Episode 148      28 min 40 sec
Targeted delivery: The promise of nanotherapies in treating cancer

Chemistry Associate Professor Eva Harth and Chemical Engineer Dr Angus Johnston discuss how cancer treatments may be vastly improved through drug delivery at the nanoscale. With science host Dr Shane Huntington.

"If we attach these antibody Y-shaped molecules to the surface of the capsule, they will then specifically stick to the cancer cells and go inside the cancer cells, rather than going to a healthy cell." -- Dr Angus Johnston





           



Assoc Prof Eva Harth
Associate Profesor Eva Harth

Eva Harth was born in Cologne, Germany and studied chemistry at the University of Bonn and the University of Zurich, Switzerland. In 1994 she joined the group of Prof. K. Muellen at the Max Planck Institute for Polymer Research, obtaining her PhD in 1998 for work in the area of fullerene adducts and polymers. A postdoctoral fellowship with CPIMA (National Science Foundation - Center for Polymer Interfaces and Macromolecular Assemblies) brought her to the IBM Almaden Research Center, California USA, to work under the direction of Prof. Craig J. Hawker focusing on the development of new living free polymerization techniques and approaches to nanoscopic materials. In 2001 she joined XenoPort, Inc. as a Staff Scientist investigating enabling technologies for the increased bioavailability of macromolecular therapeutics. After the extensive industrial experience she started at Vanderbilt University as Assistant Professor in the Department of Chemistry in 2004 with a secondary appointment in the Department of Pharmacology, Vanderbilt Medical School and was promoted to Associate Professor in 2011. In 2007 she was awarded with the NSF CAREER Award for young faculty and her research advances delivery technologies across challenging biological barriers and towards highly vascular tumors.

Dr Angus Johnston
Dr Angus Johnston

Angus Johnston is a research fellow in the Department of Chemical and Biomolecular Engineering at the University of Melbourne. After completing his PhD in 2006 on the preparation of novel materials for rapid DNA sequencing from the University of Queensland, Angus moved to Melbourne to work in the Nanostructured Interfaces and Materials Group. His current research investigates targeted drug delivery systems, utilising nano-capsules to specifically deliver chemotherapy drugs and gene knock-down constructs to cancer cells. His other reseach interests include nanoengineered thin films and molecular sensing techniques. Angus has received a number of awards for his research, including the 2010 Young Tall Poppy Science Award from the Australian Institute of Policy and Science.

Credits

Host: Dr Shane Huntington
Producers: Kelvin Param, Eric van Bemmel
Audio Engineer: Gavin Nebauer
Episode Research: Dr Dyani Lewis
Voiceover: Dr Nerissa Hannink
Series Creators: Eric van Bemmel and Kelvin Param

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VOICEOVER
Welcome to Up Close, the research, opinion and analysis podcast from the University of Melbourne, Australia.

SHANE HUNTINGTON
I’m Shane Huntington. Thanks for joining us. The effective treatment of a range of human ailments depends heavily on our ability to deliver appropriate drugs and therapies to specific areas of the body. In the case of cancer treatment, the desire is to kill the cancerous cells as effectively as possible. Currently, this is done at a significant disadvantage to the overall health of the patient, as the drugs used cannot be targeted to cancerous cells alone. As we move down to the nanoscale, we find new and exciting possibilities. At this scale, material properties differ from those of bulk materials of the same chemical make-up.
Today on Up Close, we are joined by two guests to help us explore the world of nanoscale therapeutics. Eva Harth, Associate Professor of Chemistry at Vanderbilt University, Nashville, Tennessee, and Dr Angus Johnston, Research Fellow at the Nanostructured Interfaces and Materials Group in the Department of Chemical and Biomolecular Engineering here at the University of Melbourne, Australia. Eva Harth joins us from Nashville via a Skype connection. Welcome to Up Close, Eva and Angus.

ANGUS JOHNSTON
Good to be with you.

EVA HARTH
Thank you so much.

SHANE HUNTINGDON
Eva, I’d like to start with you. If you wouldn't mind giving us an idea of what the term nano actually refers to and how this is significant on a biological scale.

