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BioAFM Testimonials*
WALK LIKE A MYOSIN Toshio Ando
LOOK OUT, YOUTUBE Thomas Gutsmann
FOLLOW THE LEADER Paul Hansma
COLLABORATION: YOUR PLACE OR MINE? Michael Horton
THAT'S A BIG ADVANTAGE Lewis Francis
POWERFUL TECHNIQUE Liz Adams
THE CHALLENGE IS TO MAKE IT EASIER Daniel Navajas
SCALE NANO, UNIVERSE LARGE Pierre Parot
OPTIMISTIC ABOUT NEW DEVELOPMENTS Simon Scheuring
WALK LIKE A MYOSIN
Audible gasps went up throughout the audience as Toshio Ando of Kanazawa University in Japan showed a video. "You can see molecules moving," said Simon Scheuring afterwards. "I mean, would anyone have ever expected to see how myosins walk -- an individual myosin molecule walking along an actin filament? Just a few years ago, everyone would have said you're crazy. This is really one of the breakthroughs." Dr. Scheuring chaired the session on high-resolution imaging during which Professor Ando showed his images of the "walking" myosin.
But as Pierre Bongrand (INSERM, Marseille, France) said during his opening address to the conference, seeing is not enough -- we want dynamic interactions. Myosin, as Toshio Ando showed in his high-speed AFM video, is certainly dynamic. "Motor proteins are very interesting because they produce force and they move," Professor Ando said after his presentation. "They are involved in energy conversion. However, these dynamic functions were difficult to study because we had no appropriate tool. Now with AFM you have a tool for studying the dynamics of proteins.
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LOOK OUT, YOUTUBE
Thomas Gutsmann also presented sepsis-related research at the conference. In his work in the Division of Biophysics of the Research Center Borstel in Germany, Dr. Gutsmann investigates lung diseases. He uses AFM to study the interaction of antimicrobial agents with bacterial membranes, and to study the proteins involved in the signal transduction pathway of the immune system as it recognizes bacterial lipopolysaccharides. What does he see as the advantages of using AFM for his work compared to other types of microscopy? Dr. Gutsmann: "We use AFM to get a really high resolution, higher than with optical microscopy, and we can do the experiments in buffer. With electron microscopy you always have to fix the cells to do the experiment or image them in vacuum. With AFM, we can do the experiment in buffer, in different conditions, and this is closer to a natural system." In terms of new developments in AFM that he is interested in following and possibly using, Dr. Gutsmann mentioned several: reconstituted membranes applied to whole-cell functions, specific recognition of proteins on cells, the parallel use of more than one cantilever
functionalized for different antibodies, and high-speed AFM. "Most biological systems are dynamic, and AFM helps us understand the dynamics of the system," he said.
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FOLLOW THE LEADER
One of the early adopters, or, as Binnig4 put it in his Nobel lecture, "believers", in the use of this new technology was Paul Hansma of the University of California at Santa Barbara, USA. Professor Hansma went on to become an important innovator in several aspects of AFM development. He gave the keynote address at the AFM BioMed conference in Barcelona and his presence, along with several other pioneers in the use of AFM in life sciences research, was a big drawing factor for the conference.
Paul Hansma looked ahead towards clinical applications. "Back when we were developing AFM for biological applications, we were hoping that AFM would one day contribute to quality of life, like the light microscope and the electron microscope have in the past," he said. "I look forward to the day when you will send me the picture of the first person who was healed because of the use of an AFM."
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COLLABORATION: YOUR PLACE OR MINE?
During his closing address at the conference, Michael Horton, Life Sciences Director at the London Centre for Nanotechnology and Director of the Bone and Mineral Centre at University College London, emphasized the need for setting up cross-disciplinary collaboration up front rather than as an afterthought. The methods developed by physicists using AFM have filtered through to cell and molecular biology research by way of the biophysicists. But now that AFM has a relatively firm footing in the life sciences, biologists are becoming innovators in the use and applications of AFM as much as physicists have been. (See Table 2: AFM in biology research: benefits, limitations, and new developments.) The next step, according to Professor Horton, is to connect nanoscale research to clear biomedical needs.
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THAT'S A BIG ADVANTAGE
Lewis Francis is looking forward to using his lab's new combination AFM and confocal laser scanning microscope. "We've developed some confocal experiments and AFM experiments separately. The big thing now for us is the combined system," he said. As a PhD student at the Multidisciplinary Nanotechnology Centre and the Medical School at Swansea University in Wales, UK, Mr. Francis is studying the surface of the endometrium, the lining of the uterine wall, which is a key interface in reproductive biology. By studying and characterizing endometrial cells, he aims to contribute to a better understanding of female infertility and uterine cancer. He presented a poster at the conference with some of his AFM images obtained so far. As for the next steps in his work, he said: "We know that there is differential expression of MUC1 [a transmembrane glycoprotein that has anti-adhesive effects] across the endometrial cell surface -- we hope to be able to tie that in with the differential adhesion we see across the cell. The combined confocal-AFM technique will allow us to do that in one system and get one set of force curves all in one cell. That's a big advantage."
