February | février 2011 • Vol.63, No./no 2
Canadian Chemical News | L’Actualité chimique canadienne A Magazine of the Chemical Institute of Canada and its Constituent Societies | Une magazine de l’institut de chimie du canada et ses sociétés constituantes
Re-imagining the Periodic Table Making More from MAPLE
Ti
V
Cr Mn Fe Co Ni
High Hopes for Hydrogels
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Chemical
Canadian Society for Chemistry
Call for Papers Opens December 1, 2010 • Closes February 15, 2011
Chemistry and Health 94th Canadian Chemistry Conference and Exhibition Montréal, Que., Canada
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CSC
Société canadienne de chimie
Demande de communications Débute le 1er décembre 2010 • Se termine le 15 février 2011
La chimie en santé
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du 5 au 9 juin 2011 www.csc2011.ca
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Contents
Features
12
Should the MAPLE reactors be brought back to life? First in a three part series on medical radioisotopes
By Tim Lougheed
February | février 2011 Vol.63, No./no 2
16
Hydrogels: A more human kind of drug delivery By Tyler Irving Pour obtenir la version française de cet article, écrivez-nous à magazine@accn.ca
Departments 4
From the Editor
7
Guest Column By Bernard West
8
Chemical News
Canada's top headlines in the chemical sciences and engineering
Reported and written by Tyler Irving
20
Perfecting the periodic table An excerpt from The Disappearing Spoon
By Sam Kean
29
Society News
30
Chemfusion By Joe Schwarcz
FRom the editor
Executive Director
Roland Andersson, MCIC
Editor
Jodi Di Menna
WriteR
Tyler Irving, MCIC
Graphic Designers
Krista Leroux Kelly Turner
Society NEws
Bobbijo Sawchyn, MCIC Gale Thirlwall
I
Proofreader
n this issue we see how the periodic table of the elements — often regarded as an unchanging bulwark of accumulated knowledge — is, in fact, an animate document, capable of reflecting our ever expanding understanding of the nature of matter. We lead off our news section with a report on how the International Union of Pure and Applied Chemistry is incorporating into the table new information about the molecular weights of isotopes of some elements. To put it all in context, we have excerpted the chapter of Sam Kean’s recent book The Disappearing Spoon in which he explores the current shape of the periodic table and presents alternative ways to graphically express how the elements relate to each other. In our Q and A, we talk to Todd Hoare from McMaster University about his work using hydrogels for targeted drug delivery. Also in this issue, we launch a three part series on medical radioisotopes with a story by Tim Lougheed about the dashed hopes for the MAPLE nuclear reactors and the efforts of those who are trying to rekindle them.
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FEBRUARY 2011 CAnadian Chemical News 5
An Invitation to:
Green Chemistry and Chemical Engineering Delegation to Brazil May 14 – 22, 2011 Sao Paulo and Rio de Janeiro, Brazil Travel to South America with Russell J. Boyd, 2011-2012 candidate for Vice-Chair of the Chemical Instituteof Canada, and Nancy B. Jackson, 2011 president of the American Chemical Society (ACS), as part of the People to People Green Chemistry and Chemical Engineering Delegation. Build lasting partnerships with your peers overseas through formal meetings, discussion sessions, and site visits. Enjoy immersive cultural experiences and take in iconic sights. Make a global impact—not only advancing your field, but also gaining international perspectives.
RSVP by February 15, 2011. For more details, please visit: http://www.peopletopeople.com/OurPrograms/CAP/Pages/jacksonboyd.aspx
Student Chapter Merit Awards Terms of Reference The Student Chapter Merit Awards are offered as a means of recognizing and encouraginginitiative and originality in Student Chapter programming in the areas of chemistry, chemical technology and chemical engineering.
Deadlines • April 1 for Canadian Society for Chemistry • April 1 for Canadian Society for Chemical Technology • June 1 for Canadian Society for Chemical Engineering
Awards The awards consist of an engraved plaque for the winning Chapter and lapel pins for executive members of the Chapter. Also, where appropriate, Honourable Mentions may be given to other Student Chapters by the SelectionCommittees.
Nomination The Chapter should prepare its own nominationand provide an electronic report that includes: • indication of both scientific and social events over the entire 12-month period; • elaboration on what are considered the most important activities; • chapter statistics, including the total numberof active members; • level of participation and interest in each activity; and • photos or other material may be included Submit nominations
electronically:
To Gale Thirlwall at gthirlwall@cheminst.ca
guest column
China: Chemistry Rising
C
hemistry is one of the basic sciences that underpin our way of life. As with everything there is the yin and yang of chemistry. Because of the development of chemical products over the last 200 years our life span has increased very significantly and our quality of life has improved. At the same time the industry has had significant problems with products and by-products that have harmed people and the environment. On balance, I believe the good has outweighed the bad. The chemistry-based industry has reacted with the development of Responsible Care and, more recently, with green chemistry and engineering initiatives, which some prefer to call sustainable chemistry. In the developed countries, chemistry as a career choice has been on the decline. In some nations, university chemical departments have been closed. This is going to lead to a considerable human resource and skill deficit for the existing, and especially for new, commercial initiatives. This dynamic is not the case in the developing economies of China and India and fast growing areas of the world. Chemistry is a subject that attracts the best minds in China. Also, Chinese organisations are prepared to support new developments with resources and quick decisions.
By Bernard West
I will use an example of an initiative in China — and a contrasting lack of initiative in Ontario — to illustrate my point. I recently had a discussion with an award winning entrepreneurial academic. He was frustrated with the lack of speed of commercialisation of new ideas and products coming from his research work. So he went to China to discuss setting up a commercialisation centre at one of the universities. He went on the visit late last year and outlined his plan and his need for money to set up the centre. The university approved his proposal in two weeks and his centre is now about to become operational. Contrast this with the situation concerning the Ontario BioAuto Council (OBAC). The Council focuses on facilitating the rapid commercialisation of new bio-based products for the automotive industry, among others. The Ontario Government took a risk and funded this “skunk works,” almost like an experiment. This was a really great step as the government supplied about $6 million dollars to an industry group to put towards achieving its goals. This type of initiative is used in Israel, one of the most successful commercialisation countries. OBAC has been very successful in that it is now an internationally recognised node of alliances with European, Japanese, South American and U.S. companies and organisations. It has also facilitated the development of 50 new bio-based and bio/petro hybrid-based products. However, the Ontario government has been considering refunding this highly successful initiative for over two years and still has not decided. We will have to begin closing down the initiative soon. There are tremendous technological resources and ideas that have been developed in Canada, but they are being commercialised and their value is being gained in other jurisdictions because we have a risk averseness and lack of leadership in our institutions. Contrast that to the entrepreneurial spirit in China and other places and you can see that we have to change or be left way behind.
Bernard West is the chair of the board of the Ontario BioAuto Council. He also co-chairs the Sustainable Chemistry Alliance and the Canadian Green Chemistry and Engineering Network. Want to share your thoughts on this article? Write to us at magazine@accn.ca
FEBRUARY 2011 CAnadian Chemical News 7
Fundamentals
BIOchemistry
Tweaking the Periodic Table: A Weighty Issue
It may look like a brick wall, but the periodic table of the elements has always been a fluid document, constantly evolving to reflect the latest science. Now, it’s undergoing one of its most substantial changes in a decade with changes to the atomic weights of no fewer than 10 elements. Every two years, the International Union of Pure and Applied Chemistry ( I U PA C ) C o m m i s s i o n o n I s o t o p i c Abundances and Atomic Weights meets to discuss how best to communicate the latest data on various elements. For example, hydrogen in nature is a mixture of two stable isotopes: primarily 1H with a tiny amount of 2H (deuterium). Up to now, the atomic mass was listed as an average value (1.01 atomic units) with an associated range of uncertainty. But this year, the commission decided that uncertainties don’t tell the whole story. Because isotopes of hydrogen are unevenly distributed in nature, “the standard atomic weight that used to be in the table wasn’t actually the atomic weight of any occurrence of hydrogen,” says Michael Wieser, an associate professor at the University of Calgary and secretary of the commission. Atomic weights for hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium will now be stated as intervals, with an upper and lower bound (see t hallium ABOVE). The refinement will be useful to researchers requiring high precision data, but Wieser wants students of chemistry to take note as well. “We’re sort of hoping that this might pique people’s curiosity to explore what’s driving this variability. It actually represents an incredible advance in our knowledge.”