EVA HARTH
This is actually the scale where a lot of biological systems interact with each other. So for example, a virus has, for example, a scale of 50 nanometres, where an DNA string, so between the strings it is two nanometres. So it is found that, specifically in the nanoscale, when we build artificial structures, we can also interact with biological structures very well. So it is not just to be fancy. It is really the optimum scale where you can apply, for example, also cancer treatments. But I have to say that, inside of the nanoscale, this is actually a very wide range. And specifically for cancer therapy, you have to work in a very specific scale inside of the nanoscale as well.

SHANE HUNTINGDON
Okay. Angus, can you give us an idea of what are the sort of main limitations that we find at the moment with current therapies that we think will be able to be overcome with this type of research?

ANGUS JOHNSTON
So one of the major issues with things like chemotherapy is the drugs that we use are really just very toxic compounds. And the principle is that cancer cells are growing much faster than a lot of other cells in the body and so they’ll take up more of this toxic compound and die first. But one of the limitations is that any cell that is taking up material from its surroundings also takes up this toxic compound. So I think everyone’s familiar with the side effects of chemotherapy where you lose your hair and things like that. And so what the goal is with these nanotherapies is to try and deliver the drug in a more intelligent way. So we only deliver the drug to the cancer cells or the cells that require this therapy, rather than delivering it systemically throughout the entire body.

SHANE HUNTINGDON
Angus, just following on from that, we’ve been hearing this term nano now for, well, more than two decades at least and quite a while. Are there drugs that are currently in use that actually utilise these nano features that are in the marketplace?

ANGUS JOHNSTON
There's two reasonably widely used examples of nanotechnology based drugs, the sort of first generation of these materials. One of them is called Abraxane and the other one is Doxil. They both take commonly used anti-cancer drugs and try and formulate them in a different way to be part of a nanoparticle, as Eva says, in this size range of around about 50 to 100 nanometres. And so what these do is they effect the way the drug is delivered around the body. So in the example of doxorubicin, which is the cancer drug that’s put into Doxil, Doxorubicin itself accumulates in the heart. So anybody who has a weak heart or heart troubles, this makes it an ineffective treatment because you have very bad side effects with damage to the heart. So by giving the people Doxil, it takes the doxorubicin drug away from the heart and delivers it to other areas in the body. It doesn’t overcome the side effects. So there are still severe side effects associated with these drugs. But what’s hoped, in the next generation of these nano-engineered materials, is that you will be able to become more intelligent and not just say take it away from the heart but deliver it more to the tumour and where it’s required.

SHANE HUNTINGDON
Eva, you’ve been delivering a structure which you call a nanosponge. Can you give us an idea of what this is and how you actually go about fabricating such an item?

EVA HARTH
Yes. So you were just talking about Abraxane. So it is basically the same idea. So what Abraxane does, it also solubilises the cancer drug. So typical chemotherapeutics, they are very hydrophobic. That means that they are not very soluble in the body. Abraxane does already something that it solubilises more the cancer drug. The same thing we do with the nanosponge. But in contrast to the Abraxane, we can tailor this a lot better. So that means we can incorporate in this nanosponge a lot more drug and also we are very versatile in what kind of drug we can encapsulate. So it is not only limited to one drug.

So the nanosponge looks like a network in a three-dimensional form. So it is a globe. But what we can do is we can entrap the drug molecule in this three-dimensional network and then it is solubilised. This gives a huge advantage because then the drug is more available for the body and also it is more protected and it can stay around for a longer time. On top of this, since it is a synthetical network, you can do chemistry with it. So you can add units, so we call them targeting units, that guide the entire nanonsponge with the drug encapsulated to the tumour site. So this leads to another effect that you don’t have to swamp basically the entire body with the cancer drug. So you guide basically this very potent package to the tumour site and then it can be released.
It’s a sophisticated thing and we have it designed specifically for cancer drugs. So we can tailor the release rate and many different things. But the entire idea was to get basically hydrophobic drugs, which are already on the market and don’t work that well because of their low solubility, into a higher solubility state and also guided to the tumour site, so that they can be active at that critical side.

