic nanoparticles to remove cadmium from blood)
Interviewer - Chris Smith
Genius stuff. Well let's stick with the blood. And Elinor tell us about a way of getting things out of the blood that shouldn't be there, in this case, we're talking cadmium
Interviewee - Elinor Richards
Yeah. Yes. Heavy metal pollution is on the rise. According to researcher, Jun Jin and Jiantai Ma from Lanzhou University in China and they've developed a nanoparticle to inject into the bloodstream to pick up one of those heavy metals, cadmium so that it can be removed just by using a magnet
Interviewer - Chris Smith
Seems ironic to inject one toxic thing potentially to get another one out. What's the particle they put in?
Interviewee - Elinor Richards
It's a nanocomposite and it's made up of four components. So, the first one is magnetic iron oxide nanoparticles and they've been chosen because of their low toxicity and then they coated these with a polymer, polyethylenimine which binds to cadmium. This has another function as well, it also reduces the chances of nanoparticle uptake by red blood cells. So it maximizes their circulation time in the blood and then they grafted polyethylene glycol into this as an anchor for negatively charged 2,2'-(phenylazanediyl) diacetic acid.
Interviewer - Chris Smith
Easy for you to say. What does that do?
Interviewee - Elinor Richards
And this counteracts interactions between the nanoparticles and the plasma proteins or white blood cells.
Interviewer - Chris Smith
Or stopping them getting anchored onto the wrong things?
Interviewee - Elinor Richards
Yes, wrong things yes.
Interviewer - Chris Smith
Okay. So that gets the particles whizzing around the circulation and collating lots of cadmium. How to get them out again?
Interviewee - Elinor Richards
With a magnet.
Interviewer - Chris Smith
Doesn't sound too trivial though because these things ruin your bloodstream. You don't take someone to scrap yard and put them under the dangly magnet, presumably.
Interviewee - Elinor Richards
No. Jin thinks that the nanocomposites would be injected into a vein to start with and they would bind the cadmium-iron and blood and then be removed by circulating the blood through a magnetic field, attracting the nanocomposite, cadmium-iron complexes and then the detoxified blood would then be returned to the body.
Interviewer - Chris Smith
So it's a bit like when you do kidney dialysis, you could have this as an extra bit of plumbing.
Interviewee - Elinor Richards
Yes.
Interviewer - Chris Smith
How practical is this? And how much of a problem is cadmium or other heavy metal poisoning that would really make this worthwhile.
Interviewee - Elinor Richards
Well, the toxic metal ions they bind to proteins in the body and they affect the proteins' function and this can eventually lead to organ damage or possibly cancer.
Interviewer - Chris Smith
Definitely a case of prevention being better than cure, by the sound of it. Thanks Elinor. And talking of nanoparticles.
(6:07 - Paul Bertsch discusses using worms to investigate the effects of silver nanoparticles in the environment)
Interviewee- Paul Bertsch
My name is Paul Bertsch. I work in the area of environmental chemistry and toxicology; I'm a professor at the University of Kentucky. Over the past decade there has been an explosion in the manufacturing as well as use of nanotechnology in many products that are used regularly and one of the emerging issues is what are the potential environmental implications of nanomaterials, being released from these products into the environment? Are they taken out by organisms in the environment, and can they be transferred through food chain with potential exposure to humans as well?
Interviewer - Chris Smith
This is a question of we've learned our lesson from things like asbestos. We don't want to repeat.
Interviewee- Paul Bertsch
Yeah that's correct. Asbestos or you may even think of pesticides, like DDT or even mercury that's anthropogenically released, typically from coal fire plants.
Interviewer - Chris Smith
I mean, this sort of idea about nano-hazardicity has been knocking around for a little while though hasn't it?, at least five years, people have been saying there is this risk but what are people actually doing about it, and what is the objective evidence that there might actually really be a problem.
Interviewee- Paul Bertsch
The picture is still not totally clear yet. What we're trying to do as a community of scientists coming at this from very different angles is to again understand what properties of the nanomaterials as manufactured, as well as what properties has transformed once they're released to the environment or taken up by a biological organism or critical relative to toxic effects to those organisms.
Interviewer - Chris Smith
So, tell us about your worms then.