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When you break a bone or tear a ligament, you may pop a painkiller or two. But for people who suffer from chronic pain, those treatments stop working after awhile, leading to a seemingly endless search for relief. Now, for the first time, Canadian and Korean scientists have isolated a protein that they believe is responsible for the maintenance of long-term pain. The work is based on the theory that changes in the brain’s synaptic structure encode pain-related information, in much the same way that memories are stored. One enzyme involved in synaptic changes is called protein kinase M zeta (PKMζ). Experiments on mice showed that levels of this enzyme in the brain were increased immediately following injury. Levels of the phosphorylated form of this enzyme remained high for two weeks afterward, while those for other pain-associated proteins dropped. When PKMζ was inhibited by ζ-pseudosubstrate inhibitory peptide (ZIP), the mice showed decreased long-term sensitization to pain. University of Toronto researcher Min Zhuo, who was part of the team, believes the findings could offer new therapeutic targets for long-term pain. “This is a happy moment for me,” says Zhuo. “We have worked for 10 years to show that chronic pain has an associated mechanism in the brain. But my own feeling is that it’s unlikely that only one protein is involved in maintenance. That’s the next step; we will want to know if there are more proteins like it.”
Pharmaceuticals
Potential New Breed of Antidepressants Found Finding an alternative for the approximately 30 per cent of patients with depression who don’t respond to current medications has long been a goal of mental health researchers. Now, a team at the Centre for Addiction and Mental Health in Toronto has identified a pathway in the brain that could be used as a target for a whole new kind of antidepressant. Fang Liu and her colleagues studied two dopamine receptors in the brain, D1 and D2. It’s known that these receptors occasionally bond to each other, forming a protein complex. While it’s not clear what effect this has on the brain, the researchers discovered that the bonding was more common in the brain tissues of deceased patients who had been diagnosed with depression. They wondered if preventing the bonding would have an antidepressant effect for patients. The team then designed a peptide that would attach to the part of the D1 and D2 receptors that was involved in the bonding. When this peptide was injected into the brains of mice, it performed comparably to conventional antidepressants. “I got very excited, and the drug companies are excited too,” says Liu. “It’s a totally novel target, and a new way to develop an antidepressant.” The team is currently working on a more effective method of delivery, and hopes to begin trials soon.
IUPAC
The atomic weight of 10 elements will now be listed on the periodic table as a range, as in the example of thallium, rather than as a single value, as in the example of iridium. The pie charts show the distribution of the stable isotopes of each element.
Brain Enzyme “Remembers” Past Injury
Chemical News
Canada's top headlines in the chemical sciences and engineering
Law and Policy
BPA Experts Meet, but Don’t Agree The effect of bisphenol A (BPA) on human health continues to be a subject of debate, even among the experts. In early November, Ottawa played host to an international scientific panel convened by the World Health Organization (WHO) with the goal of coming to some kind of consensus. According to the final report, issued in December, that goal is still distant. The report states that most regulatory bodies have converged on “no observable adverse effects limit” (NOAEL) for BPA of 50 mg/kg of body weight per day. This level is thousands of times higher than typical exposure, which is measured in micrograms. Nevertheless, some recent studies suggest certain specific health impacts (impaired sperm parameters and sex-specific neurodevelopment) can be observed even at low exposures. The report stresses the limitations and inconsistencies in many BPA
studies, as well as the difficulties in extrapolating human health risks from animal models. “It is true that science is not foolproof and every study has its flaws,” says Larissa Tasker, a physician in Obstetrics and Gynecology at the Université de Sherbrooke. “But if many studies come to the same conclusion with different methodologies, we should apply the principles of plausibility and consistency.” Warren Foster, a professor in the Department of Obstetrics and Gynecology at McMaster University takes a different view. “I agree with the statements in the report that further research studies are needed,” he says. “But there are other things that people are exposed to at much higher levels that have equivalent or greater bioactivity, and are of greater health concern to me. Nothing new has come out of this report which warrants any action whatsoever.”
Materials Science
New Additive Creates Leaner, Greener Concrete
Stephen Kinrade
The strength of concrete comes from cement, but each tonne of cement produced creates a roughly equal amount of CO2. It’s estimated that global cement production will give off 40 billion tonnes of CO2 per year by 2015. So when Stephen Kinrade and Lionel Catalan of Lakehead University came up with an additive that can reduce the amount of cement in a given volume of concrete, they knew they were onto something big. The admixture - the technical term for a concrete additive - is saccharide-based, although its exact nature can’t be revealed due to pending patents. It is cheap and easy to produce, and can increase the strength of concrete without affecting its other properties, such as workability. “There are additives on the market called super-plasticizers. They Concrete is typically a mixture of cement, fine aggregate (sand), coarse aggregate (gravel) and water. A new additive developed by researchers at Lakehead University increases the strength of the concrete without changing its other properties, such as workability.
improve the workability, but their effect on increasing the strength of concrete depends on adding more cement,” says Catalan. “Ours is completely different; you increase the strength for a given quantity of cement, or you can decrease the quantity of cement and obtain the same strength.” According to calculations, a small quantity of the new additive (one to two kilograms per tonne of concrete) can cut the amount of cement required in half. Kinrade and his team are still working to understand the chemistry of the new additive. In the meantime, the techno logy has been licensed to GreenCentre Canada, which is shopping around for producers. “It will take a chemical company or a cement company that’s interested to market this,” says Catalan, ”but from a technical standpoint, it’s something that already works.”
FEBRUARY 2011 CAnadian Chemical News 9
Nanotechnology
Researchers Grow Nano-scale Patterns on Silicon in 1986. “You just dump your daisies on the surface, and they arrange themselves.” While there are other ways to form similar patterns on silicon, this “molecular hopscotch” method is the first to rely on transferring charge through the underlying layer. The lines could act as guides for nano-scale electrical circuitry.
1
2
3
Atoms of methyl chloride form “daisy chains” on a silicon surface, which could act as guides for wires just one atom in width. Silicon atoms on the surface are represented in blue, chlorine in green, and methyl groups in red. The yellow bubble represents the dangling bond created by charge transfer through the silicon dimer pairs.
John Polanyi
Hopscotch and daisy chains sound like children’s pursuits, but at the molecular level they constitute a whole new way of producing ultrafine patterns on silicon. University of Toronto professor John Polanyi and his graduate student Tingbin Lim worked with a commonly used silicon surface, called Si(100). In this surface, the uppermost layer of atoms is arranged in paired rows. Methyl chloride, a small gaseous molecule, is able to bridge the gap between two of these rows by dissociative attachment. In so doing, it causes electron density to “hop” to the outside silicon atom, creating a high-energy dangling bond. This bond attracts a second methyl chloride molecule, which in turn attracts a third. “If you can do that over and over again, you will have made a chain, just like a daisy chain, right the length of your silicon,” says Polanyi, who won the Nobel Prize for Chemistry
Environment
Water Could Replace Mercury in Fluorescent Bulbs
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electrodesand water vapour. Because his team can grow the nanotubes on almost any shape of substrate, Coulombe believes they could open the door to new geometries for fluorescent bulbs. “Instead of linear tubes, we could build panels, a wall, a ceiling,” he says. And how long before carbon nanotube-water bulbs are on the market? “I would hope within five years, but it all depends on the support that we receive from the big players.”
A plasma discharge from an electrode made of aluminum covered with carbon nanotubes. The gas is mostly argon, but the reddish hue indicates the presence of water vapour. New fluorescent bulbs based on this technology could eliminate the presence of toxic mercury vapour.
