Tag Archives: Cardiff University

Discovering why nanoscale gold has catalytic properties

Gold’s glitter may have inspired poets and triggered wars, but its catalytic prowess has helped make chemical reactions greener and more efficient. (Image courtesy of iStock/sbayram) [downloaded from http://www1.lehigh.edu/news/scientists-uncover-secret-gold%E2%80%99s-catalytic-powers

Gold’s glitter may have inspired poets and triggered wars, but its catalytic prowess has helped make chemical reactions greener and more efficient. (Image courtesy of iStock/sbayram) [downloaded from http://www1.lehigh.edu/news/scientists-uncover-secret-gold%E2%80%99s-catalytic-powers

A Sept. 27, 2016 news item on phys.org describes a discovery made by scientists at Lehigh University (US),

Settling a decades-long debate, new research conclusively shows that a hierarchy of active species exists in gold on iron oxide catalysis designed for low temperature carbon monoxide oxidation; Nanoparticles, sub-nanometer clusters and dispersed atoms—as well as how the material is prepared—are all important for determining catalytic activity.

A Sept. 27, 2016 Lehigh University news release by Lori Friedman, which originated the news item, provides more information about the discovery that gold nanoparticles can be used in catalysis and about the discovery of why that’s possible,

Christopher J. Kiely calls the 1982 discovery by Masatake Haruta that gold (Au) possessed a high level of catalytic activity for carbon monoxide (CO) oxidation when deposited on a metal-oxide “a remarkable turn of events in nanotechnology”—remarkable because gold had long been assumed to be inert for catalysis.

Haruta showed that gold dispersed on iron oxide effectively catalyzed the conversion of harmful carbon monoxide into more benign carbon dioxide (CO2) at room temperatures—a reaction that is critical for the construction of fire fighters’ breathing masks and for removal of CO from hydrogen feeds for fuel cells. In fact, today gold catalysts are being exploited in a major way for the greening of many important reactions in the chemical industry, because they can lead to cleaner, more efficient reactions with fewer by-products.

Haruta and Graham J. Hutchings, who co-discovered the use of gold as a catalyst for different reactions, are noted as Thompson Reuters Citation Laureates and appear annually on the ScienceWatch Nobel Prize prediction list. Their pioneering work opened up a new area of scientific inquiry and kicked off a decades-long debate about which type of supported gold species are most effective for the CO oxidation reaction.

In 2008, using electron microscopy technology that was not yet available in the 1980s and ’90 s, Hutchings, the director of the Cardiff Catalysis Institute at Cardiff University worked with Kiely, the Harold B. Chambers Senior Professor Materials Science and Engineering at Lehigh, examined the structure of supported gold at the nanoscale. One nanometer (nm) is equal to one one-billionth of a meter or about the diameter of five atoms.

Using what was then a rare piece of equipment—Lehigh’s aberration-corrected JEOL 2200 FS scanning transmission electron microscope (STEM)—the team identified the co-existence of three distinct gold species: facetted nanoparticles larger than one nanometer in size, sub-clusters containing less than 20 atoms and individual gold atoms strewn over the support. Because only the larger gold nanoparticles had previously been detected, this created debate as to which of these species were responsible for the good catalytic behavior.

Haruta, professor of applied chemistry at Tokyo Metropolitan University, Hutchings and Kiely have been working collaboratively on this problem over recent years and are now the first to demonstrate conclusively that it is not the particles or the individual atoms or the clusters which are solely responsible for the catalysis—but that they all contribute to different degrees. Their results have been published in an article in Nature Communications titled: “Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation.”

“All of the species tend to co-exist in conventionally prepared catalysts and show some level of activity,” says Kiely. “They all do something—but some less efficiently than others.”

Their research revealed the sub-nanometer clusters and 1-3nm nanoparticles to be the most efficient for catalyzing this CO oxidation reaction, while larger particles were less so and the atoms even less.  Nevertheless, Kiely cautions, all the species present need to be considered to fully explain the overall measured activity of the catalyst.

