Chemistry World Podcast - April 2011
1:13 -Molecules that walk, hop and jump
4:44 -Diagnosing diseases with CDs
7:00 -James Landers tells us how to streamline forensic DNA profiling with microfluidics
14:30 -Sensitive TB diagnosis using sugar
17:05 -Harvesting energy from soft drinks
19:25 -Zhong Lin Wang on picking up good vibrations to harvest energy from the environment
25:20 -Earth's missing xenon could be hiding in quartz
28:45 -To thicken up runny liquids, add fluid
32:10 -Trivia - how much excess phosphorus from fertiliser runs off fields and into waterways, and how might we conserve this endangered element?
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
Interviewer - Chris Smith
Hello welcome to the April 2011 edition of the Chemistry World podcast. With me this month are Phil Broadwith, Mike Brown and Elinor Richards and they're here to talk about how a modified CD can be used to count blood cells, a wait around your iPod on fizzy drinks and how adding water can make some fluids thicker, which turns out to be ideal for the diet industry.
Interviewee - Phillip Broadwith
If you think about wanting to diet, you still want to eat the same amount of food and feel full so you won't feed that will fill your stomach but not necessarily have the same calorie effect or fat content. So you get the same kind of fullness and pleasure from eating it but without the pain on the other side.
Interviewer - Chris Smith
So why sell food when you can sell water? Sounds ideal for supermarket and brand products, doesn't it? I'm Chris Smith and this is the Chemistry World podcast.
(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)
(1:13 - Molecules that walk, hop and jump)
Interviewer - Chris Smith
And with a hop, a skip and a jump we're off with the first story, Mike.
Interviewee - Mike Brown
Okay Chris, Jurriaan Huskens and his colleagues at the University of Twente in the Netherlands and his collaborators at the University of Cork in Ireland have been looking at how molecules, dye molecules move across the surface.
Interviewer - Chris Smith
So how do they do it, what are they looking?
Interviewee - Mike Brown
They've taken dye molecules with two legs and they've got a surface, a monolayer surface of beta-cyclodextrin which is a ring-type structure and they put them onto the surface rather like you would see tires in a obstacle course, so you have to put your legs into each of the tires as you walk down the obstacle course and what they've done is they've positioned the molecules at one end and they've seen depending on the concentration of competing cyclodextrin so free cyclodextrins in the solution around them, they've seen how the molecules move across the surface and they've found that there are three mechanisms for this.
Interviewer - Chris Smith
So do those competing molecules effectively stand in the tires as well, so they stop the molecule that you want to walk getting its feet into those holes? So how it works?
Interviewee - Mike Brown
And they compete for the feet of the molecules and then other molecules, other dye molecules also fit in the monolayer holes as well, so you've got competing from other dye molecules on the surface and competing from the cyclodextrins holding onto the feet in the free solution.
Interviewer - Chris Smith
And how do they watch the walking?
Interviewee - Mike Brown
They use fluorescent microscopy to see what's going on in the solution, so what they've found is that if you have got a high concentration of competitor molecules, so you've got a high concentration of cyclodextrins floating around in a solution and also dye molecules on the surface locked in, then the molecules actually lift off the surface, float through the surface and then plant themselves somewhere else, so they're actually flying through the solution. In contrast, when there's a low concentration of competitor molecules the molecules pick up one leg and move to the next one next to them and so they walk across the surface.
Interviewer - Chris Smith
But why do they make these movements at all?
Interviewee - Mike Brown
They're actually moving spontaneously, they've got weak interactions between the surface and the legs and they spontaneously move one leg at a time. It depends on if both legs happen to move at the same time, then they'll float through solutions well.
Interviewer - Chris Smith
And the third way.
Interviewee - Mike Brown
The third way is when you've got a medium amount of competitor species, so a medium amount of the cyclodextrins. One of the feet on the molecule would detach from the surface and actually lock into one of the free cyclodextrins and the other foot will actually move along the surface. You actually hop along the surface. So, you've got one mechanism where you're walking and one way you're hopping and one way you're jumping and flying through the solution.
Interviewer - Chris Smith
Oh, very elegant but why is this is helpful, what does this teach us?
Interviewee - Mike Brown
Okay, so the research team wanted to look at how molecules move across the surface and bind because they're looking at a bigger picture of how bacteria and viruses bind to cell membranes depending on the concentration of the viruses or the bacteria at the cell membrane. They're actually seeing how possibly these interact and how you know diseases take over cells and things like that.