Interviewee- Paul Bertsch
So, our earthworm studies have been conducted, actually in soil. So the nanomaterials are added to soil and are the earthworms are allowed to be raised in that soil for 28 days and we look at accumulation of nanomaterials in the tissues as well as any effects based on things like lethality, so toxicity in terms of lethality, reproduction and also behaviour and what we found was that the silver nanomaterials for example were far less toxic than dissolved silver, orders of magnitude less toxic in terms of lethality and reproduction. What we also discovered however, that was quite a surprise is in terms of behaviour and this is measured by the earthworm's ability to avoid soils containing nanomaterials, the earthworms were sensing these nanomaterials at quite low concentration levels and levels that could not be explained by the release of dissolved silver.
Interviewer - Chris Smith
How do you know they were sensing them?
Interviewee- Paul Bertsch
So, it is known that earthworms for example will avoid soil with low pH and having metal contamination and even some organic contaminants and so what happens in this assay is the earthworms can actually choose which soils they go into and a hundred percent of the case is soil contaminated with dissolved silver that is silver ion, they avoid it in all instances and then in the case of the nanosilver, at first they didn't avoid the soils at first but rather after being exposed for sometime in the soil they actually left the soil and went to the controlled soil and so we assume that what's happening there is that they're sensing either the particles or the particles are interacting with their cuticle and releasing dissolved ions for example that they then sense.
Interviewer - Chris Smith
Now how long do you think these things might hang around for because if you look at the DDT story or even the asbestos on my garage roof, the evidence is these things hang around for a very long time in the environment; so do we think that things like nanoparticles of silver are going to have a similar longevity effect?
Interviewee- Paul Bertsch
Well, in the case of silver, it's little bit more complicated because they transform chemically, a sulphide and the transformation of silver metal nanomaterials to silver sulphide nanomaterials is actually quite rapid under a wide range of environmental conditions. Certainly in waste water treatment process, this appears to be a very important reaction that occurs rapidly and the silver sulphide particles then appear to be stable and because of the very low solubility of the silver sulphide phases, it could be that they would remain stable for very long periods of time, but one of the complexities in this whole area is that manufactured materials are manufactured in many different ways, so not only is size an issue, as we get under the nanoscale, we have things, other different properties of these nanomaterials to shape the actual crystalline form as well as what types of surface functional groups are put on during the interaction. So depending on what the coding is, the nature of the coding and how that coding interacts once that particle is put into an environmental matrix, you know, all these factors are very complicating in terms of trying to be able to predict what will happen in terms of longer term reactivity. These particles presumably could be stable for quite some time.
Interviewer - Chris Smith
What should we be doing to make sure that we mitigate this risk or at least are in a position to identify what the threats are to control them before we just massively upscale the production of these things because we can see lots of tangible benefits to industry and society and so on and then might actually be a lot of dirt being swept under the carpet with this.
Interviewee- Paul Bertsch
The benefits of nanotechnology are clear and I think where we really need to take the research effort is take the collective evidence that is been generated thus far and begin to piece together a picture of what properties of nanomaterials actually make them less bio-available, less toxic and less benign and kind of think about a research effort that's focussing on a safe design of nanomaterials.
Interviewer - Chris Smith
Paul Bertsch from the University of Kentucky and now to some things slightly larger than a nanoparticle, but with huge potential to be destructive, Elinor tell us more.
(12:12 - Controlling termite populations with nanoparticle technology)
Interviewee - Elinor Richards
Termites are a big problem in Australia and they cause an estimated two billion dollars of damage to buildings. So, Australian researchers led by Zhang Qiao at the University of Queensland are looking at more effective ways of killing them than what's currently on the market.
Interviewer - Chris Smith
I now remember being gob smacked when I went to see a friend of mine in Perth and I couldn't understand why they had metal fence because this seemed like an extraordinarily expensive way to enclose your garden and they said because the half life of a wooden fence in this part of Australia would be measured in milliseconds because the termites would just come along and eat it and so I can understand this kind of a problem. So, what are they doing instead then?
Interviewee - Elinor Richards
The conventional solution is to use agrichemical biocides like DDTs, dichlorodiphenyltrichloroethane and they've been using wooden sticks and surrounding a property and putting the biocide onto the sticks and the termites come along chomping away everything that's wooden.
Interviewer - Chris Smith
So, it's actually like these are stakes as in wooden bait for termites, with termite food being impregnated with nasty things.
Interviewee - Elinor Richards
Yeah. They would come along and they would chomp on these and then die, but the problem with that is you're only killing a handful. What you need is.
Interviewer - Chris Smith
And there's also an environmental impact that you got the chemicals that are on there, leaching out of everywhere.