Among the team’s other key findings: the measured activity of gold on iron oxide catalysts is exquisitely dependent on exactly how the material is prepared. Very small changes in synthesis parameters  influence the relative proportion and spatial distribution of these various Au species on the support material and thus have a big impact on its overall catalytic performance.

A golden opportunity

Building on their earlier work (published in a 2008 Science article), the team sought to find a robust way to quantitatively analyze the relative population distributions of nanoparticles of various sizes, sub-nm clusters and highly dispersed atoms in a given gold on iron oxide sample. By correlating this information with catalytic performance measurements, they then hoped to determine which species distribution would be optimal to produce the most efficient catalyst, in order to utilize the precious gold component in the most cost effective way.

Ultimately, it was a catalyst synthesis problem the team faced that offered them a golden opportunity to do just that.

During the collaboration, Haruta’s and Hutchings’ teams each prepared gold on iron oxide samples in their home labs in Tokyo and Cardiff. Even though both groups nominally utilized the same ‘co-precipitation’ synthesis method, it turned out that a final heat treatment step was beneficial to the catalytic performance for one set of materials but detrimental to the other. This observation provided a fascinating scientific conundrum that detailed electron microscopy studies performed by Qian He, one of Kiely’s PhD students at the time, was key to solving. Qian He is now a University Research Fellow at Cardiff University leading their electron microscopy effort.

“In the end, there were subtle differences in the order and speed in which each group added in their ingredients while preparing the material,” explains He. “When examined under the electron microscope, it was clear that the two slightly different methods produced quite different distributions of particles, clusters and dispersed atoms on the support.”

“Very small variations in the preparation route or thermal history of the sample can alter the relative balance of supported gold nanoparticles-to-clusters-to-atoms in the material and this manifests itself in the measured catalytic activity,” adds Kiely.

The group was able to compare this set of materials and correlate the Au species distributions with catalytic performance measurements, ultimately identifying the species distribution that was associated with greater catalytic efficiency.

Now that the team has identified the catalytic activity hierarchy associated with these supported gold species, the next step, says Kiely, will be to modify the synthesis method to positively influence that distribution to optimize the catalyst performance while making the most efficient use of the precious gold metal content.

“As a next stage to this study we would like to be able to observe gold on iron oxide materials in-situ within the electron microscope while the reaction is happening,” says Kiely.

Once again, it is next generation microscopy facilities that may hold the key to fulfilling gold’s promise as a pivotal player in green technology.

Despite the link to the paper already in the news release, here’s one that includes a citation,

Identification of Active Gold Nanoclusters on Iron Oxide Supports for CO Oxidation by Andrew A. Herzing, Christopher J. Kiely, Albert F. Carley, Philip Landon, Graham J. Hutchings. Science  05 Sep 2008: Vol. 321, Issue 5894, pp. 1331-1335 DOI: 10.1126/science.1159639

This paper is currently behind a paywall but, if you can wait one year, free access can be gained if you register (for free) with Science.

Science literacy, science advice, the US Supreme Court, and Britain’s House of Commons

This ‘think’ piece is going to cover a fair bit of ground including science literacy in the general public and in the US Supreme Court, and what that might mean for science advice and UK Members of Parliament (MPs).

Science literacy generally and in the US Supreme Court

A science literacy report for the US National Academy of Sciences (NAS), due sometime from early to mid 2017, is being crafted with an eye to capturing a different perspective according to a March 24, 2016 University of Wisconsin-Madison news release by Terry Dewitt,

What does it mean to be science literate? How science literate is the American public? How do we stack up against other countries? What are the civic implications of a public with limited knowledge of science and how it works? How is science literacy measured?

These and other questions are under the microscope of a 12-member National Academy of Sciences (NAS) panel — including University of Wisconsin—Madison Life Sciences Communication Professor Dominique Brossard and School of Education Professor Noah Feinstein — charged with sorting through the existing data on American science and health literacy and exploring the association between knowledge of science and public perception of and support for science.

The committee — composed of educators, scientists, physicians and social scientists — will take a hard look at the existing data on the state of U.S. science literacy, the questions asked, and the methods used to measure what Americans know and don’t know about science and how that knowledge has changed over time. Critically for science, the panel will explore whether a lack of science literacy is associated with decreased public support for science or research.