Sylvain Coulombe
Environmentalists have good reason to be conflicted about fluorescent light bulbs. True, they are more efficient and longer-lasting than the incandescent variety, but they also contain mercury, a well-known neurotoxin. Now, an accidental discovery at McGill University has led to a new breed of bulb that replaces the mercury with plain old water. Fluorescent bulbs use electrodes to excite plasmas (vapours made of charged particles)
producing light. Many substances can form plasmas, including water. However, water interacts with the complex mix of metals that make up the electrodes, causing them to become brittle and break. Mercury, by contrast, is inert toward most electrodes. Another problem with current electrodes is that they can’t be made very big, due to their need to operate at high temperature. This, in turn, constrains the bulb geometry. Sylvain Coulombe and his team were working on new electrodes, made of carbon nanotubes grown on various metal surfaces, for an unrelated application. In one experiment, the nanotubes became contaminated with water. To their surprise, the water didn’t degrade the electrodes, and actually improved their ability to emit electrons. “That was a total surprise to us,” says Coulombe. “There’s some very complex physics behind this thing, but we know that it works now.” Coulombe and his team have already constructed a new bulb using the carbon
Chemical News
Canada's top headlines in the chemical sciences and engineering water
Oil Sands Water Monitoring Gives Murky Results Canada’s system for monitoring the impact of oil sands extraction on nearby fresh water sources is broken. That’s the conclusion of a flurry of recent reports by scientific panels examining the issue. Toward the end of last summer, a study led by David Schindler at the University of Alberta found that levels of 7 toxic elements (including mercury, lead, and cadmium) in the Athabasca River exceeded Canada’s and Alberta’s guidelines for the protection of aquatic life. This led to the appointment of two scientific review panels: one by Environment Canada, the other by Alberta’s environment ministry. The federal panel delivered its report to thenMinister of the Environment, John Baird, in late December. “Do we have a worldclass monitoring system in place?” asked the panel’s chair Elizabeth Dowdeswell, a former Executive Director of the United Nations Environment Program, at a news conference. “In short, no.” The report listed such shortcomings as a lack of leadership, poor sampling program design, and a failure to communicate results. As of press time, the provincial panel had yet to deliver its report. Meanwhile, a separate report on the oil sands by the Royal Society of Canada, issued in early December, came to similar conclusions. In the area of water quality, it listed such concerns as “appropriateness of data collected, public access to data, independent
scientific oversight, and verification of results.” The federal environment commissioner, Scott Vaughn, also addressed water quality monitoring on the Athabasca in his annual fall report. He pointed out that Environment Canada is not making use of data from the various industry and provincial monitoring programs in the area, and that its own monitoring is woefully inadequate. Environment Canada operates only one water quality monitoring station in the area of the oil sands. What will happen next is unclear. Baird acknowledged his government’s responsibility, saying “we heard the panel’s message loud and clear, and we are ready to act.” He vowed to make progress toward a new monitoring system within 90 days. A day earlier, Alberta’s Environment Minister, Rob Renner, announced his own plan to revamp the monitoring system. However, he estimated it would take until June to be ready. In the meantime, the industry-funded Regional Aquatic Monitoring Program (RAMP) has defended its record. “Contrary to the federal panel’s Report, RAMP incorporates both effects-based and stressor-based monitoring approaches in an effort to establish a more holistic perspective,” said a RAMP spokesperson in an e-mail. RAMP has also made its database publicly available through its website, and plans to supplement the data with summary reports, although as of press time, no timetable for this had been established. The Athabasca River just outside Jasper in Alberta, a few hundred kilometres upstream from the oil sands.
health
Possible Biomarkers of Cancer Aggression Identified Cancer survivors are becoming more common, thanks to early detection and an everexpanding arsenal of treatment options. But knowing when aggressive treatment is necessary and when it isn’t remains a challenge. Researchers at the University of Toronto and Mount Sinai Hospital have recently identified a protein that may provide a measure of cancer’s aggressiveness. The protein is called epithelial adhesion molecule (Ep-CAM). It is a trans-membrane protein: part of it (the extracellular domain, EpEx) protrudes outside the cell, while the rest (the intracellular domain, Ep-ICD) stays in the cytoplasm. Researchers used antibodies to track these two domains in tumours isolated from patients with one of ten cancer types. They found that in the most aggressive cancers, the protein was split apart, with levels of the extracellular domain decreasing, and those of Ep-ICD increasing in the cytoplasm and nucleus. “This is a novel approach, using immunohistochemistry to see how a factor is localized in the cell,“ says Paul Walfish, who led the research. “Right now, all we can say is that it correlates with cancer aggressiveness. It’s a potential breakthrough, but it isn’t necessarily completely validated to everyone’s scien tific satisfaction yet. We need to do more work and to see if we can use it to detect aggressiveness and a potential target.”
The Chemical News is reported and written by Tyler Irving. Want to share your thoughts on our news stories? Write to us at magazine@accn.ca
FEBRUARY 2011 CAnadian Chemical News 11
The aftertaste of
MAPLE For some, the medical radioisotope shortage is reason to breathe new life into the derelict MAPLE reactors. For others, they represent a blunder best forgotten. First in a three part series in which Tim Lougheed traces the dead ends of the past, the frantic scramble of the present, and the blue skies of the future of Canada’s faltering position in the global supply of medical radioisotopes.
By Tim Lougheed
h
hey are a set of boxy, nondescript buildings tucked away in a corner of the Ottawa River valley that most people pass by on their way to somewhere else. They could be seen as the signposts for a road not taken — a long, expensive, and now abandoned bid to grapple with innovative technology. Yet for some observers, they still represent a viable response to a looming healthcare challenge, a solution that was bought and paid for and all but operational. Out of sight, perhaps, but the contents of these pale concrete structures are not necessarily out of mind. They are a pair of small nuclear reactors that became well known by the cheery acronym MAPLE, which stands for Multipurpose Applied Physics Lattice Experiment. Located at the venerable Chalk River Laboratories, about halfway between Ottawa and North Bay, they grew out of this site’s role as the historic cornerstone of nuclear science in Canada. The MAPLEs were originally conceived in the late 1980s to head off a problem that would not become widely recognized for almost 20 years. That problem was providing the global medical community with radioisotopes that play a central part in imaging techniques used for diagnosis and treatment.
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The MAPLE reactors could be seen as the signposts for a road not taken — a long, expensive, and now abandoned bid to grapple with innovative technology. At the heart of this demand is a shiny gray metal, Technetium (Tc), which only has radioactive isotopes, none of them stable. 99Tc in particular serves as an outstanding emitter of gamma rays that can be readily detected by increasingly sophisticated devices such as Single Photon Emission Computed Tomography cameras. The human body’s various internal organs and vital systems can thus be “lit up” for viewing when these isotopes are inserted, making it possible to identify crucial anomalies like abnormal blood flow, hidden abscesses, or tumours. This safe and accepted procedure is now carried out tens of millions of times every year, meeting an obvious need as well as often providing an essential service. If the clinical application of radioisotopes for imaging is relatively straightforward, however, supplying this exotic commodity is anything but. 99Tc has a half-life of just six
Business | RADIOISOTOPES
hours, which minimizes any danger to a patient but means this material must be produced and delivered with “just in time” logistics. The process begins with highly enriched 235U — the same stuff used in weapons — that is bombarded by neutrons in a nuclear reactor to yield a molybdenum isotope, 99Mo, which will subsequently decay to 99Tc. The half-life of this decay is 66 hours, forcing providers to quickly get the 99Mo from the reactor to end-users around the world. As daunting as that prospect may sound, Ottawabased MDS Nordion has emerged as a world leader in making this happen, overseeing the wholesale distribution of radioisotopes to thousands of medical facilities in more than 60 countries. Until fairly recently the company’s primary source of 99Mo was Chalk River, where the National Research Universal (NRU) reactor had been steadily turning out this material from American 235U since the 1970s. Crown corporation Atomic Energy of Canada Ltd. (AECL), originally created to manage this facility, worked out the intricacies of rapidly transporting decaying isotopes by ground and air. The NRU, which had then been in service for fewer than 20 years, provided a reliable source; the market grew, as 99Tc was well on its way to becoming the preferred isotope for medical imaging systems.