SHANE HUNTINGDON
So in doing this, you’re essentially converting these cancer drugs so that they’re water friendly, as it were. The body is primarily water, in many regards. How much of this drug can you actually get into these nanosponges? What’s the process of actually loading the sponges up with the drug?

EVA HARTH
So we make this nanosponge first and then we can load the drug in. So we do this in organic solvents. So we solubilise the particle in an organic solvent and also the drug. We bring the two solvents together. Then we mix it. Then the entire system is then crashed out in water. This is sort of a freeze mechanism. So in that moment drugs are inside of this nanosponge. Then we can collect it and purify it and wash it with water. And we get actual 15 weight per cent of the drug into the nanoponge, which does not sound a lot. But other controlled drug release systems, which are made currently as well, they have typically a lower loading. So we are very happy about this kind of scale of loading actually.

SHANE HUNTINGDON
Eva, when it comes to the actual manufacture of the nanosponges, I assume this is I guess what people would refer to as bucket chemistry. You’re not making them one at a time, are you? You’re making a very large number at once.

EVA HARTH
Yes. So we have developed a one-prod procedure. I have actually undergraduates making this already. So it is a very practical synthesis. But I have to say I mean we work already since six years on this, so we have optimised this procedure. But it is a very practical procedure and it is based on an intermolecular chain collapse process. I know that sounds very complicated. But it is actually a cross-linking mechanism. So you bring two parts together, a longer string and a shorter string. There they can react with each other, but in a very controlled manner. Then you form this very controlled network which you can control in the density of the cross-linking and also in the size. This feature, these determine how fast the drug is released and how fast the entire system degrades to release the drug. So we can tailor all this.
Here comes then the interesting part because we can tailor this basically for each patient. So this would be the example of the first personalised drug release system because every disease state is different, every cancer is different, even every patient is different. So we can respond to that. So we can release the drug faster. With this we hope that we can avoid also the multi-drug resistance or that we can deliver the right amount of drug to the cancer site. So this is very, very critical.

SHANE HUNTINGDON
That sounds excellent, Eva. Angus, let me turn to you now because you use a somewhat different model. Now my understanding is your nanoparticles are more like hollow balls. Can you describe what you’re working on and how you go about fabricating these?

ANGUS JOHNSTON
Yes, sure. So we use a process called a layer by layer process, where we build up very thin layers of material, one layer at a time. The way we do this is we start off with a template particle, which can be sort of any size from down to a couple of nanometres, say five nanometres in diameter, all the way up to a couple of microns, which is sort of like a tenth the width of a human hand. What we do is we deposit this polymer onto the surface. What happens is, in the simplest example of getting these materials to assemble, we take something with a positive charge and it sticks to a negatively charged surface. Then you can put a negatively charged material on top of your positively charged material. So it’s sort of like how magnets interact with each other. You can get the molecules to interact with each other. So you can build up very thin layers, one layer at a time.
What this gives us is very fine control over the materials. So if we want to have certain degradation properties, so the way it releases within the body, we can engineer this by putting different materials in at different layers. Then, at the end of this process, if we’ve used a template which can be dissolved, so a sacrificial template, it dissolves out and then you end up with a hollow capsule. It’s this hollow interior that the drug can be loaded in.

SHANE HUNTINGDON
Again, with regards to the loading process, how much of the drug can you get into these very small objects?

ANGUS JOHNSTON
So it depends a bit on the drug and it depends on the actual application. So for instances like cancer therapy we obviously want to have as much drug inside as possible. So we can put things - like Eva was saying, a lot of drugs are very water insoluble. So we can put a very small oil droplet inside our capsules and then this will hold a significant amount of drug. For other things like DNA, which is used for gene therapy, it is much better if it’s kept in a water environment. So per capsule, we can encapsulate up to 10 to 100,000 individual DNA strands per capsule. Then the idea is that, if the delivery is very targeted, so you are only delivering to the cells that it’s required, the actual total amount of drug that you’ll deliver to a patient will be significantly less because you’re not wasting a whole heap by going to all the other organs. It only ends up in the relatively small number of cells that you’re trying to deliver to.