Interviewer - Chris Smith
So you could say research to die for. Thank you Mike. Elinor tell us about this one, this is fantastic, so you've heard of self-help books and CDs, now you're telling that you can diagnose yourself with a CD.
(4:44 - Diagnosing diseases with CDs)
Interviewee - Elinor Richards
Yeah, that's right. A team of researchers in the US led by Gang Logan Liu have integrated microfluidic device, on top of it, just playing normal digital compact disc, the device that analyze cells, you can insert the disc into just plain old standard computer disc drive for analysis and this could be used to diagnose diseases.
Interviewer - Chris Smith
So let me get me straight, they take a CD or what would be a normal CD and instead of the sorts of the laser track inside, they've replaced this with a microfluidic device which you can put something into that track.
Interviewee - Elinor Richards
Yes that's right, what they've done is they've burnt a data file onto the CD consisting of a sequence of binary numbers and then on top of that they've added the microfluidic layer with channels and then they inject the fluid samples into these channels and then they pop it into the computer.
Interviewer - Chris Smith
This is for real not an April fool.
Interviewee - Elinor Richards
It's not, it's for real.
Interviewer - Chris Smith
So you put it into the CD drive and the laser which would scan the data track then also goes through the micro fluidic device and hits the cells that are going to be in there.
Interviewee - Elinor Richards
It does, yes. So as the laser is reading the binary data it produces a graph or a read out and then when it hits the cells it interrupts the readout. You've got the reading on the graph so you can tell what the cells are.
Interviewer - Chris Smith
Oh, so you effectively get a breakdown in the data and so it knows that whether it's not reading data that must be a cell.
Interviewee - Elinor Richards
Yes, yes.
Interviewer - Chris Smith
So it can count the cells and also size them
Interviewee - Elinor Richards
Yes, it can yes.
Interviewer - Chris Smith
Bligh me, so this actually work, what can you do with it, what sorts of cells.
Interviewee - Elinor Richards
It does blood cell counting and sizing and .
Interviewer - Chris Smith
So what do they say you could do with it, you do sort of diagnosis at home with your own PC.
Interviewee - Elinor Richards
Just using at home for personalised medicine and maybe so you can put your own sample into it popping in the PC and then let the doctor know the results.
Interviewer - Chris Smith
(Laughter) Fantastic! That's got to be one of the best stories I have ever heard and of course presumably that any CD player will read it, just it's the disc that a special thing so that's what they're going to market.
Interviewee - Elinor Richards
Yes.
Interviewer - Chris Smith
And that CD comes with a bonus musical track too we are told by Soft Cell, no just kidding that really is an April fool, thanks Elinor. But speaking of microfluidic devices, University of Virginia scientist James Landers has found a way to bring the molecular biology laboratory down to the size of something you can hold in your hand.
(7:00 - James Landers tells us how to streamline forensic DNA profiling with microfluidics)
Interviewee - James Landers
So the applications are really numerous, at the outset of microfluidics in the early 1990s, we are really focussed on clinical, the idea that you can now through reducing the volume of reagents needed, the volume of sample needed, drastically reduced turnaround time on clinical assays and so the initial goal was bring this into the clinical world where you can now take the two or three day assay that is done in the clinical lab that looks at a molecular defect in DNA or in proteins and now do that in an hour which brought you into the realm of potentially point of care testing or now rather than sending a sample off to a central testing lab you could now do that in the doctor's office and this dramatically changes how physicians would practice, rather than having somebody come back a week later for a result, you talk about the patient waiting out in the waiting room and coming back in at 45 minutes and talking about the result from the test. There's also been a massive growth and interest in applying this to forensics primarily for the application to forensic DNA testing. Their turnaround time is critical and you can only hold somebody for so long if it takes 10 hours to get a result and you can only hold them for a period of time that is substantially shorter than that, that's a problem, there is also the cost of holding people.
Interviewer - Chris Smith
And also I guess there's the whole question of change of evidence because in the lab in which I work, we occasionally do handle specimens which are from crime scenes and we have to have senior people continuously scrutinizing and shepherding a single sample through the laboratory in multiple different steps which takes up a senior person's time for a whole day or even longer. If you can do the whole thing on one analytical platform, one chip or one microfluidic device where only one person has to put that in a machine and the whole thing gets done A quickly and B in one go, no transfer. That's going to be better from a forensic point of view too.