Interviewee - Elinor Richards
Exactly, I mean they could bio-accumulate which means they go up the food chain and cause lots of effects.
Interviewer - Chris Smith
And because you're not targeting it just at the termites, the dose you have to put into those louvres would probably be quite high.
Interviewee - Elinor Richards
I would imagine so, yeah. So, what they've done instead is they're putting the biocides directly into the colonies, by putting them inside silica nanoparticles with lots of tiny pores and the particles release the biocide in a controlled manner. So, it takes about 48 hours at the moment for this biocide to leak out and this means that the termites that get onto the biocide, they get affected by that but then they move further into the colony and spread the biocide around killing a lot more.
Interviewer - Chris Smith
What, sort of, trials have they done to prove this can work?
Interviewee - Elinor Richards
They have done a small trial, a small test on a group of termites and it did work. They monitored over 48 hours and in 24 hours it did kill all of them, the termites. This isn't ideal because it was killing too quickly, they want the slow-release mechanism to spread through the entire colony.
Interviewer - Chris Smith
The stuff that they're using is there an environmental risk with this or is it better?
Interviewee - Elinor Richards
This is better because it goes directly into the colony. So it's less likely to be picked up perhaps by predators.
(15:04 - Listening to the sounds of a cell with the nanoear)
Interviewer - Chris Smith
Well let's get really small now. Phil tell us about the nanoear, I'm intrigued to hear about this one, what's going on.
Interviewee - Philip Robinson
Yeah, the nanoear Chris. You and I know that in our macro scale world that we live in it's filled with the science of machinery and very often the science of these machines will tell us something about the operation of those machines, I certainly know my bike chain at the moment probably needs a bit of looking at.
Interviewer - Chris Smith
Engine of my car.
Interviewee - Philip Robinson
Well precisely precisely. Similar to that, at the micro-scale, we also have machinery. We have proteins in cells and a lot of chemists spend a lot of time building that molecular machines as well. So, just as the machines on our macro scale world, well that will make noises, so do these micro scale machines, produce acoustic vibrations but of course, we can't listen to those.
Interviewer - Chris Smith
Because they're too small.
Interviewee - Philip Robinson
Because they are too small. Yes exactly, exactly. The energy of these vibrations is far too tiny for us to be able to listen to our ears simply are not sensitive enough.
Interviewer - Chris Smith
So how could we pick them up?
Interviewee - Philip Robinson
Well that's the problem that Jochen Feldmann has taken a look at. He works at the Ludwig Maximilian University in Munich and along with his team, they had an idea that they could use optical tweezers to do this. So optical tweezers are a means of confining very small objects using a laser beam. What Jochen proposed was that by looking at the motion of a particle that's trapped in optical tweezers we should be able to tell something about the environment that it's in.
Interviewer - Chris Smith
Because it will pick up the vibrations from that environment.
Interviewee - Philip Robinson
Exactly, exactly. In fact, he puts it very nicely himself. He likens it to an apple hanging on a tree branch. If the apple is being moved by the wind, by looking at how the apple responds to the wind, well that will tell you something about the wind itself.
Interviewer - Chris Smith
But what about the fact that it might be hanging on a very big stiff thick branch, that doesn't move very much or it might be hanging on a twig therefore move in a different way. How can you discern those two, because in the context of a cell there'll be vibrations from all these molecular motors, some of them are going to be tiny, some are going to be bigger, how do you distinguish.
Interviewee - Philip Robinson
This is a proof of concept. They haven't used this to listen to cellular processes, all they have shown so far is they can listen to a single sound source.
Interviewer - Chris Smith
So, you're watching the nanoparticle vibrating because it is picking up the vibrations from whatever the source is and you can infer what the movement of that source must be based upon what the nanoparticle does
Interviewee - Philip Robinson
You're quite right. You're quite right. So they literally look at the nanoparticle and they look at the way that it moves under the influence of the sound vibrations. Of course, it moves all the time anyway even without the sound vibrations just due to normal Brownian motion. So what they have to do is disentangle that motion from the motion caused by the sound wave, which they managed to do very effectively. They measured a number of sound waves and showed that the particle is capable of hearing these different waves, but again they have not actually used it to listen to a sound and as you have pointed out there are a number of other considerations that might make it difficult to do that. You have sensitivity issues for one thing. The size of a nanoparticle and exactly how it can find it's the strength of the branch as you put it will all affect how effective this still be.