Historically, policymakers and leaders in the scientific community have fretted over a perceived lack of knowledge among Americans about science and how it works. A prevailing fear is that an American public unequipped to come to terms with modern science will ultimately have serious economic, security and civic consequences, especially when it comes to addressing complex and nuanced issues like climate change, antibiotic resistance, emerging diseases, environment and energy choices.

While the prevailing wisdom, inspired by past studies, is that Americans don’t stack up well in terms of understanding science, Brossard is not so convinced. Much depends on what kinds of questions are asked, how they are asked, and how the data is analyzed.

It is very easy, she argues, to do bad social science and past studies may have measured the wrong things or otherwise created a perception about the state of U.S. science literacy that may or may not be true.

“How do you conceptualize scientific literacy? What do people need to know? Some argue that scientific literacy may be as simple as an understanding of how science works, the nature of science, [emphasis mine]” Brossard explains. “For others it may be a kind of ‘civic science literacy,’ where people have enough knowledge to be informed and make good decisions in a civics context.”

Science literacy may not be just for the public, it would seem that US Supreme Court judges may not have a basic understanding of how science works. David Bruggeman’s March 24, 2016 posting (on his Pasco Phronesis blog) describes a then current case before the Supreme Court (Justice Antonin Scalia has since died), Note: Links have been removed,

It’s a case concerning aspects of the University of Texas admissions process for undergraduates and the case is seen as a possible means of restricting race-based considerations for admission.  While I think the arguments in the case will likely revolve around factors far removed from science and or technology, there were comments raised by two Justices that struck a nerve with many scientists and engineers.

Both Justice Antonin Scalia and Chief Justice John Roberts raised questions about the validity of having diversity where science and scientists are concerned [emphasis mine].  Justice Scalia seemed to imply that diversity wasn’t esential for the University of Texas as most African-American scientists didn’t come from schools at the level of the University of Texas (considered the best university in Texas).  Chief Justice Roberts was a bit more plain about not understanding the benefits of diversity.  He stated, “What unique perspective does a black student bring to a class in physics?”

To that end, Dr. S. James Gates, theoretical physicist at the University of Maryland, and member of the President’s Council of Advisers on Science and Technology (and commercial actor) has an editorial in the March 25 [2016] issue of Science explaining that the value of having diversity in science does not accrue *just* to those who are underrepresented.

Dr. Gates relates his personal experience as a researcher and teacher of how people’s background inform their practice of science, and that two different people may use the same scientific method, but think about the problem differently.

I’m guessing that both Scalia and Roberts and possibly others believe that science is the discovery and accumulation of facts. In this worldview science facts such as gravity are waiting for discovery and formulation into a ‘law’. They do not recognize that most science is a collection of beliefs and may be influenced by personal beliefs. For example, we believe we’ve proved the existence of the Higgs boson but no one associated with the research has ever stated unequivocally that it exists.

For judges who are under the impression that scientific facts are out there somewhere waiting to be discovered diversity must seem irrelevant. It is not. Who you are affects the questions you ask and how you approach science. The easiest example is to look at how women were viewed when they were subjects in medical research. The fact that women’s physiology is significantly different (and not just in child-bearing ways) was never considered relevant when reporting results. Today, researchers consider not only gender, but age (to some extent), ethnicity, and more when examining results. It’s still not a perfect but it was a step forward.

So when Brossard included “… an understanding of how science works, the nature of science …” as an aspect of science literacy, the judges seemed to present a good example of how not understanding science can have a major impact on how others live.

I’d almost forgotten this science literacy piece as I’d started the draft some months ago but then I spotted a news item about a science advice/MP ‘dating’ service in the UK.

Science advice and UK MPs

First, the news, then, the speculation (from a June 6, 2016 news item on ScienceDaily),

MPs have expressed an overwhelming willingness to use a proposed new service to swiftly link them with academics in relevant areas to help ensure policy is based on the latest evidence.

A June 6, 2016 University of Exeter press release, which originated the news item, provides more detail about the proposed service and the research providing the supporting evidence (Note: A link has been removed),

The government is pursuing a drive towards evidence-based policy, yet policy makers still struggle to incorporate evidence into their decisions. One reason for this is limited easy access to the latest research findings or to academic experts who can respond to questions about evidence quickly.