When AECL finally and unceremoniously halted all work on the MAPLEs in 2008, it appeared that any progress had been thwarted by technical and administrative difficulties that defied explanation. Over the next decade, this isotope distribution operation was shed from AECL and turned into an independent company, called Nordion International Inc., which was purchased in 1991 by the Canadian health care services firm MDS to create MDS Nordion. Meanwhile, AECL was considering the necessity of a dedicated isotope-manufacturing reactor, a project known as MAPLE X that began in 1988. When AECL subsequently cancelled that undertaking in 1993, the newly formed MDS Nordion launched a protest in the form of a lawsuit. By 1996, the
two enterprises had settled the matter, agreeing to work on a pair of reactors that would ensure continuous isotope output even as each one was taken off-line temporarily for routine maintenance. In the wake of their legal friction, it is possible that AECL and MDS Nordion never managed to set aside their differences. When AECL finally and unceremoniously halted all work on the MAPLEs in 2008, it appeared that any progress had been thwarted by technical and administrative difficulties that defied explanation. In other circumstances, discussion of those difficulties would have remained behind closed office doors or within the pages of technical journals. Instead, they became the focus of extraordinary public scrutiny, since the NRU had just marked its 50th anniversary of operation with an extended shutdown that caused a sudden shortage of radioisotopes. In the aftermath of what was cast as a health care service crisis, the question of what had happened to the MAPLEs eventually surfaced at a House of Commons Standing Committee on Natural Resources. That committee’s official report on the matter did not appear until the end of 2010, even though witnesses testified on these events from mid-2008 to late-2009. They gave widely varying accounts of how the work on the MAPLEs had proceeded, and why nothing had come of it. Politicians cited rising costs and wasted effort; administrators voiced their frustration with delays and a lack of internal communication; regulators underscored the reactors’ inability to meet safety requirements; engineers complained about being prevented from answering key questions surrounding that inability; medical officials reiterated the fundamental importance of finding some assured supply of isotopes for imaging. Much of this commentary revolved around an exceptionally subtle technical point, the MAPLEs’ positive power coefficient of reactivity (PCR). This term refers to the relationship between a reactor’s power level and the reaction taking place inside the reactor vessel. It can be strictly defined as the sum of three measurable factors, linked to the temperature of the surrounding material used to control the reaction, the temperature of the fuel, and the emergence of voids or bubbles within the reactor chamber. Put more simply, when PCR is negative, reactivity inside the reactor decreases as power increases; when PCR is positive, reactivity increases as power increases. The latter situation could be regarded as less safe, since winding down
FEBRUARY 2011 CAnadian Chemical News 13
the power produced by the reactor would apparently increase the intensity of the reaction, perhaps making it difficult to control. Yet a positive PCR can be handled, and need not prevent a reactor from obtaining government certification, says David Mosey, a safety analyst and author of Reactor Accidents, a detailed examination of how this technology can fail. Unfortunately, the MAPLEs were not supposed to have a positive PCR. In fact, there was little that was truly unusual about their design, which was typical of nuclear reactors operating at low pressure, low temperature, with an open tank in a pool of heavy water to regulate neutron fluxes. Even by the standards of research reactors, the whole package was compact and simple, since its exclusive purpose was creating isotopes. Theoretical models of performance indicated that PCR would be negative, so when the first MAPLE was started in 2000 and demonstrated just the opposite, the discovery came as an unwelcome surprise. The Canadian Nuclear Safety Commission, the regulatory authority for this equipment, insisted that the discrepancy had to be explained before any legal sanction could be granted. Years of analysis followed, as AECL sought help from the world’s leading experts in this field. They assembled their own mind-bogglingly complicated models to try and account for the reactor’s behaviour. In the end, everything agreed with the original design calculations that pointed to a negative PCR. No one could explain why it was positive. Harold Smith, who had been responsible for efforts to commission the reactors, told the Standing Committee that he came tantalizingly close to understanding what was happening. “The positive power coefficient of reactivity is not a mystery,” he insisted. “It is not an unsolvable engineering problem. It is a small thermal mechanical effect in a prototype design that requires a simple engineering fix. The power coefficient can be restored to a value of close to zero, and a safety case can be made for these conditions.” Smith noted that the mysterious behaviour of MAPLE was compounded by the fact that an almost identical version of the reactor — built largely with AECL components — had been running for years in Korea. A significant distinction between the two was the latter’s stiffer fuel bundles, leading him to suspect that a slight bowing of those bundles in the MAPLE could have altered its predicted PCR. Along with addressing the impaired flow of water in the surrounding tank as another contributing
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factor, he had been on the verge of testing a method for reducing the PCR to zero. “It is at this point that the project was terminated,” he recalled in a 2008 article for Nuclear Engineering International. “The preparations for the modified fuel bundles were well advanced, having been carried out in parallel with the modifications to remediate the gap water flow.” Hugh MacDiarmid, who had been President and CEO of AECL for just six months when that hard decision was taken, was unapologetic in offering a rationale to the Standing Committee. “We made every effort to solve these mysteries, but the answers were eluding the best minds in nuclear science,” he said. “Furthermore, the costs and timeframes for commissioning and licensing the MAPLEs were increasing in the absence of a technical solution. A second issue related to the uncertainty of the marketplace. The market for isotopes produced by AECL was changing, and it was clear that new sources of supply were coming onstream around the world.”
Others insisted that Canada should not necessarily be investing substantial public resources to become the world’s primary supplier of medical radioisotopes. MacDiarmid’s second point was echoed by others who insisted that Canada should not necessarily be investing substantial public resources to become the world’s primary supplier of medical radioisotopes. By the time the Standing Committee’s report was finally released in 2010, the MAPLEs had sat idle for another year, and an addendum from Conservative members was unequivocal: “The government favours a new paradigm in which Canadians benefit from Canadian-based isotope production, supplemented if necessary from the world market.” MDS Nordion, for its part, has already been moving in this direction. In 2006 the company struck an agreement that assigned AECL all of the financial responsibility for the
MAPLE project, which by then had cost $600 million. The deal also committed AECL to provide MDS Nordion with isotopes for 40 years, and the two firms are once again back in court thrashing out the viability of that prospect. In the meantime, just two days before Christmas MDS Nordion received its first 99Mo shipment from a new supplier in Russia, setting the stage for a vigorous international trade that would compensate for any shortfalls in Canadian production. The agreement is one of several that the company has struck to shore up its supply lines regardless of what might happen in Chalk River or elsewhere. And much could happen. The NRU is expected to keep running until 2016, even as the 2010 federal budget devoted $48 million to study alternative approaches for medical isotope production, such as using cyclotrons. A whole new set of questions surround just how and where Canada will make 99Mo, but it is increasingly unlikely to come from the MAPLE reactors. These facilities are in what AECL describes as an “extended shutdown state,” although some optimistic observers wondered before the Standing Committee about what their status might be.
“The MAPLE reactor project should be reinstated and that sole technical difficulty tackled … we have, over the last few years, made very powerful modifications to transport theory, nuclear reactor calculations, fluid flow, and heat transfer.” “We hope that the MAPLE reactors were simply put in a mothballed state rather than truly dismantled,” said Jean Koclas, a professor with the Nuclear Engineering Institute at Montréal’s École Polytechnique. “It is our opinion, however, that the MAPLE reactor project should be reinstated and that sole technical difficulty be tackled by a group of people involving not only AECL but also those from outside this company, maybe some other organizations, including universities, where we have, over the last
few years, made very powerful modifications to transport theory, nuclear reactor calculations, fluid flow, and heat transfer. I think we should put together the resources to analyze the situation and predict correctly the positive power coefficient so that this technical issue can be solved and the 99Mo and 99mTc problem can be solved once and for all. It is my opinion that this country should put some of its resources into solving this problem.” In its 2010 report, the Standing Committee endorsed this recommendation, but with a specific proviso: “If a private sector proposal is made for the MAPLE reactors that accepts fully the commercial risk associated with the reactors and requires no additional costs on the part of the government, the Committee recommends that the Government of Canada remain open to considering the proposal.” For Jatin Nathwani, Executive Director of the University of Waterloo Institute for Sustainable Energy, that recommendation leaves the door open for the possibility of bringing the MAPLE reactors on line over the next few years in order to forestall problems that will likely crop up with the NRU as that reactor continues to age. In a 2010 book, Canada’s Isotope Crisis, What Next?, which he co-authored with Toronto-based consultant Donald Wallace, they concluded that Canada simply has too much to lose by ignoring what could serve as a major asset and proof of the nation’s competence with nuclear technology. “Having the MAPLEs brought into service within two to three years would synchronize well with having the NRU reactor out of service by 2016,” they wrote. “Significant public funds have been invested in the MAPLE project, and simply to write it off does not seem appropriate, particularly since it came so close to being commissioned and licensed.” They add that such a goal could readily be achieved with an appropriate change in attitude from the regulatory agency and the support of a private sector-led initiative. “This is one way to make good on previous investments and retrieve something of value.” Watch for the next installment in our series on medical radioisotopes in the April issue. Want to share your thoughts on this article? Write to us at magazine@accn.ca
FEBRUARY 2011 CAnadian Chemical News 15
Q Making it All Gel A &
According to one of Canada’s emerging leaders in bioengineering, the key to targeting drug delivery through nanotechnology — for everything from joint pain to cancer treatment — will be found in hydrogels. By Tyler Irving
M
cMaster University’s Todd Hoare creates polymer-based hydrogels that, unlike previous generations of biomaterials, are designed to change their properties in response to the dynamic environment inside the human body. The work encompasses aspects of nanotechnology, polymer science and pharmaceuticals. Last fall, Hoare was recognized with a Polanyi Prize, an award given by the Ontario government to outstanding young researchers in the early stages of their careers. ACCN spoke with Todd Hoare to find out more about the ground he’s breaking.
