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Nano-sized gold particles fascinate newly appointed Academy Professor

Nano-sized gold particles fascinate newly appointed Academy Professor

Maria Virkkula

After finishing his PhD, Hannu Häkkinen faced a choice: teaching or research. He chose research. He is now an internationally recognised name with a litany of titles: Professor in Computational Science at the University of Jyväskylä, Scientific Director of the JYU Nanoscience Center and, as of January 2016, Academy Professor.

– It's a highly contested position in Finland, and many excellent researchers will never reach it. It's a gold medal of sorts.

– But it does raise people's expectations of you a notch. Now I'm expected to publish my research only in the very best and most competitive journals, says Häkkinen.

However, he's currently well poised to do so. He engages in pioneering basic research that combines chemistry and physics. His collaboration network consists of leading foreign research teams that include big names such as Roger D. Kornberg from Stanford University, winner of the Nobel Prize in Chemistry, and Hans-Joachim Freund, Director of the Fritz-Haber Institute in Germany.

Every year, he racks up a total of almost three months in business trips that take him all across the globe: America, China, Japan, India.

– Naturally you get bored sometimes, and airports and hotels are so mind-numbing. But this is interesting work, so I can't complain.

 

 

A nanometre of gold or silver

Häkkinen's research subjects are so small that it's difficult to get a handle on them. Metal particles measure about 1–3 nanometres, that is, only a millionth of a millimetre.

Häkkinen is interested in how we can better understand and harness nano-sized metal particles that are protected by organic molecules.

The research project for his Academy Professorship has been described as both innovative and ambitious. It focuses on a variety of nano structures and using the data obtained from them to support research into biological processes.

– The particles contain metal that could be gold or silver. They have a covering of organic molecules on their surface. Chemical treatments can be used to make them interact with, for example, virus proteins.

– No one has conducted this type of research before, not in Finland or anywhere else, says Häkkinen.
 

Interest first awakened back in the 90s

We've known about the synthesis that occurs in gold particles since the mid-1990s. However, it was only in 2007 that a team led by Nobel prizewinner Roger D. Kornberg, one of Häkkinen's current collaborators, determined the atomic structure of an individual particle.

This spurred Häkkinen's interest in gold particles, which had first awakened during the 90s. The first task was to analyse the structure of the particles and use simulations to try to explain why a particular particle was chemically stable.

With the aid of Finnish, German and Swedish high-performance computing resources, the answer was found in only a few weeks during autumn 2007, and the results were published with Kornberg's team in summer 2008.

– That's where it all started – and we expected it to become a significant field of research. We were able to alter the surface structure of metal particles using computational methods, and work out how to make the particles react with their surroundings.
 

Creating virus markers

Gold particles were first used in virus research in autumn 2011. Häkkinen happened to read an American article about gold particles that had been attached to a Tobacco Mosaic virus. He wondered whether gold particles could be used to benefit the structural study of viruses.

– The article contained images of gold particles on the surface of a virus, taken with an electron microscope. I thought that, if they were that visible, they could also be used for other things. The previous year, my chemistry colleagues Tanja Lahtinen, Maija Nissinen and Mika Pettersson had begun to synthesise and characterise gold particles at the Nanoscience Center. I thought we could try attaching them to viruses as well.

Häkkinen approached a former colleague, cell biologist Varpu Marjomäki. They immediately started working together and a report of their new imaging method was issued in January 2014.

– We were able to show that gold particles can be used as markers in the imaging of live viruses.

Markers consisting of nano-sized gold particles, which are even smaller than the microscopic viruses they are attached to, are used to provide more detailed information about the viruses' behaviour. The goal is to obtain images of the viruses when they begin to open.

– We know very little about viral cell lysis mechanisms. Our research – a combination of empirical experiments and simulations – will hopefully generate useful new data that can be used in, for example, the advancement of viral medicine.

Every year, enteroviruses cause a significant number of different infections, such as the commonplace flu. When a virus manages to infect a healthy cell, it opens and begins to replicate itself within the cell. These copies can then infect other cells.

– If we can understand these mechanisms properly, we'll be able to fight them.

Nuclear magnetic resonance spectrum of an Au102 nanoparticle measured in water (left). The spectrum was interpreted with the aid of the particle's known crystalline structure (right) and computational simulations. IMAGES: UNIVERSITY OF JYVÄSKYLÄ

 

"A major leap forward"

Less than a month into the newly appointed Academy Professor's term, he and his research team were already racking up international recognition.