Researchers at Cardiff University, the University of Exeter and University College London have today published results of the largest study to date reporting MPs’ attitudes to evidence in policy making and their reactions to a proposed Evidence Information Service (EIS) – a rapid match-making advisory service that would work alongside existing systems to put MPs in touch with relevant academic experts.

Dr Natalia Lawrence, of the University of Exeter, said: “It’s clear from our study that politicians want to ensure their decisions incorporate the most reliable evidence, but it can sometimes be very difficult for them to know how to access the latest research findings. This new matchmaking service could be a quick and easy way for them to seek advice from cutting-edge researchers and to check their understanding and facts. It could provide a useful complement to existing highly-valued information services.”

The research, published today in the journal Evidence and Policy, reports the findings of a national consultation exercise between politicians and the public. The researchers recruited members of the public to interview their local parliamentary representative. In total 86, politicians were contacted with 56 interviews completed. The MPs indicated an overwhelming willingness to use a service such as the EIS, with 85% supporting the idea, but noted a number of potential reservations related to the logistics of the EIS such as response time and familiarity with the service. Yet, the MPs indicated that their logistical reservations could be overcome by accessing the EIS via existing highly-valued parliamentary information services such as those provided by the House of Commons and Lords Libraries. Furthermore prior to rolling out the EIS on a nationwide basis it would first need to be piloted.

Developing the proposed EIS in line with feedback from this consultation of MPs would offer the potential to provide policy makers with rapid, reliable and confidential evidence from willing volunteers from the research community.

Professor Chris Chambers, of Cardiff University, said: “The government has given a robust steer that MPs need to link in more with academics to ensure decisions shaping the future of the country are evidence-based. It’s heartening to see that there is a will to adopt this system and we now need to move into a phase of developing a service that is both simple and effective to meet this need.”

The next steps for the project are parallel consultations of academics and members of the public and a pilot of the EIS, using funding from GW4 alliance of universities, made up of Bath, Bristol, Cardiff and Exeter.

What this study shows:
• The consultation shows that politicians recognise the importance of evidence-based policy making and agree on the need for an easier and more direct linkage between academic experts and policy makers.
• Politicians would welcome the creation of the EIS as a provider of rapid, reliable and confidential evidence.

What this study does not show:
• This study does not show how academics would provide evidence. This was a small-scale study which consulted politicians and has not attempted to give voice to the academic community.
• This study does not detail the mechanism of an operational EIS. Instead it indicates the need for a service such as the EIS and suggests ways in which the EIS can be operationalized.

Here’s a link to and a citation for the paper,

Service as a new platform for supporting evidence-based policy: a consultation of UK parliamentarians by Natalia Lawrence, Jemma Chambers, Sinead Morrison, Sven Bestmann, Gerard O’Grady, Christopher Chambers, Andrew Kythreotis. Evidence & Policy: A Journal of Research, Debate and Practice DOI: http://dx.doi.org/10.1332/174426416X14643531912169 Appeared or available online: June 6, 2016

This paper is behind a paywall open access. *Corrected June 17, 2016.*

It’s an interesting idea and I can understand the appeal. However, operationalizing this ‘dating’ or ‘matchmaking’ service could prove quite complex. I appreciate the logistics issues but I’m a little more concerned about the MPs’ science literacy. Are they going to be like the two US justices who believe that science is the pursuit of immutable facts? What happens if two MPs are matched up with a different scientist and those two scientists didn’t agree about what the evidence says. Or, what happens if one scientist is more cautious than the other. There are all kinds of pitfalls. I’m not arguing against the idea but it’s going to require a lot of careful consideration.

Nanodiamond alternative to organic fluorophores to view inside living human cells

No sooner is a Nobel prize (2014) awarded for nanoscopy which makes use of fluorescence to observe processes in living cells than there is an announcement about a new technique that avoids fluorescence and its attendant shortcomings. From an Oct. 27, 2014 news item on Nanowerk (Note: A link has been removed),

Nanodiamonds are providing scientists with new possibilities for accurate measurements of processes inside living cells with potential to improve drug delivery and cancer therapeutics.