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POWERFUL TECHNIQUE also uses a combination of optical and atomic force microscopy in her research at the Delaware Biotechnology Institute, University of Delaware, USA. "AFM is a really powerful technique, as it is able to complement data generated from a range of different methods, which helps us learn a more complete story, not just from one angle," she said. "At the Bioimaging Center we cover everything from chemical engineering to biological sciences. In my own research, we're interested in looking at immunological cells and how they respond to different stimuli. For example, by using a fluorescent probe with the confocal microscope, it's possible to locate specific molecules. By combining the AFM, we are then able to relate this to topography, which makes it possible to see how these structures are interrelated and how they change over time. That's why we are moving toward combining these techniques." Dr. Adams presented research at the conference that looked at one particular ligand-receptor interaction that occurs during the innate immune response to fungal pathogens. Using AFM and confocal laser scanning microscopy, she was able to follow the binding of glucan (a polysaccharide found in fungal cell walls) to Dectin-expressing cells (Dectin is a glucan receptor found on some types of leukocytes), and show that this binding was selective and specific. What does this mean? Dr. Adams: "We've looked at these cells highly expressing a protein that's important to an innate immune response, so that we can begin to understand why the innate immune response doesn't seem to be able to protect certain people from really catastrophic diseases." While a possible clinical application is probably a stage that's far into the future, Dr. Adams sees value in studying this process at the molecular level. "I expect we'll see clinical applications once we understand the specifics of the interactions in more detail," she said. "Then we will have a better understanding of how to block or mediate these events"
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THE CHALLENGE IS TO MAKE IT EASIER
Daniel Navajas is a pioneer in using AFM to measure cell mechanical properties. He was also on the conference organizing committee, and is Head of Biophysics and Bioengineering at the University of Barcelona, Spain. (That Barcelona is home to a vibrant biotechnology sector, including several groups at the Bioengineering Institute of Catalonia who use AFM for biomedical applications, meshes nicely with the choice of the city as the location for the conference.) "I think an important step forward has been to combine AFM with other imaging techniques," said Professor Navajas when asked about AFM innovations. "It's also very important to use AFM in biology not just for imaging but also for manipulating -- cells and molecules and so on. This kind of work has already begun, but the challenge is to make it easier." This applies not only for AFM as used in research settings, but also for potential clinical applications in the future. "Using AFM for screening or diagnosis is very complex, because you have to measure cell by cell. One idea would be to place the cells on the cantilever automatically and to be able to measure thousands of cells in a minute. This could improve the facility of the technique for the clinical world," Professor Navajas said.
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SCALE NANO, UNIVERSE LARGE
That the response to the conference announcement in late 2006 would be so enthusiastic surprised the conference organizers. Pierre Parot and Jean-Luc Pellequer of the Life Sciences Division of the Atomic Energy Commission (CEA) in France and Daniel Navajas of the University of Barcelona, Spain were the key drivers on the scientific organizing committee. "During previous meetings on AFM research, we heard our colleagues say that this was all very interesting, but the focus was too much on physics, not enough on biology or medicine," Professor Parot said. "Something like 20% of all AFM publications are in the biomedical sciences, which is a very important sign. Two years ago we organized a small meeting in Nimes, France, with only 20 or 30 people. That was the first meeting to focus on AFM in biology. Then we decided to organize another one, a bigger one, but we really wondered how much interest there would be. We thought that if we could get 50 people to attend, that would be a big success. But after the first call for papers, we obtained more than 200 abstracts."
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OPTIMISTIC ABOUT NEW DEVELOPMENTS
Simon Scheuring is also optimistic about new developments in AFM. "One thing that is being developed is the combination of AFM with measuring secondary signals. In the field of my interest, membrane proteins, you can start seeing the real membranes, the native assemblies. This is very important," he said. "Visualizing motors is also important. Biological machines work at a much higher efficiency than whatever machines humans have created so far. The field of AFM as a force measurement tool will also develop. I cannot speculate about new inventions but these are some of the directions." There is also clinical potential ahead. "We are trying to develop AFM towards a technique that can be used for medical imaging," said Dr. Scheuring. "So far, the classical imaging techniques in medicine are relatively low-resolution techniques. Sometimes electron microscopy or immunostaining is used, but otherwise it's all cellular or tissue. Since we now understand that many diseases are due to molecular disorders, we have an interest in seeing the molecule."
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* Source: A Little Can Go A Long Way -- Fast
Impressions of the International Meeting on AFM in Biology and Medicine (AFM BioMed), Barcelona, 19-21 April 2007
Author: Shazia Qureshi, Freelance medical writer, Amsterdam, the Netherlands Email: qureshi.shazia@gmail.com