ACCN: With your recent prize, your research is getting
some attention, including your work on gel-based particles. What is your definition of a gel?
are not particularly safe themselves even though the polymers have excellent biological safety. So there has been a lot of concerns about using some of these materials biologically on that basis, because we don’t really know what happens to them long term. So what we’re doing in my lab is we’re making very short chains of these synthetic polymers; things that are less than the molecular weight that your kidneys can clear, so your body can filter them out, and we’re connecting those short chains with biodegradable linkages. We’re trying to capture all the properties and behaviours of synthetic polymers that are favourable — that we can tune them however we want, we can put in different functional groups very easily — we want to capture all that richness of chemistry, but also to do that in a form that can degrade and be cleared, that is not going to accumulate in your body.
T.H.: We work on hydrogels and particle-based gels called
microgels. They’re basically hydrogels on a micron or nanotype scale. We view a gel as a material that is composed of polymers that are themselves water soluble, but are crosslinked together in some way so they can’t dissolve. We create the hydrogel, swell it with water and then change the conditions of that water; we heat it up, we change the pH, change the solvent conditions, and that way we can contain more or less of the water inside. So we get some dynamics in terms of swelling, de-swelling, average pore sizes, and so on. ACCN: And some of these gels can biodegrade? T.H.: That’s true. And that’s what we’re working on now.
One of the traditional problems with most conventional hydrogels is that they’re based on carbon-carbon bond backbones. They’re synthetic polymers so once you put them in the body, essentially, they’re there until you die. There’s no obvious mechanism [by which they degrade], or if there is a way in which they degrade, you could actually create unsafe products with depolymerization since some of the monomers
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Todd Hoare in his lab at McMaster University, next to a high performance liquid chromatograph which his team uses to accurately measure low concentrations of drugs in order to study how hydrogels release medicine.
Chemical Engineering | HYDROGELS
ACCN: What are the potential applications for
ACCN: Are there any technologies that release drugs
these hydrogels?
slowly right now?
T.H.: There’s a few applications. The one we’re most
T.H.: There are, yes, but most of them are hard, insoluble
i nterested in by far is drug delivery. The hydrogels have a very high free volume inside of them because there’s a lot of solvent in them, so we can load a lot of drugs inside. And by changing how they swell in different environments — so whether we heat them up in a specific environment or whether we go from an area that’s acidic to basic, for example — we can cause these things to swell and deswell and thus change the rate of drug release from the materials. So that’s our main interest, but there’s also a lot of interest for tissue engineering applications. Particularly, the hydrogels we’re making now are injectable. You basically start with liquid-like precursors outside the body and when you inject them into the body, they gel very quickly. So we can entrap cells inside that material at the same time and that should enable us to aid in tissue engineering depending on what the hydrogel is.
type polymers and most of them have degradation products that are fairly acidic. As they break down, you often get acidic products which can cause problems in the body. Also, because they’re very hard, they’re basically insoluble polymer blocks. The body doesn’t respond to them in the same way. Proteins stick to them more, they don’t have the same sort of mechanical and chemical structure that the matrix of cells are used to, which hydrogels do. So typically, you get more severe inflammatory or immune responses from these when placed inside the body than you do with a hydrogel-based system. That’s why we’re trying to engineer these hydrogel systems to achieve these long periods of release, because we have some biological advantages.
ACCN: So the gel acts as a scaffold for
tissue engineering? T.H.: Exactly. And we can change how quickly it degrades
ACCN: So they are closer in their properties to the
cell’s own tissues than the materials that have traditionallybeen used? T.H.: Absolutely. ACCN: And that’s the real advantage of them?
depending how quickly the cells grow and form the tissue.
T.H.: It is. The cells don’t feel the environment is foreign to
ACCN: Let’s go back to drug delivery application for
them; they’re mechanically similar, we can engineer the chemistry to be similar, so that’s certainly a huge advantage for any type of application where the material is inside the body.
a second. You mentioned there’s a lot of space in betweenthe pores of these gels. Why doesn’t the drug wash right out? What holds it in there? T.H.: That’s the advantage of having these synthetic
networks that we can control really tightly. We can put functional groups or chemistries inside those networks that can either actually react with the drug, so we can actually get a degradable bond between the polymer and the drug so it will release slowly, or it can just interact. We’ve seen that if you put even opposite charges — so a positive charge on the drug and a negative charge on the polymer chain — these can interact and significantly slow the release. In some hydrogels that we’ve been working on, we’ve achieved up to almost two months of release of small molecules just by changing the chemistry of the hydrogel and how that hydrogel interacts with the chemistry of the drug we’re trying to deliver.
ACCN: You’re also working on controlling the size
of the nanoparticles. Why is that important? T.H.: What we found is that, depending on how big you make
these particles, the body does very different things with them. So on a micron-type scale, the particles generally stay where you inject them. If you reduce the size to 200 or 100 nanometres, sometimes the cells will take them up into the centre of the cell, so they’re not just outside, they’re actually taken internally into the cell. So we can deliver things like DNA or other genetic materials for gene therapy. We’ve shown that that’s possible. In other cases, depending on the surface chemistry, they don’t get taken into the cells, but they do get moved very quickly. So, even within a day or two, if you inject a lot of these particles at one site, and you look a day or two later, they’re completely gone. They’ve been moved
FEBRUARY 2011 CAnadian Chemical News 17
Celsius with a resolution of one to two degrees Celsius. We’ve made gels that can be swollen at 37 and shrink at 38 or 39 degrees Celsius, which is the typical temperature at an inflammation site, for example, or at a cancerous tumour. We’ve made microgels that over a very narrow range of pH, maybe .1 or .2 pH units, can stick together or not stick together. So again, anything metabolically active will be slightly more acidic, so we can deliver things to that location. That’s of real interest in terms of actually being able to localize drug delivery to a place that’s specific inside the body, using these biomolecular and physical cues. Injectable hydrogels are made by mixing two reactive polymers — one functionalized with aldehyde groups and another functionalized with hydrazide groups — to form a degradable, hydrazone-bonded network. A double-barrelled syringe mixes the polymers by co-extruding them through a mixer at the end of the syringe, converting a low viscosity polymer solution to a hydrogel within seconds.
away by the inflammatory cells. Circulation is the third thing we can look at. The smaller the particle, the longer it tends to circulate. So if we want to target a particular tissue, a cancerous tumour, for example, that’s an advantage. We have a lot of control over where they go, how long they stick around wherever we want them, and also whether they stay outside cells or go inside cells, by changing the particle size.
ACCN: Are these polymers made of particularly exotic
materials or are they just clever engineering of the polymers that we already use all the time? T.H.: The polymer that we use a lot is poly(N-isopropylacryl-
amide. I think 1968 was the first paper on them, so they have been around for awhile. They have been investigated for use in oil recovery, those types of applications, just because they can basically take up water and release water. I wouldn’t call it exotic, but it’s not something you’d go and buy off the shelf at a tonnes scale either. It’s still a specialty material. ACCN: One thing that strikes me about your work is
can you give me some more examples of how that might work?
how interdisciplinary it is. You started off in chemical engineering, but you’re working with oncologists, physicians, all kinds of people in all sorts of medical fields. How does this affect how you do your research?