Published in Nature Nanotechnology (“Coherent anti-Stokes Raman scattering microscopy of single nanodiamonds”), researchers from Cardiff University have unveiled a new method for viewing nanodiamonds inside human living cells for purposes of biomedical research.

An Oct. 27, 2014 Cardiff University (Wales) news release, which originated the news item, explains why the use of nanodiamonds is superior to the use of organic flurophores,

Nanodiamonds are very small particles (a thousand times smaller than human hair) and because of their low toxicity they can be used as a carrier to transport drugs inside cells. They also show huge promise as an alternative to the organic fluorophores usually used by scientists to visualise processes inside cells and tissues.

A major limitation of organic fluorophores is that they have the tendency to degrade and bleach over time under light illumination. This makes it difficult to use them for accurate measurements of cellular processes. Moreover, the bleaching and chemical degradation can often be toxic and significantly perturb or even kill cells.

There is a growing consensus among scientists that nanodiamonds are one of the best inorganic material alternatives for use in biomedical research, because of their compatibility with human cells, and due to their stable structural and chemical properties.

Previous attempts by other research teams to visualise nanodiamonds under powerful light microscopes have run into the obstacle that the diamond material per se is transparent to visible light. Locating the nanodiamonds under a microscope had relied on tiny defects in the crystal lattice, which fluoresce under light illumination.

Production of the defects proved both costly and difficult to realise in a controlled way. Furthermore, the fluorescence light emitted by these defects, and in turn the image gleaned from the microscopic exploration of these flawed nanodiamonds, is sometimes also unstable.

In their latest paper, researchers from Cardiff University’s Schools of Biosciences and Physics showed that non-fluorescing nanodiamonds (diamonds without defects) can be imaged optically and far more stably via the interaction between the illuminating light and the vibrating chemical bonds in the diamond lattice structure which results in scattered light at a different colour.

The paper describes how two laser beams beating at a specific frequency are used to drive chemical bonds to vibrate in sync. One of these beams is then used to probe this vibration and generate a light, called coherent anti-Stokes Raman scattering (CARS).

By focusing these laser beams onto the nanodiamond, a high-resolution CARS image is generated. Using an in-house built microscope, the research team was able to measure the intensity of the CARS light on a series of single nanodiamonds of different sizes.

The nanodiamond size was accurately measured by means of electron microscopy and other quantitative optical contrast methods developed within the researcher’s lab. In this way, they were able to quantify the relationship between the CARS light intensity and the nanoparticle size.

Consequently, the calibrated CARS signal enabled the team to analyse the size and number of nanodiamonds that had been delivered into living cells, with a level of accuracy hitherto not achieved by other methods.

Professor Paola Borri from the School of Biosciences, who led the study, said: “This new imaging modality opens the exciting prospect of following complex cellular trafficking pathways quantitatively with important applications in drug delivery. The next step for us will be to push the technique to detect nanodiamonds of even smaller sizes than what we have shown so far and to demonstrate a specific application in drug delivery.”

Here’s a link to and a citation for the paper,

Coherent anti-Stokes Raman scattering microscopy of single nanodiamonds by Iestyn Pope, Lukas Payne, George Zoriniants, Evan Thomas, Oliver Williams, Peter Watson, Wolfgang Langbein, & Paola Borri. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.210 Published online 12 October 2014

The paper is behind a paywall but there is a free preview with ReadCube Access.

For anyone who’d like to read more about fluorescence and its use in nanoscopy there’s my Oct. 8, 2014 posting about the 2014 Nobel Prize in Chemistry and in my Oct. 27, 2014 posting about a specific use for determining how bipolar disorder may affect the brain.

Toxicity, nanoparticles, soil, and Europe’s NANO-ECOTOXICITY Project

I have featured pieces on nanoparticles, toxicity, and soil in the past (this Aug. 15, 2011 posting about Duke University’s mesocosm project is probably the most relevant) but this study is the first one I’ve seen focusing on earthworms. From the Sept. 23, 2013 news item on Nanowerk (Note: A link has been removed),

From the clothes and make-up we wear to the electronic devices we use every day, nanotechnology is becoming ubiquitous. But while industry has mastered the production of such materials, little is known about their fate once their service life comes to an end. The NANO-ECOTOXICITY project looked into their impact on soil organisms.

