NEWS OF THE WEEK
COU RT ESY O F GEO RGE WHIT ESIDES
‘INFOFUSE’ GETS MESSAGE ACROSS COMMUNICATIONS: New technology transmits chemically encoded messages
C When an infofuse is lit, a succession of metallic dots burn (from top to bottom), producing a series of spectral signatures that can convey an encoded message.
HEMICALLY CODED FLARES may one day join
the ranks of telecommunication methods. In a chemical analog of Morse code transmission, burning a metal-treated material reveals a message to a remote viewer. Harvard University chemistry professor George M. Whitesides, postdoc Samuel W. Thomas III, and their colleagues devised the chemical communication technique, which they call an “infofuse” (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0902476106). With further development, this proof-of-concept technology could be used in applications such as a device to transmit information during a rescue operation, Thomas says. Or it could be combined with a sensor in a device that would transmit a warning signal when, say, a pollutant was detected in the environment, he adds. The researchers encode a message by applying a suc-
ISOTOPE SHORTAGE RETURNS PHARMACEUTICALS: Shutdown of Canadian nuclear reactor threatens medical diagnostics
PLOS M EDICINE
Technetium-99m is used in medical diagnostic imaging procedures such as the heart stress test.
T
HE GLOBAL SUPPLY of medical isotopes has
been disrupted for the second time in less than a year—this time by the temporary shutdown of a nuclear reactor in Canada. The reactor, in Chalk River, Ontario, will be out of service for more than three months while its operator, Atomic Energy of Canada, investigates a heavy-water leak. The facility is a major source of molybdenum-99, which is used to generate technetium-99m for diagnostic nuclear medical procedures such as cardiac blood-flow imaging, bone scanning for secondary tumors, and renal function monitoring. The reactor produces 30 to 40% of the world’s medical isotopes and approximately 50% of those used in North America, esWWW.CEN-ONLINE.ORG
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cession of dots of various alkali metals on a fuse made of a nitrocellulose strip. To demonstrate the concept, they created a code in which a particular combination of metal dots corresponds to a particular alphanumeric character. The letter c, for example, is represented by a dot of lithium and rubidium followed by a dot of cesium. Once the message is ready to send, the fuse is lit. As the flame moves through the nitrocellulose strip, each successive metallic dot burns and emits light of characteristic wavelengths. A spectrometer or camera ascertains which wavelengths are successively emitted, thereby revealing the identity and order of metals that had been placed along the strip. Currently, the signal is detectable as far as 600 meters from the fuse, Thomas says. He believes this limit could be stretched beyond 1 km. Signals of greater complexity could be encoded by utilizing other properties of light, such as intensity, he adds. No external power such as a battery or electricity is needed to encode or send messages: The metals can be dotted on the fuse by hand, and message transmission merely requires a flame. A. Prasanna de Silva, who studies molecule-based information transfer at Queen’s University of Belfast, in Northern Ireland, believes the work is significant because until now, “no such selfpowered information systems that transmit over fair distances” have been developed.—SOPHIE ROVNER
timates MDS Nordion, a pharmaceutical isotope supplier. The shutdown has left MDS and other providers of medical isotopes scrambling for additional sources. Molybdenum-99 cannot be stockpiled because of its 67-hour half-life, and it is produced by only five nuclear reactors from highly enriched uranium-235, also used to produce nuclear weapons. The other reactors are in Belgium, France, the Netherlands, and South Africa. Shortages occur when the aging facilities shut down for repairs or periodic maintenance. A leak at the Dutch reactor caused last year’s shortfall (C&EN, Sept. 15, 2008, page 7). Bill Dawes, vice president of manufacturing and supply chain at Lantheus Medical Imaging, says the intermittent outages have caused his firm to diversify its supplier relationships. The company just announced an agreement with South African isotope supplier NTP Radioisotopes. In the U.S., about 8 million procedures per year depend on the supply of isotopes from Canada, according to Robert Atcher, president of the Society of Nuclear Medicine. Longer term solutions to ensure a reliable supply of isotopes, such as using low-enriched uranium, he says, are still at the idea stage. Atcher points out that there are substitutes for many of the procedures that require technetium-99m but that they may be more expensive, more invasive, less accurate, or emit a higher dose of radiation. “The shortage means that we cannot serve the patient population as well,” he says.—MELODY VOITH
JUNE 1, 2009