Interviewee - James Landers
Yeah, now, that's a great point Chris because and it's a great point for two reasons. The first one is the chain of custody issue becomes a non issue primarily because it's a closed system, once the sample goes in, there's no opportunity for essentially intersteper or inter step, loss of chain of custody or mixing up of samples. The second one is, issue of contamination and there are two different spins on this. The issue of contamination from a forensic point of view is once the samples in the close system of the microfluidic device you minimise if not completely obliterating and the opportunity to contaminate any part of that process with exogenous DNA which from a defence point of view, you know, defending this in court is critical. If you flip that to the clinical side, it's actually a different reason that you want to have a contamination free type of system and that is if you now have patient blood potentially from patients who are infected with various infectious agents you now want to minimise the exposure of the lab technician to what's in the chip and so you minimise contamination for those two applications in very important ways.
Interviewer - Chris Smith
Well I am sold on that, so tell us about the technology though, how did you manage to do this? What were the big obstacles you have to surmount to deliver this platform?
Interviewee - James Landers
The platform is still under development with a collaboration between the University of Virginia, ZyGem MicroLab and Lockheed Martin and we're building and testing a baby unit right now and the challenges are number one, building three instruments into one and making sure it's not the size of a mini Austin, the other is when you're dealing with 25 microlitres of a PCR master mix that's the volume to surface area ratio is very large. When you shrink down now that volume into a half a microlitre or less, the surface area to volume ratio has essentially been elevated, sometimes order of magnitude and now the issues associated with components, critical components in that very small volume sticking to the wall and essentially being deactivated or lost becomes very critical and PCR simply doesn't knock it out. The other types of issues that you deal with is that the fact you now have to keep different chemistries divided when needed but intimately, fludically connected when you want. So for example, if you do just conventional solid phase extraction in a micro device using silica beads and guanidine and isopropanol, those two components are PCR inhibitors if you now contaminate the downstream PCR architecture with even nanolitre quantities of those reagents and so the challenge was how do you keep them divided while you're doing the independent processes but open them up when you need to transfer the purified DNA. The last one I would point to Chris is how do you make this cost effective? If you can now take a US$100 to do a DNA fingerprinting on a sample here in the US, and you can now do it in an automated closed system that gets you around the chain of custody issues that you described and make it rapid what if somebody won't pay for that, are they willing to pay for 100 dollars probably not? So how do you now do that so that it is at least the same cost as current technology except with all of the advantages of speed and smaller volumes and then how do you make it less expensive, ultimately what you want to do. So I think those are the challenges both at the physical limits but also in terms of mass production and cost of the user.
Interviewer - Chris Smith
What about time to market, how far away are you from being able to unleash this saying here we go. We have quality control, quality shop product that can be used for all this different applications.
Interviewee - James Landers
That is the 64-thousand dollar question and ZyGem MicroLab and Lockheed are building our own schedule for what would be a pre-production unit this fall and how far beyond that I would hope no more than another year or two, so realistically within the next two years we hope to be able to have this placed in a number of labs where people are essentially testing it with their normal number of samples coming in and the normal kind of workflow that they have.
Interviewer - Chris Smith
Size really is everything that was James Landers from the University of Virginia. He's also the Chief Scientific Officer of ZyGem MicroLab the company developing that technology.
Jingle
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Interviewer - Chris Smith
You're listening to Chemistry World, with me Chris Smith. Still to come, a new device that can generate electricity by extracting energy from tiny air currents and also where's all the earth's xenon gone. First though TB or not TB. Scientists have got a new diagnostic trick to pick up tuberculosis infection, Phil.
(14:30 - Sensitive TB diagnosis using sugar)
Interviewee - Phillip Broadwith
Yes Chris, well one of the hardest things about TB is actually diagnosing the disease according to the World Health Organization maybe a third of the world's population is infected with tuberculosis but only 5 to 10% of infected people ever become sick and working out who the people carrying the disease are would be a phenomenal breakthrough for medicine would allow people to get treated and we could start eradicating the disease.
Interviewer - Chris Smith
It is something like 10,000 deaths a day, I mean, 10,000 new infections everyday I mean it is tremendous problem especially in sub-Sahara in Africa.