The Sept. 23, 2013 CORDIS (European Commission Community Research and Development Information Service) news release, which originated the new item, offers a Q&A (Question and Answer) with the project research leader,

Dr Maria Diez-Ortiz, research leader of the NANO-ECOTOXICITY project, tells us about her research findings and how she expects them to help increase knowledge and shape tools allowing for standard environmental hazard and risk-assessment methodologies.

What is the background of the NANO-ECOTOXICITY project?

Nanotechnology is based on the idea that, by engineering the size and shape of materials at the scale of atoms, i.e. nanometres (nm), distinct optical, electronic, or magnetic properties can be tuned to produce novel properties of commercial value. However, there is an obvious concern that such novel properties may also lead to novel behaviour when interacting with biological organisms, and thus to potentially novel toxic effects.

Since nanoparticles (NPs) are similar in size to viruses, their uptake by and transport through tissues are based on mechanisms distinct from those of molecular uptake and transport. Therefore, there is concern that standard toxicological tests may not be applicable or reliable in relation to NPs, hence compromising current risk-assessment procedures.

The majority of research on nano-safety in the environment has so far focused on the aquatic environment. Current research on environmental fate, however, indicates that soils will become the biggest environmental sink for nanoparticles. Following their entry into liquid waste streams, nanoparticles will pass through wastewater-treatment. processes, ending up in waste sludge which may accumulate in the agricultural land where this sludge is often applied.

What are the main objectives of the project?

This project deals with the toxicokinetics – that is, the rate at which a chemical enters a body and affects it – of metal nanoparticles coming into contact with soil-dwelling organisms. The aim is to determine NPs’ fate and effects in terrestrial ecosystems by means of case studies with zinc oxide and silver NPs, which represent different fate kinetics.

The project’s main objectives are to assess the toxicity of metal nanoparticles in soils in the short and long term; the main route of exposure for earthworms and whether it differs from those of ionic metals; and, finally, the influence of the exposure media on metal nanoparticle toxicity.

What is new or innovative about the project and the way it is addressing these issues?

We have been running a long-term study where soils with AgNP [silver nanoparticles] were stored and left to age for up to a year; their toxicity was tested at the start and after three, seven and 12 months of ageing. The results showed that silver toxicity increased over time, meaning that short-term standard toxicity tests may underestimate the environmental risk of silver nanoparticles.

In parallel, we found that organisms exposed to silver nanoparticles in short-term studies accumulated higher silver concentrations than organisms that were exposed to the same mass concentration of ionic silver. However, these NP exposed organisms actually suffered lower toxic effects. This observation contradicts the prevailing assumption in toxicology that the internalised concentration is directly related to chemical concentration at the target site and hence to its toxicity. This observation creates a new paradigm for nano-ecotoxicology.

What is not yet known is whether the accumulated NP metal may in the longer-term ultimately become toxic (e.g. through dissolution and ion release) in cells and tissues where AgNPs may be stored. Should this occur, the high concentrations accumulated may ultimately result in greater long-term toxicity for NPs than for ionic forms. This may reveal these accumulated NPs as internalised ‘time bombs’ relevant to long-term effects and toxicity.

However, it has to be borne in mind that the redicted environmental concentrations resulting from current use of nanoparticles (e.g. results from EU projects like NANOFATE2) are many times smaller than those used in these studies, meaning that such accumulations of nanoparticle-related silver are unlikely to occur in the environment or, ultimately, in humans.

What difficulties did you encounter and how did you solve them?

The main problems encountered relate to the tracking of nanoparticles inside the tissues and soils, as both are complex matrices. The analysis of the particles is a challenge in itself, even when in water, but to get information about their state in these matrices often requires unrealistic exposure concentrations (due to low detection limits of the highly specialised techniques used for analysis) or extraction of the particles from the matrices, which could potentially change the state of the particles.