T.H.: Our main interest is working on microgels that have
T.H.: I think, particularly if you’re in the biomedical space,
temperature sensitive properties. As we heat them up past a particular temperature, they shrink. What we’ve found is that we can use biological triggers — for example, the blood has a different protein concentration than the space around your cells, or a cancerous tumour will have a slightly different temperature and a slightly different pH than the surrounding tissue because they are metabolically active, so they have more acid byproducts, more heat being produced because of metabolism — to cause particles to aggregate together or shrink to release drugs specifically at particular sites that we’re interested in in the body.
or you’re interested in looking at biomedical applications, it’s absolutely impossible to do any impactful research without collaborating. There’s just so much that you need to know in order to design something and see how it works. I know a little bit about biology and medicine, but [as an engineer] half the time you’re not even sure what types of treatments are needed, or what types of physical cues are reflective of those conditions. Just talking with people like doctors, oncologists, they give you ideas in that they’ve identified a problem based on their experience, so they may give you some information on how to design a material to address their need as well. I think people who are in biomedical research have a hard time identifying one thing they’re good at, you have to know a little bit about a lot of things in order to be effective.
ACCN: The interaction of the particles and biomolecules:
ACCN: And they’re sensitive enough to react to that
tiny change in temperature? T.H.: Yes, actually. It’s a very discontinuous response. We can
tune the temperature to anywhere between 20 to 50 degrees
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Want to share your thoughts on this article? Write to us at magazine@accn.ca
Young Investigator Award for Organic Chemistry
Bourse Jeune Chercheur en Chimie Organique
Applications are invited for the Boehringer Ingelheim Young Investigator Award for Organic Chemistry. This award is intended to support research in synthetic organic chemistry by new faculty members at Canadian universities. Faculty members whose research interests lie in related areas (e.g. bio-organic, physical organic, medicinal chemistry or structure-based drug design) but include a significant synthetic organic chemistry component are encouraged to apply. The award consists of an unrestricted research grant of $20,000 per year for three years. Applicants: • Must hold a faculty position at a Canadian university. • Should not have been a faculty member for more than six years as of May 1, 2011. Applications should: • Include the curriculum vitae of the applicant and a description of the research which would be carried out under this award. • Include a research proposal of no more than five pages in length. • Be followed by three letters of support written by scientists familiar with the applicant and his or her research. These supporting letters should not accompany the application but should be sent directly to the address below. Applications will be judged by senior members of the scientific staff of Boehringer Ingelheim (Canada) Ltd./Ltée based on the excellence of the applicant and his or her research proposal. Applications and supporting letters will be accepted until June 1, 2011. The recipient of this award will be informed by June 30, 2011. For confidential consideration, applications should be submitted to the Vice President, Chemistry.
Paul J. Edwards Vice President, Chemistry / Vice-président, Chimie
Nous sollicitons les candidatures pour la Bourse Boehringer Ingelheim, Jeune Chercheur en Chimie Organique. Cette bourse a pour but de soutenir la recherche en chimie organique de synthèse dirigée par de nouveaux professeurs d’universités canadiennes. Ainsi, les professeurs dont les intérêts de recherche résident dans des domaines connexes (par exemple, la chimie bio-organique, physico-organique ou la conception de médicaments assistée par modélisation) comprenant une composante importante de chimie organique de synthèse sont encouragés à poser leur candidature. La bourse consiste en un octroi de recherche sans restriction et s’élève à un montant de 20 000 $ par année pendant trois ans. Les candidats : • Doivent détenir un poste de professeur dans une université canadienne. • Ne doivent pas avoir été membre du corps professoral depuis plus de six ans en date du 1er mai 2011. Les demandes doivent : • Inclure le curriculum vitæ du candidat ainsi qu’une description de la recherche qui serait mise à exécution à l’aide de cette bourse. • Inclure une proposition de recherche ne devant pas excéder cinq pages. • Être suivies par trois lettres de recommandation écrites par des scientifiques familiers avec le candidat et son domaine de recherche. Ces lettres ne doivent pas accompagner les dossiers de candidatures, mais plutôt être envoyées directement à l’adresse indiquée ci-dessous. Les candidatures seront évaluées par le personnel scientifique senior de Boehringer Ingelheim (Canada) Ltd./Ltée en se basant sur l’excellence du candidat et de sa proposition de recherche. Les candidatures et les lettres de recommandation seront acceptées jusqu’au 1er juin 2011 et le récipiendaire de cette bourse sera informé du résultat au plus tard le 30 juin 2011. Les candidatures doivent être soumises, sous pli confidentiel, à l’attention du vice-président, Chimie.
Boehringer Ingelheim (Canada) Ltd./Ltée Recherche et développement
* La forme masculine utilisée désigne autant les femmes que les hommes.
2100, rue Cunard, Laval, QC H7S 2G5 Tel./Tél. : 450-682-4640 Fax/Téléc. : 450-682-4189
Above (and Bey the Periodic Ta In his recent book The Disappearing Spoon, and Other Tales of Madness, Love, and the History of the World From the Periodic Table of the Elements, American writer Sam Kean recounts the stories behind the building of one of humankind’s greatest scientific achievements. Here, we excerpt part of the chapter in which Kean asks how the periodic table, a bulwark of chemistry, might be adapted to reflect what scientists continue to uncover about the nature of the elements. By Sam Kean
I
f aliens ever land and park here, there’s no guarantee we’ll be able to communicate with them, even going beyond the obvious fact they won’t speak “Earth.” They might use pheromones or pulses of light instead of sounds; they might also be, especially on the off off chance they’re not made of carbon, poisonous to be around. Even if we do break into their minds, our primary concerns — love, gods, respect, family, money, peace — may not register with them. About the only things we can drop in front of them and be sure they’ll grasp are numbers like pi and the periodic table. Of course, that should be the properties of the periodic table, since the standard castles-with-turrets look of our table, though chiselled into the back of every extant chemistry book, is just one possible arrangement of elements. Many of our grandfathers grew up with quite a different
table, one just eight columns wide all the way down. It looked more like a calendar, with all the rows of the transition metals triangled off into half boxes, like those unfortunate 30s and 31s in awkwardly arranged months. Even more dubiously, a few people shoved the lanthanides into the main body of the table, creating a crowded mess. No one thought to give the transition metals a little more space until Glenn Seaborg and his colleagues at (wait for it) the University of California at Berkeley made over the entire periodic table between the late 1930s and early 1960s.
The standard castles-withturrets look of our table, though chiselled into the back of every extant chemistry book, is just one possible arrangement of elements. It wasn’t just that they added elements. They also realized that elements like actinium didn’t fit into the scheme they’d grown up with. Again, it sounds odd to say, but chemists before this didn’t take periodicity seriously enough. They thought the lanthanides and their annoying chemistry were exceptions to the normal periodic table rules — that no elements below the lanthanides would ever bury electrons and deviate from transition-metal chemistry in the same way. But the lanthanide From the book The Disappearing Spoon by Sam Kean. © 2010 by Sam Kean. Reprinted by permission of Little, Brown and Company, New York, NY. All rights reserved.
20 L’Actualité chimique canadienne
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Chemistry | PERIODIC TABLE
yond) able chemistry does repeat. It has to: that’s the categorical imperative of chemistry, the property of elements the aliens would recognize. And they’d recognize as surely as Seaborg did that the elements diverge into something new and strange right after actinium, element eighty-nine. Actinium was the key element in giving the modern periodic table its shape, since Seaborg and his colleagues decided to cleave all the heavy elements known at the time — now called the actinides, after their first brother — and cordon them off at the bottom of the table. As long as they were moving those elements, they decided to give the transition metals more elbow room, too, and instead of cramming them into triangles, they added ten columns to the table. This blueprint made so much sense that many people copied Seaborg. It took a while for the hard-liners who preferred the old table to die off, but in the 1970s the periodic calendar finally shifted to become the periodic castle, the bulwark of modern chemistry. But who says that’s the ideal shape? The columnar form has dominated since Mendeleev’s day, but Mendeleev himself designed thirty different periodic tables, and by the 1970s scientists had designed more than seven hundred variations. Some chemists like to snap off the turret on one side and attach it to the other, so the periodic table looks like an awkward staircase. Others fuss with hydrogen and helium, dropping them into different columns to emphasize that those two non-octet elements get themselves into strange situations chemically. Really, though, once you start playing around with the periodic table’s form, there’s no reason to limit yourself to rectilinear shapes. One clever modern periodic table looks
Ti
V
Cr
Mn
Fe
Co
Ni
like a honeycomb, with each hexagonal box spiralling outward in wider and wider arms from the hydrogen core. Astronomers and astrophysicists might like the version where a hydrogen “sun” sits at the centre of the table, and ll the other elements orbit it like planets with moons. Biologists have mapped the periodic table onto helixes, like our DNA, and geeks have sketched out periodic tables where
Some chemists like to snap off the turret on one side and attach it to the other, so the periodic table looks like an awkward staircase. rows and columns double back on themselves and wrap around the paper like the board game Parcheesi. Someone even holds a U.S. patent (#6361324) for a pyramidal Rubik’s Cube toy whose twistable faces contain elements. Musically inclined people have graphed elements onto musical staffs, and our old friend William Crookes, the spiritualist seeker, designed two fittingly fanciful periodic tables, one that looked like a lute and another like a pretzel. My own favourite tables are a pyramid-shaped one — which very sensibly gets wider row by row and demonstrates graphically where new orbitals arise and how many more elements fit themselves into the overall system — and a cutout one with twists in the middle, which I can’t quite figure out but enjoy because it looks like a Möbius strip.