SHANE HUNTINGDON
This is Up Close, coming to you from the University of Melbourne, Australia. I’m Shane Huntingdon. Our guests today are Associate Professor Eva Harth and Dr Angus Johnston. And we are discussing cancer therapy at the nanoscale.
Angus, what kind of chemical properties do these nanoparticles actually need to have in order to be therapeutically useful?

ANGUS JOHNSTON
There's a couple of things that you need to have for these capsules. The main one is obviously bio-compatibility. So it needs to be something that the body isn’t going to react adversely to. There's a number of ways that this can be achieved. Typically it’s done by putting certain polymers which will interact with the body in a very minimal way so you don’t get a lot of uptake by certain cells of the immune system which are basically designed to clear foreign material.
One of the other important properties of these materials is that, if you’ve encapsulated a drug, you have to be able to release the drug. So it doesn’t matter how much drug you’ve encapsulated in something, if you’ve encapsulated it so well that it never comes out, then it’s got no use. So there needs to be some sort of mechanism for the drug to be released now. In certain instances, you want the drug to be released slowly, over an extended period of time. On other instances, you require a burst release. So basically once it’s into the cell you want all your drug released. And these different properties can be engineered through a number of different mechanisms, either with our systems or the system that Eva’s talking about.
Then I think the final thing that’s very important and which is what people are looking at as the next generation of materials is that there's this targeting ability. So rather than just having them sort of floating aimlessly around the body, you put something on the surface of this capsule or sponge which will sort of seek out the cancer cells and bind specifically to these cancer cells and only stick to those cells rather than the healthy cells.

SHANE HUNTINGDON
Angus, I can imagine, with all the targeting and so forth, I guess efficiency is sort of an interesting concept with regards to the drugs themselves. But in this loading process, how efficient is that with regards to the drugs you’re using? Is there a very large amount of loss? Some drugs are quite expensive.

ANGUS JOHNSTON
Yes. A lot of the techniques that have been developed recently sort of focus on the fact that a lot of these drugs, particularly things that relate to DNA, are very expensive. So with some of our systems, what we call the encapsulation efficiency, so basically the per cent of drug that we try and put it, the amount that actually ends up inside our capsule, can be as high as 80 or 90 per cent. That’s for sort of certain drugs. Other drugs, a lot of the anti-cancer drugs for our system our efficiency is somewhat less. It’s sort of down to the 10, 20 per cent. But if we think about it in terms of the overall efficiency, the goal is that you maybe only giving one per cent of the dose that you would currently give. So, even if you’re only getting 10 per cent encapsulated, it still is a reasonably good improvement.

SHANE HUNTINGDON
Eva, when we talk about the way in which we put these nanoparticles into the body and they go to specific areas of need, how is that actually occurring? I mean, we’re still, to some degree, at the mercy of the body to carry these materials around. So how do we go about making sure that they get to where they’re intended?

EVA HARTH
Yes. So we are working still with IV injections. So it is not oral delivery. So it is directly into the bloodstream. Here, the targeting unit plays a critical role. So the targeting unit has to be very, very efficient. The targeting units we are using, these are peptides. There are a number of different peptides which we tried. What these peptides do, they basically recognise receptors on the cancer cell. So a cancer cell is very different from a normal cell. In this way, you can really selectively target the cancer cell. There are a number of different peptides out there and they target different receptors.
Now you have to make the decision which kind of peptide you are using. Let’s just say that most of the peptides which are already very popular, they target the cancer cell very well. You can do animal studies to test these first and this is done. You can also determine, in this way, how fast the nanoparticle binds to the specific cancer cell. This is done by imaging. So you can get mice and you can inject it into the mice and then you can follow how fast the particle gets basically to the cancer cell. Then you can determine if this peptide which you chose is actually good enough. Some of the peptides, they target only a few cancers. But most of the time, every cancer they have the same receptors. So it is very often that when you choose one peptide that it targets actually a number of different cancers. So then this is very interesting.
But the other important part is how big your nanoparticle is. So we use a particle which is 50 nanometres in size. We found that this size dimension is ideal. When we go above it, we find also that the nanoparticle is kind of accumulated in the liver. So when you go over 100 nanometres. But when you work in this nanoscale dimension, we found no accumulation in the liver and it goes in 12 hours to the tumour site. This is a really promising result.