In this project, I travelled to University of Kentucky to work with Jason Unrine and used gentle water-based extractions of soil samples immediately before analysing them using ‘Field-flow fractionation’ and ‘Inductively coupled plasma mass spectrometry’ to identify the state of nanoparticles in my aged soils.

To look at what form (speciation) of silver and zinc from the nanoparticle exposures could be found inside worms I collaborated with NANOFATE researchers at Cardiff University who fixed and thinly sectioned the worm tissues. I was lucky to be given the time to use specialist facilities like the UK’s Diamond Light Source synchrotron to investigate where and in what form the metals and potential nanoparticles could be found in these tissues.

The main challenge is that as soon as you take nanoparticles out of the manufacturers’ bottle they start changing, particularly when put into environments likes natural soils and waters, or even organisms. Therefore a lot of characterisation is needed during exposure to establish the state of the nanoparticles the organisms have been exposed to and how fast they are changing from pristine particles to dissolved ions, or particles with completely different surfaces.

Technical solutions to characterisation have been found during this short project, but this will remain a logistical challenge for many years to come as the analysis equipment is still very specialised and expensive and therefore not generally available.

What are the concrete results from the research so far?

The project has helped us draw various conclusions regarding the impact of NPs on the environment and how to assess them. First, we now know that soil acidity, or pH, influences the dissolution and toxicity of ZnO nanoparticles [zinc oxide].

Then, we found that toxicity of silver nanoparticles’ increases over time and that the particles’ coating affects their toxicity to soil invertebrates.

As previously mentioned, earthworms exposed to silver nanoparticles for 28 days accumulated higher silver concentrations than earthworms exposed to silver ions, without the excess silver from the nanoparticles having a toxic effect. [emphasis mine] Moreover, soil ingestion was identified as the main route of exposure to AgNP and ZnONP in earthworms.

How can industry and decision-makers ensure that nanomaterials do not impact our environment?

We hope that this project, and the larger EU project NANOFATE to which it is linked, will provide knowledge and tools enabling standard environmental-hazard and risk-assessment methodologies to be applied to engineered nanoparticles (ENPs) with just a few judicious modifications. The current systems and protocols for chemical risk assessment have been developed over decades, and where no novel toxic mechanisms exist, our results tend to say that nano fits in as long as we measure the right things and characterise realistic exposures properly.

Our research aims to determine the minimum methodological tweaks needed. So far everything indicates that the potential benefits from nanotechnology can be realised and managed safely alongside other chemicals. While we are fairly confident at this stage that ENPs impose no greater acute effects on important biological parameters – like reproduction – than their ionic forms, the NANO-ECOTOXICITY results demonstrate that we have some way to go before we can state loud and clear that we do not believe there is any novel low-level or long-term effect.

As for all chemicals, proving such a negative is impossible using short-term tests. We think the final conclusions by industry and regulators on safe use of nanoparticles should and will have to be made according to a ‘weight of evidence’ approach – proving there is a gap between predicted likely exposure levels and those levels seen to cause any effects or accumulations within ecosystem species.

What are the next topics for your research?

This project has finished but the next step for any other funding opportunity would be to address increasingly environmentally relevant exposure scenarios by analysing how nanoparticles modify in the environment and interact with living tissues and organisms at different trophic levels. I would like to investigate nanoparticle transformation and interactions in living tissues. To date, the studies that have identified this ‘excess’ accumulation of non-toxic metal loads in nanoparticleexposed organisms have only been short term.

Apart from the obviously increased food-chain transfer potential, is also not known whether, over the longer term, the accumulated NP-derived metal ultimately becomes toxic when present in tissues and cells. Such transformation and release of metal ions within tissues may ultimately result in greater longterm toxicity for NPs than for ionic forms.

Furthermore, I want to test exposures in a functioning model ecosystem including interspecific interactions and trophic transfer. Since interactions between biota and nanoparticles are relevant in natural soil systems, caution is needed when attempting to predict the ecological consequences of nanoparticles based on laboratory assays conducted with only a single species. In the presence of the full complement of biological components of soil systems, complex NPs may follow a range of pathways in which coatings may be removed and replaced with exudate materials. Studies to quantify the nature of these interactions are therefore needed to identify the fate, bioavailability and toxicity of realistic ‘non-pristine’ forms of NPs present in real soil environments.