FEBRUARY 2011 CAnadian Chemical News 21
bioindustry
We don’t even have to limit periodic tables to two dimensions anymore. The negatively charged antiprotons that Segrè discovered in 1955 pair very nicely with antielectrons (i.e. positrons) to form anti-hydrogen atoms. In theory, every other anti-element on the anti-periodic table might exist, too. And beyond just that looking-glass version of the regular periodic table, chemists are exploring new forms of matter that could multiply the number of known “elements” into the hundreds if not thousands.
Thirteen aluminum atoms grouped together in the right way do a killer bromine: the two entities are indistinguishable in chemical reactions. First are superatoms. These clusters — between eight and one hundred atoms of one element — have the eerie ability to mimic single atoms of different elements. For instance, thirteen aluminum atoms grouped together in the right way do a killer bromine: the two entities are indistinguishable in chemical reactions. This happens despite the cluster being thirteen times larger than a single bromine atom and despite aluminum being nothing like the lacrimatory poison-gas staple. Other combinations of aluminum can mimic noble gases, semiconductors, bone materials like calcium, or elements from pretty much any other region of the periodic table. The clusters work like this. The atoms arrange themselves into a three-dimensional polyhedron, and each atom in it mimics a proton or neutron in a collective nucleus. The caveat is that electrons can flow around inside this soft nucleic blob, and the atoms share the electrons collectively. Scientists wryly call this state of matter “jellium.” Depending
on the shape of the polyhedron and the number of corners and edges, the jellium will have more or fewer electrons to farm out and react with other atoms. If it has seven, it acts like bromine or a halogen. If four, it acts like silicon or a semiconductor. Sodium atoms can also become jellium and mimic other elements. And there’s no reason to think that still other elements cannot imitate other elements, or even all the elements imitate all the other elements — an utterly Borgesian mess. These discoveries are forcing scientists to construct parallel periodic tables to classify all the new species, tables that, like transparencies in an anatomy textbook, must be layered on top of the periodic skeleton. Weird as jellium is, the clusters at least resemble normal atoms. Not so with the second way of adding depth to the periodic table. A quantum dot is a sort of holographic, virtual atom that nonetheless obeys the rules of quantum mechanics. Different elements can make quantum dots, but one of the best is indium. It’s a silvery metal, a relative of aluminum, and lives just on the borderland between metals and semiconductors. Scientists start construction of a quantum dot by building a tiny Devils Tower, barely visible to the eye. Like geologic strata, this tower consists of layers — from the bottom up, there’s a semiconductor, a thin layer of an insulator (a ceramic), indium, a thicker layer of a ceramic, and a cap of metal on top. A positive charge is applied to the metal cap, which attracts electrons. They race upward until they reach the insulator, which they cannot flow through. However, if the insulator is thin enough, an electron — which at its fundamental level is just a wave — can pull some voodoo quantum mechanical stuff and “tunnel” through to the indium. At this point, scientists snap off the voltage, trapping the orphan electron. Indium happens to be good at letting electrons flow around between atoms, but not so good that an electron disappears inside the layer. The electron sort of hovers instead, mobile but discrete, and if the indium layer is thin enough and narrow enough, the thousand or so indium
FEBRUARY 2011 CAnadian Chemical News 23
Canadian Society for Chemical Engineering
2011 CSChE Chemical Engineering Local Section Scholarships The Canadian Society for Chemical Engineering offers two CSChE Chemical Engineering Local Section Scholarshipsannually to undergraduate students in chemical engineering at a Canadian university. Sponsoredby the Edmonton CSChE, Sarnia CIC, and London CIC Local Sections. Deadline: April 30, 2011 For details visit www.chemeng.ca/ls_scholarships. CSChE
“ Green, Clean and Sustainable”
Canada
Seminar and 2011 SCI/CIC Awards Dinner
Thursday, March 24, 2011 | Hyatt Regency Toronto The Canadian section of the Society of Chemical Industry (SCI) and the Chemical Institute of Canada (CIC) will be hosting an afternoon seminar series followed by the annual awards ceremony and dinner. The seminar will feature leaders from industry who will speak on a range of topics relating to green chemistry and engineering, followed by an awards dinner in recognition of those who have made outstanding achievements in service, industry, and leadership. Featured speakers include Richard Paton and Bob Masterson representing the Chemistry Industry Association of Canada (CIAC); Rui Resendes, GreenCentre Canada; Murray McLaughlin, Sustainable Chemistry Alliance; and Craig Crawford, Ontario BioAuto Council. Join us to participate in the seminar series and to celebrate the success of the 2011 award winners.
To register, please visit www.cheminst.ca/sci_awards. For more information, please contact scidinner@cheminst.ca or call Michelle Moulton at (613)232-6252 ext. 229.
atoms band together and act like one collective atom, all of them sharing the trapped electron. It’s a superorganism. Put two or more electrons in the quantum dot, and they’ll take on opposite spins inside the indium and separate in oversized orbitals and shells. It’s hard to overstate how weird this is, like getting the giant atoms of the Bose-Einstein condensate but without all the fuss of cooling things down to billionths of a degree above absolute zero. And it isn’t an idle exercise: the dots show enormous potential for next-generation “quantum computers,” because scientists can control, and therefore perform calculations with, individual electrons, a much faster and cleaner procedure than channelling billions of electrons through semiconductors in Jack Kilby’s fiftyyear-old integrated circuits. Nor will the periodic table be the same after quantum dots. Because the dots, also called pancake atoms, are so flat, the electron shells are different than usual. In fact, so far the pancake periodic table looks quite different than the periodic table we’re used to. It’s narrower, for one thing, since the octet rule doesn’t hold. Electrons fill up shells more quickly, and nonreactive noble gases are separated by fewer elements. That doesn’t stop other, more reactive quantum dots from sharing electrons and bonding with other nearby quantum dots to
In fact, so far the pancake periodic table looks quite different than the periodic table we’re used to. form . . . well, who knows what the hell they are. Unlike with superatoms, there aren’t any real-world elements that form tidy analogues to quantum-dot “elements.” In the end, though, there’s little doubt that Seaborg’s table of rows and turrets, with the lanthanides and actinides like
moats along the bottom, will dominate chemistry classes for generations to come. It’s a good combination of easy to make and easy to learn. But it’s a shame more textbook publishers don’t balance Seaborg’s table, which appears
The current periodic table has served us well so far, but reenvisioning and recreating it is important for humans. inside the front cover of every chemistry book, with a few of the more suggestive periodic table arrangements inside the back cover: 3D shapes that pop and buckle on the page and that bend far-distant elements near each other, sparking some link in the imagination when you finally see them side by side. I wish very much that I could donate $1,000 to some nonprofit group to support tinkering with wild new periodic tables based on whatever organizing principles people can imagine. The current periodic table has served us well so far, but reenvisioning and recreating it is important for humans (some of us, at least). Moreover, if aliens ever do descend, I want them to be impressed with our ingenuity. And maybe, just maybe, for them to see some shape they recognize among our collection. Then again, maybe our good old boxy array of rows and turrets, and its marvellous, clean simplicity, will grab them. And maybe, despite all their alternative arrangements of elements, and despite all they know about superatoms and quantum dots, they’ll see something new in this table. Maybe as we explain how to read the table on all its different levels, they’ll whistle (or whatever) in real admiration — staggered at all we human beings have managed to pack into our periodic table of the elements. Want to share your thoughts on this article? Write to us at magazine@accn.ca
FEBRUARY 2011 CAnadian Chemical News 25
Manulife
Nominate Your Faculty Advisor Has your faculty advisor taken an active role in working with your Student Chapter throughout the year? Why not recognize him or her with one of the Faculty Advisor Awards? Three awards are given annually, one per Society. Terms of Reference are available at www.cheminst.ca/faculty_advisor.