Interviewee - Phillip Broadwith
Yeah and a lot of them don't even know, so passing it on to new people all the time.
Interviewer - Chris Smith
So what are these guys doing?
Interviewee - Phillip Broadwith
So what Clifton Barry at the US National Institute of Allergy and Infectious Disease in Bethesda and Ben Davis from the University of Oxford in the UK have done is used Trehalose which is a sugar that isn't used, isn't found in mammalian cells only really in bacteria and plants to label TB to make it easier to diagnose.
Interviewer - Chris Smith
So how does it work, talk us through the process what they're actually doing and how they actually make the diagnosis?
Interviewee - Phillip Broadwith
On the surface of the tuberculosis bacteria there are some enzymes that are involved in building up its cell wall and they use this sugar Trehalose to do that and so what Ben Davis' group did was to make various different modified versions of Trehalose to see if they could inhibit those enzymes as potential drugs but one of the modifications they made was to put fluorescein a fluorescent molecule on so that they could actually see whether it was being taken up.
Interviewer -Chris Smith
I see, so the fluorescein is linked to the Trehalose so if the bacteria take up and use the sugar and incorporates into the cell wall, they'll be incorporating fluorescein with it so the bugs are going to glow.
Interviewee - Phillip Broadwith
Yeah, exactly the bacteria that have taken up this Trehalose sugar then glow. You can just take any sample that has the TB bacteria in it, feed them loads of sugar. If they take the sugar up then they glow and you get a very easy to read indication of the TB there.
Interviewer - Chris Smith
Sounds encouraging and I guess pretty simple could be used especially in third world countries where TB is a real problem.
Interviewee - Phillip Broadwith
Yeah absolutely, you don't need too much specific equipment. You just need some way of detecting the fluorescence and what Clifton Barry says that is that he had already started using the technique on patient samples in South Korea.
Interviewer - Chris Smith
So we have to just watch this space and find out whether or not it turns out to be successful. Thanks Phil. While talking of sugary things and sweet stuff, Elinor a device, and you've got all the best stories this month, a device that will turn waste food drinks whatever into energy. This sounds like the back to the future that was Mr. Fusion on the car and back to the future that ran on Yogurts and banana skins and things. What's this all about?
(17:05 - Harvesting energy from soft drinks)
Interviewee - Elinor Richards
Well that's good, can you imagine if your iPod runs in batteries in the future and you can just open your can of drink and charge it.
Interviewer - Chris Smith
So I am in, so go on. How does this work then?
Interviewee - Elinor Richards
Scientists in China at the Chinese Academy of Science in Beijing led by Shaojun Dong, they made a bio-fuel cell that actually harvests energy from soft drinks which is ice tea and juices.
Interviewer - Chris Smith
Excuse the terrible pun, but what's the potential here, I mean what could you do with something like this because you know outline how much energy it will produce, presumably not very much?
Interviewee - Elinor Richards
Not very much but just one ml of drink could allow the fuel cell to provide electrical energy for over a month.
Interviewer - Chris Smith
Well!!!
Interviewee - Elinor Richards
But that's for small devices.
Interviewer - Chris Smith
Sure so how does it actually work. What are the nuts and bolts in there?
Interviewee - Elinor Richards
Okay, so you've got a bio anode and a bio cathode and these are made from carbon fibre electrodes and these have been modified with carbon nanotubes and they've been modified again with enzymes. So the anodes, the bio-anode modified with enzyme, oxidises the glucose in the soft drinks and the bio-cathode reduces the oxygen in the air to water. And these two reactions then power the device.
Interviewer - Chris Smith
And you could run on anything with glucose as a source then?
Interviewee - Elinor Richards
Yeah, so some of the examples here they've used ice tea, vegetable juice, fruit juice.
Interviewer - Chris Smith
But where do they see this actually being applied really, because obviously there are devices that people have put into the human body which are powered by glucose in the bloodstream, this is externalizing that and the same that we could use the same thing with devices outside the body.
Interviewee - Elinor Richards
Yes, the team do say that they could use importable power sources and implantable medical devices because they generate more power than other bio-fuel cell types.
Interviewer - Chris Smith
I see, do you know how far along the production line or in development is this. Is this just proof of concept or is it being taken to market soon?
Interviewee - Elinor Richards
Well the team is working on improving the bio-compatibility and the long term stability of the implantable miniature bio-fuel cells.