SHANE HUNTINGDON
When you speak about the nanoparticle actually reaching its destination, what is actually happening to the structure of the nanoparticle? I understand that the drug is being released at that point, but what happens to the structure of the nanoparticle itself?

EVA HARTH
Yes. So we have done experiments that we showed that the peptides, the targeting peptide guides even the particle into the cancel cell. Since the nanoparticle is in an organic network, it is a polyester and it can be hydrolysed. So when it is around water, it will be chewed up. So it is completely degradable. So the nanoparticle will degrade into little pieces. In metabolism studies, you can find out how long this particle will be around in the tumour or maybe also in any other organ. But we have not observed this yet. But this entire system is basically degradable and then it can be excreted.

SHANE HUNTINGDON
Angus, can you describe the surfaces of your drugs, what those chemicals are that allow them to go to the specific locations in the body that you need them to go to?

ANGUS JOHNSTON
Yes, sure. So like Eva was saying, there's a number of different targeting molecules that can be used. There's the peptides, which are short, basically short protein fragments which are made up of individual amino acids or you can use an antibody which is a particular molecule that’s naturally generated by the immune system, but we can, with our biological collaborators, basically generate antibodies that are specific to certain types of receptors on cells. So we work with the Ludwig Institute for Cancer Research, who are developing antibodies for colorectal cancer. So an antibody is a protein that’s basically a Y-shaped molecule which has the two ends of the Y can recognise certain molecules that will be on the surface or a cell that might be floating around in the body. So if we attach these antibody Y-shaped molecules to the surface of the capsule, we’ve shown that they will then specifically stick to the cancer cells and go inside the cancer cells, rather than going to, for example, a healthy cell.

Then there's work that other people do where they take very small molecules, so things like folic acid. It’s known that on a lot of cancer cells they over-express a receptor for folic acid. So if you functionalise a capsule or a particle with folic acid you can get preferential uptake of these drugs to those cancer cells.

SHANE HUNTINGDON
I’m Shane Huntington. And my guests today are Associate Professor Eva Harth and Dr Angus Johnston. We’re talking about cancer therapy on the nanoscale here on Up Close, coming to you from the University of Melbourne, Australia.
Angus, there must be other things that you can do with these nanoparticles beyond the sorts of drugs that we’ve been talking about for cancer therapies. What other things are there that are being explored?


ANGUS JOHNSTON
The three main areas that our group works on in the cancer therapy, like we’ve been discussing. Then we’re also looking at vaccines. So there's a number of vaccines that are being developed that have shown a great deal of promise, particularly towards things like HIV. They show a significant amount of promise in in-vitro settings. So we do experiments in the lab and they look really good. But as soon as you put them into the body, the body is very well trained to recognise foreign material and it just destroys it as soon as you put it in there. So the hope is that by putting these very delicate vaccines inside a capsule and delivering it specifically to immune cells then we can sort of bypass the clearance mechanism, where the body gets rid of this foreign material, and we can elicit an immune response.
That’s one area. Then a somewhat related area, we sort of see the nanotechnology having two advantages. One is that you can protect the body from the side effects of the drug. So that’s what happens in cancer therapy. When you’ve got a very toxic drug, you want to limit its side effects. The other thing is, like I was saying with the vaccines, is that the body can also be very harmful to what you’re trying to deliver. So you want to protect it.
The other thing that people are interested in delivering is DNA and RNA because both of these materials are very easily degraded inside the body. If you can potentially encapsulate them inside a capsule - and even if it gets delivered to a number of cells. So you don’t necessarily have to be quite as targeted. But the fact that you’ve protected it from degradation and, if even a small percentage of it reaches the cells that you’re interested in, then you can potentially have improved gene therapy. So there was a recent example from a group in California who showed, for the first time, siRNA in a clinical trial was effective. SiRNA means short interfering RNA. What that can do is basically control cellular processes very exquisitely. So you can basically switch on or switch off expression of particular proteins. So, in the case of cancer cells where they’re growing uncontrollably, you can potentially switch off the thing that’s sort of gone wrong with those cells and basically correct them so they become more normal.