New to me was the material about ageing silver nanoparticles and their increased toxicity over time. While this is an interesting piece of information it’s not necessarily all that useful. It seems even with their increased uptake compared to silver ions, silver nanoparticles (Diez-Ortiz doesn’t indicate whether or not * they tested variously aged silver nanoparticles) did not have toxic effects on the earthworms tested.

The NANO-ECOTOXICITY website doesn’t appear to exist anymore but you can find the NANOFATE (Nanoparticle Fate Assessment and Toxicity in the Environment) website here.

* ‘not’ removed to clarify meaning, Oct. 9, 2013. (Note: I had on Oct. 8, 2013 removed ‘not’ in a second place from the sentence in an attempt t o clarify the meaning and ended up not making any sense at all.) Please read Maria Diez-Ortiz in the Comments, as she clarifies matters in a way I could never hope to.

Norwegians weigh in with research into wood nanocellulose healing application

It’s not just the Norwegians but they certainly seem to be leading the way on the NanoHeal project. Here’s a little more about the intricacies of healing wounds and why wood nanocellulose is being considered for wound healing, from the Aug. 23, 2012 news item on Nanowerk,

Wound healing is a complicated process consisting of several different phases and a delicate interaction between different kinds of cells, signal factors and connective tissue substance. If the wound healing does not function optimally, this can result in chronic wounds, cicatrisation or contractures. By having an optimal wound dressing such negative effects can be reduced. A modern wound dressing should be able to provide a barrier against infection, control fluid loss, reduce the pain during the treatment, create and maintain a moist environment in the wound, enable introduction of medicines into the wound, be able to absorb exudates during the inflammatory phase, have high mechanical strength, elasticity and conformability and allow for easy and painless release from the wound after use.

Nanocellulose is a highly fibrillated material, composed of nanofibrils with diameters in the nanometer scale (< 100 nm), with high aspect ratio and high specific surface area (“Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fibre technology point of view” [open access article in Nanoscale Research Letters]). Cellulose nanofibrils have many advantageous properties, such as high strength and ability to self-assembly.

Recently, the suitability of cellulose nanofibrils from wood for forming elastic cryo-gels has been demonstrated by scientists from Paper and Fibre Research Institute (PFI) and Lund University (“Cross-linking cellulose nanofibrils for potential elastic cryo-structured gels”  [open access in Nanoscale Research Letters). Cryogelation is a technique that makes it possible to engineer 3-D structures with controlled porosity. A porous structure with interconnected pores is essential for use in modern wound healing in which absorption of exudates, release of medicines into the wound or exchange of cells are essential properties.

The Research Council of Norway recently awarded a grant to the NanoHeal project, from the project page on the PFI (Pulp and Fibre Research Institute) website,

This multi-disciplinary research programme will develop novel material solutions for use in advanced wound healing based on nanofibrillated cellulose structures. This proposal requires knowledge on the effective production and application of sustainable and innovative micro- and nanofibres based on cellulose. The project will assess the ability of these nanofibres to interact with complementary polymers to form novel material structures with optimised adhesion and moulding properties, absorbance, porosity and mechanical performance.  The NanoHeal proposal brings together leading scientists in the fields of nanocellulose technology, polymer chemistry, printing and nanomedicine, to produce biocompatible and biodegradable natural polymers that can be functionalized for clinical applications. As a prototype model, the project will develop materials for use in wound healing. However, the envisaged technologies of synthesis and functionalization will have a diversity of commercial and industrial applications.

The project is funded by the Research Council of Norway/NANO2021, and is a cooperation between several leading R&D partners.

  • PFI
  • NTNU [Norwegian University of Science and Technology], Faculty of medicine
  • Cardiff University
  • Swansea University
  • Lund University
  • AlgiPharma

Project period: 2012-2016

I wonder when I’m going to start hearing about Canadian research into wood nanocellulose  (nanocrystalline cellulose or otherwise) applications.