Nominations due
March 30, 2011.
“It’s Chemistry, Eh!?” Announcing International Year of Chemistry contest. As part of the International Year of Chemistry Middle and high school students are eligible to win $2,500 towards further education just by submitting a three-minute chemistry-themed video.
Contest opens February 1, 2011 – April 22, 2011. Winners will be announced June 3, 2011. For a full list of contest rules and details visit www.iyc2011.ca
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Chemical Institute of Canada
become a Member Network with fellow science and engineering professionals. *** Exchange cutting-edge information. *** Participate in the enhancement of your profession. *** Engage the next generation.
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Society news Chemical Education Fund
An EPIC Start to a New Program for High School Students By Horace Luong
Accreditation
CSC Accreditation Committee Makes its Mark in Qatar by Jan Kwak
Two young women who participated in the Enrichment Program in Chemistry at the University of Manitoba this winterwork to determine the vitamin C content of various food products.
The fall of 2010 marked the start of the Enrichment Program in Chemistry (EPIC) at the University of Manitoba. For five Saturday mornings, from November to February, 22 high school and homeschooled students from across Winnipeg gathered at the University of Manitoba to learn about and experience the multifaceted nature of chemistry. The program was funded by the University of Manitoba and the CIC Chemical Education Fund. EPIC provides opportunities for young students to explore various branches of chemistry by conducting experiments. This year, participants learned about vitamin C and determined its concentration in various food products, extracted caffeine from tea, and looked at the connection between art and chemistry. A short discussion prior to each experiment addressed a particular discipline of chemistry and provided the necessary background knowledge to conduct the experiment. A handful of University of Manitoba undergraduate student volunteers coached participants during the sessions. The volunteers, from various science disciplines, shared their diverse undergraduate experiences with the participants. EPIC participants who are in either their last or next-to-last year in high school, were keen to learn about the paths the undergraduates have pursued. Planning is already underway to build on the EPIC program for next year.
Four students from the BSc chemistry major program at Qatar University in Doha, Qatar convocated last June, making them the first graduates of the program after its accreditation by the Accreditation Committee of the CSC in 2009. Chaired by John McIntosh, FCIC, the CSC’s Accreditation Committee has been active in the assessment of chemistry programs at a number of international universities, most notably in the middleeast where five universities have now received full CSC accreditation. In a new initiative, the CSC now provides graduating students with a certificate, and on October 27, 2010 the Department of Chemistry and Earth Sciences of Qatar University celebrated the award of the CSC certificates to its first group of graduating students — Asia Al-Jabery, Fatma Alemadi, Sara Al-Mari and Thoraya Haydar — who , notably, are all women. In his opening comments, the Head of the Department, Jan Kwak, FCIC noted the importance Qatar University places on the accreditation of its chemistry program by the CSC, and the important role the international accreditation program of the society is playing in setting standards for universities in theory and especially laboratory courses that are fully equivalent to the programs in Canadian universities.
Fatma Alemadi and Thoraya Haydar, two of the women who graduated last summer from the newly-accredited chemistry program at Qatar University, pose with their certificates and other members of the chemistry department last October.
Students
Crystal Champs Crowned The winning crystals in the “best overall” category — judged on size, quality and weight — of The National Crystal Growing Competition are displayed (left) in order of rank, with number 1 taking first place. Laurie Lalancette and Yannick Fleurent of École Secondaire Natagan, Barraute, Que. were the cultivators of the winning Copper II Sulfate dandy. Oliver Sun, Kathleen Nash and Patricia Quek of Fredericton High School in Fredericton, N.B. took second place and Sanjeev Narayanaswamy of George S. Henry Academy in Toronto, Ont. came in third.
Alec Curren and Sam Chilton of A.Y. Jackson Secondary School in Kanata, Ont. placed first in the “best quality” category and Paul St-Louis of Fellowes High School in Pembroke, Ont. walked away with the “best teacher crystal” prize. The annual contest is a fun, hands-on experience for high school students and their teachers, organized by the CIC. In memoriam
The CIC wishes to extend its condolences to the families of John R. B. Boocock, FCIC, John F. Goudey, MCIC and Gerald W. King, FCIC.
FEBRUARY 2011 CAnadian Chemical News 29
Chemfusion
Polyfunctional Polycarbonate By Joe Schwarcz
Y
ou really have to do something major to have a street named after you. You can thrill the world with music, you can make an impact in politics, you can become a star athlete, or like Daniel Fox, you can invent a plastic. Dan Fox Drive in Pittsfield, Mass. is a tribute to the man who gave the world polycarbonate, a plastic that was to profoundly alter our lives. Fox graduated with a PhD from the University of Oklahoma in 1952 and soon found a job as a research chemist with General Electric in Schenectady, N.Y. At the time, G.E. researchers were looking for novel materials to be used as insulation for electric wires but were repeatedly stymied. Every material they tried deteriorated when exposed to water. It was at this point that Fox remembered a curious substance he had encountered in graduate school. He had been working with guiacol, a compound that was found in creosote, the black oily guck that builds up inside chimney flues as a result of incomplete burning of wood or coal. There was interest in guiacol because of its potential to be converted into compounds that had applications in the pharmaceutical and food industries. Guiacol itself had antiseptic properties and also served as a potential raw material for the synthesis of
30 L’Actualité chimique canadienne
vanillin, the major flavour component of the vanilla bean. As part of his research, Fox synthesized a number of guiacol derivatives, one of which was guiacol carbonate. Interestingly, this compound resisted breakdown, even in boiling water. At the time this didn’t seem to have any great importance, but now at G.E., Fox was searching for just such a material. Guiacol carbonate was water resistant all right, but it was a simple molecule that could not be formulated into any sort of a plastic. But Fox understood how carbonates were synthesized and realized that if he started with the right ones he could link them together into long chains, in other words, into “polycarbonates.” There was a good chance that such a polymer would have the properties he desired. Alas, when he mixed his chemicals, all he got was a glob of a material that was so hard he couldn’t even remove his stirring rod. This was certainly not going to be any sort of insulating material. But it was interesting enough to keep around the lab. The glob became a curiosity, sometimes used to drive nails, sometimes thrown down stairs in futile attempts to shatter it. No luck with that. Hmmm, Fox thought, a plastic that doesn’t break ought to be patented! And in 1955, just two years after he had come across the novel material, Fox applied for a patent. As is routine with any new patent application, he carried out a patent search and discovered much to his amazement that the German chemical company Bayer had applied for a polycarbonate patent the same year! Apparently, Hermann Schnell at Bayer had independently come up with a plastic almost identical to Fox’s. Since neither patent had yet been granted, the two companies held discussions and forged a working agreement.
février 2011
Whichever company was granted legal priority, it would allow the other one to manufacture polycarbonate as long as appropriate royalties were paid. The patent was awarded to Bayer since the company was able to document that Schnell had invented polycarbonate a week before Fox gave birth to his discovery. Polycarbonate, it seems, had two legitimate fathers! As it turned out, the agreement worked in G.E’s favour. Before long, they found uses for the new plastic, and the product was off and flying. In fact, it was flying into outer space! Astronauts’ helmets had to be able to withstand impact at both high and low temperatures, and the visors had to have exceptional clarity. Polycarbonate fit the bill. That “one small step for man, one giant leap for mankind” could not have been taken without polycarbonate. The plastic also leaped into car headlight assemblies, safety glasses, bullet resistant shields, fighter plane canopies, skylights, and “unbreakable” bottles. A polycarbonate tunnel allowed visitors at SeaWorld to walk through a shark tank. Many viewed the predators through lightweight, shatterproof plastic eyeglasses made of polycarbonate. Then along came the electronic age, essentially made possible by poly carbonate. Computer casings, cell phones, and perhaps most importantly, compact discs and DVDs are all made of this remarkable plastic. It’s the only one that meets the strength, weight and optical purity characteristics needed for compact audio and video discs. Our life would truly be different without this plastic. Joe Schwarcz is the director of McGill University’s Office for Science and Society. Read his blog at chemicallyspeaking.com. Want to share your thoughts on this article? Write to us at magazine@accn.ca