SHANE HUNTINGDON
Eva, can I ask you, with regards to this type of gene therapy, are you using your nanoparticles at this stage in that sort of area?

EVA HARTH
We have tried these particles only for small molecule therapy at the moment. We are very focused to try different cancers. So we have done a number of different mouse studies with breast, glioma and lung cancer. So we are very focused to try out different cancer drugs and also in combination. So this is our main focus. So we have started to work on gene therapy. But we thought that this is a very far reach for us and we wanted to look into chemotherapeutics which are already out there, which are very potent but not very much used.
So since the nanoparticle makes drugs more soluble, in most of the drugs they fail in the last step of the clinical trials because of toxicity and solubility issues. We think that also our nanoparticle might help drug discovery companies to develop better cancer therapeutics. Since we make them more soluble, so they would have been fallen through the drug discovery grid, they can be used in the body. So I’m saying that rather than making an assay in an organic solvent and then the drug looks very good but when you put it into the body and it becomes very insoluble then the entire work, the entire drug is not usable anymore. This would be prevented with the nanosponge. I think we can help also the industry with this nanosponge to make the drug discovery portfolio much broader, which is a huge issue.

SHANE HUNTINGDON
Presumably there are an entire range of drugs that have slipped through that stage in clinical trials, where they didn’t make it through to the body that your techniques may give advantage to. Can I ask you, are there side effects from the nanoparticles themselves when they’re used in this context?

EVA HARTH
No. We don’t think so. The polyester backbones, they are quite popular in the body already. So for example, for tissue engineering. So we have not used a very exotic particle. So the only difference is that the connectivity of the different linear parts, this is different and this is our unique technique that we built a sponge. But the network itself, it is biocompatible and we have done already toxicity testings which we have to do on a cellular level and also on the animal level. These particles look all fine in the amount you want to use them. The only toxic part is basically the drug molecule itself.

SHANE HUNTINGDON
Eva, let me ask you, with regards to something as specific as treating a pregnant woman without actually affecting the foetus that that woman is carrying, do the nanoparticles sort of present a possibility to do that? Because this has been one of the really big problems in dealing with a variety of diseases and concerns, even just simple cold medication. When people are pregnant, they’re unable to take many of these medications. How do the nanoparticles stack up with that?

EVA HARTH
We have not tested this of course. But I think here the targeting ability comes into place again. So you have to have a particle available which targets very quickly the cancer cell or the site of action. When the drug is protected and it cannot reach other organs where it should not go and cannot stay around for a long time to release the drug, I think this would be then also suitable for pregnant woman.
So since the targeting ability has to be very fast, the entire particle would not stay around for a long time or circulate in the body itself. So I think it would not accumulate in the heart or in the liver of a pregnant mother or in the baby, because this is the problem of all sustained release systems right now, that they collect in an organ and then they give the drug away in the wrong place, in a very critical place. I think, when you have a fast targeting ability, you can avoid all this.

SHANE HUNTINGDON
Eva Harth, Associate Professor of chemistry at Vanderbilt University, Nashville, Tennessee, and Dr Angus Johnston, Research Fellow at the Nanostructured Interfaces and Materials Group in the Department of Chemical and Biomolecular Engineering here at the University of Melbourne, Australia. Thank you for being our guests on Up Close today and giving us a much better understanding of cancer therapy at the nanoscale.

ANGUS JOHNSTON
Thanks very much.

EVA HARTH
Thank you so much for having me.

SHANE HUNTINGDON
Relevant links, a full transcript and more info on this episode can be found at our website at upclose.unimelb.edu.au. Up Close is a production of the University of Melbourne, Australia. This episode was recorded on 9 June, 2011. Our producers for this episode were Kelvin Param and Eric van Bemmel. Audio engineering by Gavin Nebauer. Background research by Dyani Lewis. Up Close was created by Eric van Bemmel and Kelvin Param. I’m Shane Huntington. Until next time, goodbye.

VOICEOVER
You’ve been listening to Up Close. For more information, visit upclose.unimelb.edu.au. Copyright 2011, the University of Melbourne.


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