Interviewer - Chris Smith
I'm still blown away by the prospect of what you could do then, it sounds extraordinary, but is it likely to be practically useful?
Interviewee - Philip Robinson
Well, there are at least a couple of people who think so. Some experts I talked to when I was looking at this story, they say that the possibility of listening to cellular machinery is indeed feasible. Of course, it depends upon, again how energetic these noises are, can they be heard above the normal Brownian noise, but it's certainly a possibility.
Interviewer - Chris Smith
Phil Robinson.
Jingle
Interviewer - Chris Smith
You're listening to Chemistry World with me Chris Smith. Still to come, how scientists stumbled upon the ancestor of our RNA who might have helped to kick start life. Before that, you know that grease proof paper that your lunch comes wrapped in, the stuff you throw in the bin and you don't eat. Yes, that. Well the chances are you're probably eating and metabolizing a whole lot more of the fluorine rich material in there than you might think. Scott Mabury.
(19:05 - Scott Mabury looks at the issues surrounding fluorinated chemicals making their way into the food chain)
Interviewee - Scott Mabury
For a good 15 years or so, we've been interested in generally the role of fluorine in influencing environmental fate of chemicals, both you know, human derived and naturally derived. Related to that is why are humans so contaminated with perfluorinated acids, these are carboxylic acids and have a chain of carbon and fluorine bonds. They are very persistent. We don't know any means by which Mother Nature has to degrade them, so they do stick around for a long time. Humans have relatively high concentrations in parts per billion in our blood, these perfluorinated acids with carboxylic acids and sulphonic acids, sometimes called PFOS, we've made a number of discoveries of other fluorinated compounds. Some of which are actually compounds in commerce, commonly used chemicals that humans are routinely exposed to including these PAPs, these are perfluorinated alkyl phosphates or phosphinates. They're food contact paper chemical industry, puts them on paper to impart wonderful properties of both water and oil repellency. Originally the assumption was that these compounds stayed on the paper and if they didn't stay on the paper they weren't really bio-available and if they were bio-available they wouldn't stick around very long. It turns out when we actually look and develop the methods, in human blood we can routinely find these PAPs and PAPs-related kinds of chemicals of commerce in human blood in fairly high concentrations.
Interviewer - Chris Smith
So the big question is it's one thing to find them, it's another to actually say, well, are they safe or are they at risk?
Interviewee - Scott Mabury
The connection we're trying to ask is do the perfluorinated acids found in human blood, are they to some degree a result of and a product of the metabolic conversion of these PAPs chemicals and it was a bit of surprise to us that we found PAPs in human blood samples of fairly high concentrations despite the fact that they're, you know, fairly quickly removed. So, that suggests a consistent and ongoing source of exposure, Results in rat studies and in correlation looking at human blood samples, do suggest that a significant proportion of the perfluorinated acids themselves are actually produced in situ, in humans through metabolic processes converting these PAPs chemicals into the perfluorinated acids.
Interviewer - Chris Smith
So, they're not the metabolically inert things that we thought they were. They do actually engage in metabolic pathways. They are further modified.
Interviewee - Scott Mabury
Well, the perflourinated acids themselves do not, but they're the result of metabolic transformations of chemicals that we never would've thought would've been in human blood in the first place.
Interviewer - Chris Smith
So, what are you finding when you follow these things up, what's the outcome?
Interviewee - Scott Mabury
Well, the thing we're interested in is actually the PAPs themselves are phosphate esters, the metabolism of that in itself is super interesting, but it's actually the products of that on the way to the perfluorinated acids that we are very interested in, these intermediates. We have tested some of them, their toxicity against daphnia magna, you know, the common water flea often usually the canary, you know, of surface waters and found them to be really quite toxic and quite biologically hazardous.
Interviewer - Chris Smith
What did they do, in what way are they dangerous?
Interviewee - Scott Mabury
Their intrinsic reactivity is electrophiles and reacting with hopefully glutathione that's a common chemical in mammalian system that protects us from reactive electrophilic chemicals. So, it's a protection mechanism. But if glutathione isn't around then other things could react and you have the potential for disruption of protein enzymatic or cellular function.
Interviewer - Chris Smith
So, given the ubiquity of these things, and what you're finding in terms of what they might be able to do in the body, what is the implication given the huge burden of these things that are out there in the environment? Is there anything we can actually do about it?
Interviewee - Scott Mabury
Well, they're used on food contact paper, you know, as a consumer chemical. We can move to alternatives. With a
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