The results of nanoparticle research conducted by Häkkinen's team and researchers from Colorado State University were published in the journal Nature Communications at the end of January. The researchers managed to obtain new data about the surface structure of gold particles (Au102) in water.

Understanding the structure and dynamics of the layer of organic molecules that protects nanometre-sized gold particles may be of significant benefit in the development of new applications – for example, in catalysis or as pharmaceutical transporters, molecular electronic components, or biocompatible markers.

– Now that we have a detailed understanding of how the molecule layer protecting an Au102 particle behaves in water, we also have a much better idea of how the particle interacts with, for example, biological materials. This is a major leap forward in our research, says Häkkinen.

 

 

Science around the clock

Häkkinen is a birdwatcher, and also likes to head into nature in his free time. However, work keeps him busy. Emails can arrive around the clock, as he's engaged in discussion with researchers all across the world.

– I want to keep doing research for as long as I can, Häkkinen says.

And not without good reason. Häkkinen believes that significant discoveries can be made in nanoscience, and that new applications will be found for nanoparticles.

Above all, Häkkinen seeks to shed more light on the structure of metallic nanoparticles.

– My research has already been making 'discoveries' and providing explanations for many years. But it won't be geared towards commercial applications. I want to generate hopefully useful data for engineers, so that they will know what they can do with metallic nanoparticles.

In other words, Häkkinen wants to continue with cutting-edge basic research. And a multidisciplinary cluster like the JYU Nanoscience Center, which Häkkinen is Scientific Director of, will provide excellent resources for this.

– It's been very important. We've learnt to discuss and cooperate. You can learn things from colleagues outside your field, and conduct more efficient research. It's fun to do research in the kind of inspiring atmosphere we have here at the Centre.

Häkkinen had this to say in a ten-year history of JYU Nanoscience Center published in 2014:

"In ten years' time, Jyväskylä will be home to the Finnish Academy's top nanoscience unit, which will hopefully have been up and running for several years. It will be engaging in globally unique and influential multidisciplinary research, and training talented researchers that can collaborate on multidisciplinary projects."  

– My dream is the same as it ever was, says Häkkinen.
 

 

Computational methods on the trail of gold nanoparticle structures

Hannu Häkkinen, Professor of Computational Science, is one of CSC's biggest and longest-term customers. He's been conducting computational research using CSC's supercomputers since the turn of the 1980s–90s.
– I simulated demanding numerical calculations for my doctoral thesis back in the late 80s. I knew there was an IT centre in Espoo that had more powerful computers than we had in Jyväskylä.
Since then, he's become very familiar with CSC's computers.
– I clearly remember using CSC's first Cray (supercomputer). It was an enormous step up from the computers we had in the Jyväskylä physics department. No leap since then has felt that large.
– I calculated thermal expansion curves. It was an x-y graph that showed metal density at various temperatures one point at a time. Espoo was sending data for the graph faster than I was able to manually edit the graph, Häkkinen recalls.

Since then he has taken advantage of CSC's resources in many research projects to run simulations relating to gold nanoparticles and other nano structures.
– It's important to conduct computational studies of particles in collaboration with empiricists. Usually, we no longer need to guess at the atomic structure of particles – we obtain the data from experiments and can then focus on determining their physical and chemical properties.
This requires enormous computing power. Häkkinen estimates that he needs about 100 million core hours for his Academy Professor project. This is a considerable amount. He will need to complement CSC's resources with international ones.
– CSC will play a vital role in that respect too, both now and in the future.

CSC's resources will ensure that researchers will also have access to computing resources and services provided by other European supercomputers.
However, Häkkinen doesn't think that research could be conducted to current standards without domestic resources and the competence of CSC's, now familiar, Finnish experts.
– It's decisive. There's no way I would have achieved so much without these resources.

Häkkinen thinks that Finland should maintain a high standard of expertise in high-performance computing.
– It's invaluable. Finland has been at the forefront of high-performance computing for years. If we don't stay there, other countries will overtake us in research. This is a competition – the kind in which equipment makes a difference.
– And I don't mean just speed or scalability, but rather infrastructure for high-performance computing. This will ensure that both top research and top researchers will remain in Finland.
– I've always seen CSC's cutting-edge research as an enabler, and I hope that it will remain so, says Häkkinen.

 



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