Interviewer - Chris Smith
So you save money on batteries but end up spending a fortune on fizzy drinks instead? Maybe there is a way to have a free lunch after all.
(19:25 - Zhong Lin Wang on picking up good vibrations to harvest energy from the environment)
Interviewee - Zhong Lin Wang
My name is Zhong Lin Wang. I am a Chair Professor at the Georgia Institute of Technology, Atlanta Georgia. My research in the past has been involved to harvest energy from environment to power small electronics. In the past we've spent a lot of time to develop nanotechnology, nanosensors, something small, better, high performance, lower power consumption but when the system becomes smaller enough the battery used to drive the system is comparably large.
Interviewer - Chris Smith
So, on the one hand you're shrinking things down to the tiny scale and then completely off-setting all the benefits by having a gigantic battery attached to it which then completely negates all the benefits of being small.
Interviewee - Zhong Lin Wang
Exactly, so we want to make a small system that include a battery and our idea that can we get rid of the battery that harvest energy from the environment, well, energy we have solar, mechanical, thermal chemical but when the device becomes small the working environment may not have the solar energy available. Somehow electrical won't work because there's no temperature gradient so we looked at mechanical energy like vibration, the voice, like you and me talk, our voices have vibration and for example in a biomedical system muscle stretching or blood flow all this is mechanical, can we convert this into electricity to ply these tiny devices.
Interviewer - Chris Smith
And how were you doing this, what's the approach?
Interviewee - Zhong Lin Wang
The process that we use effect is called piezoelectric effect this is that for certain crystal that does not have a central symmetry when you apply a strain or force the ions in the crystal polarise to produce an electric field inside the crystal. Once you change the strain applied to the crystal back and forth and you drive the electron to flow back and forth, that's the mechanism we convert mechanical deformation into electricity and what is the efficiency? Our measurements show we can achieve 7% efficiency today. Then why nano-materials? Because, if you have a gigantic physical motion, you have a larger pressure, larger force, you can do it but we talk about leaving environment, something very tiny, very mild can you do that? So we use nano materials the reason that nano materials have small dimension, they can respond to this kind of mechanical triggering at a very small magnitude.
Interviewer - Chris Smith
So what you're doing, massive parallel arrays so that although an individual component will only generate a very tiny current if you have many of them in parallel all extracting energy from the local environment you can add that together to produce a much bigger potential. Is that how you are doing it?
Interviewee - Zhong Lin Wang Absolutely. Let me start with the materials, we called this nanowires. We use zinc oxide which is a biocompatible environmentally green material and are very cheap too. So once you have this little nano wires, you have mechanical deformation, you produce a potential but one wire is not enough so we would be developing a technology we integrate the constitution of millions of this nano wires on a little tiny area to form array, so that we can produce today up to 5 to 10 V output and the size of it is a fingertip size and a power which microvolt and even mill volts range and so what that mean. Let's say if you reach to micro volts to mill volts a lot of thing can be proven. Let's from the thing we're familiar with, like iPods in order to drive an iPod you need about 50 mill volt energy drivers. Today we've already reached a couple of mill volts so we are not too far away from driving iPod where iPod is a big you know is a big unit. If we can drive this, we can drive a lot more smaller units.
Interviewer - Chris Smith
That's amazing, so how do you actually make these arrays, these nano wires and then couple them to get the energy out?
Interviewee - Zhong Lin Wang
This is the key because and we have two ways to make it, we have wafer phase, we also use chemical growth. We can grow on wafer level, use pattern technique arrays by simple solution chemistry at a temperature less than 100 degrees C and you don't need a clean room to do this kind of fabrication and the way you integrate them together is that if you have an array of nano wires, you build a bottom electrode, you have a top electrode. If all these wires work together the electrodes collects the charge from all of them.
Interviewer - Chris Smith
And what's the working lifetime of the material, how long will it continue to vibrate like this, in other words am I going to have to buy a new one of these every week to run my iPod in future, or is this going to last 10 years.
Interviewee - Zhong Lin Wang
We do the test, when you make a thing smaller tiny little nano wires, the mechanical robustness improve dramatically. Let's give you a number. We use nano wires; we put it on resonance this local vibration, we run it for 35 billion cycles to test. Is there any fatigue as a result of this? This shows this is basically fatigue free because of the small size at nano scale and we can make this work many, many, many cycles., 35 billion cycles is a lot of cycles you can
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