NEWS OF THE WEEK CHEMICAL
GAS
SENSING
INTELLIGENCE INK DETECTS OXYGEN Colorimetric indicator could improve packaging security and quality control
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activated ink formulation developed by chemists in Scotland reveals the presence or absence of oxygen inside packages. The ink is blue in air and ambient room light. W h e n it is irradiated with a pulse of UV light, the color changes to white but re-
F R E S H B A C O N After UV activation, intelligence ink turns blue in air but remains colorless inside a package, indicating the absence of oxygen.
verts to blue under normal room light. In an oxygen-free atmosphere, however, the ink remains colorless after the U V pulse [Chem. Commun., published online July 9, http://xlink.rsc.org/ ?doi=10.1039/b406685e]. "Our paper reports the first example of a generic approach to chemical gas sensing in which the indicator is switched on by UV light," says chemistry professor Andrew Mills at the University of Strathclyde, Glasgow. He carried out the work with postdocs Soo-Keun Lee and Anne Lepre. "The ink is an 'intelligence ink,' HTTP://WWW.CEN-ONLINE.ORG
as it provides intelligence—that is, information—about its environment," Mills explains. "Intelligence inks are at the cutting edge of packaging, especially of foods and beverages, since they can indicate ifa package has been packed properly or tampered with or ifthe original modified atmosphere inside the package has changed." Modifled-atmosphere packaging is used extensively in the food industry. Typically, air is removed from the space above the food as it is being packed by flushing the package with an inert gas such as carbon dioxide or nitrogen. "Our ink can be readily used with packaging," Mills says. "The color change means that even an untrained eye can decide if a package is faulty" The formulation consists of four common and inexpensive in-
gredients: an aqueous dispersion of a semiconductor (TiO^, a sacrificial electron donor (triethanolamine), and aqueous solutions of a redox-indicator dye (methylene blue) and an encapsulating polymer (hydroxyethylcellulose). T h e T i 0 2 particles create electron-hole pairs when exposed to UVlight. The electrons reduce the dye, causing it to be bleached, and the holes oxidize the triethanolamine. Polymer encapsulation allows the dye to be spin-coated onto plastic, metal, paper, or other surfaces. "The ink can be reused by repeated application of UV light," Mills says. "It is just one of many we have produced for {sensing} oxygen. A variety of different color changes and sensitivities are possible." The authors note that before the ink is used in the food industry a key question will have to be addressed: Do antimicrobial or antioxidant food additives or microbial contaminants interfere with the indicator's function? The Strathclyde team is now carrying out research to answer that question. iCWe are also developing inks for other gases, such as ammonia and C0 2 ," Mills says. — MICHAEL FREEMANTLE
OBITUARY
Nobel Laureate Francis H. C. Crick, codiscoverer of the double helix structure of DNA, died last week in California. An obituary appears in C&EN Online at http:// www.cen-online.org.
BIOTECHNOLOGY
Codexis Wins $10 Million Investment From Pfizer iocatalysis and fermentation process development firm Codexis received a major boost last week with a $10 million equity investment from Pfizer. The investment accompanies a new research agreement under which the companies will focus on process R&D for Pfizer's smallmolecule drugs. Up-front payments, technology fees, and milestone payments could net Codexis an additional $40 million over the multiyear contract. Codexis will apply its MolecularBreeding protein and gene engineering technologies to develop novel process techniques for Pfizer. The drug company will have the option to acquire a nonexclusive license to certain Codexis technologies for application to its drug pipeline. Codexis, a majority-owned subsidiary of Maxygen, is already working under a previous contract with Pfizer on improving the fermentation production of doramectin, an animal parasiticide. "The deal is a massive validation for us," says Tassos Gianakakos, vice president for corporate development at Codexis. "The objective is for Pfizer to apply the technology broadly to its smallmolecule pipeline." Codexis also announced last week the commercialization of a process it designed for fine chemicals firm Lonza for making a chiral intermediate to a "major" drug. Lonza will use the Codexis process, which employs three enzymes, at its Swiss facility. Although the compound is undisclosed, Codexis recently filed a patent on an enzymatic route to 4-substituted 3-hydroxybutyric acid derivatives, intermediates used to make statin cholesterol-lowering drugs.—RICK MULLIN
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