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MATERIALS SCIENCE: Tannic acid and Fe(III) form a one-pot, self-assembling coating for any shaped object
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thought of it first.” OH “The coating’s pH senO O sitivity is the really exciting O O OH aspect,” comments Phillip B. O O HO O Messersmith, a biomedical OH O O engineer at Northwestern O HO O O University. The coating forms O above pH 6, but in more HO acidic environments it O falls apart, revealing HO HO OH or releasing the conOH O HO tents of objects within HO O OH it. One could envision O using the coating as a way to deliver a drug to a cell’s acidic lysosome or endosome HO and then having the contents released in the organelle’s low-pH environment, he says. OH HO Researchers use “tannic acid” to describe a Tannic acid family of molecules that contain a central glucose with one to five polygalloyl groups of varying lengths that emanate from the sugar base. Every Fe(III) atom can coordinate three pairs of hydroxyl groups found on tannic acid and thus can complex up to three different tannic acid molecules. Meanwhile, the abundance of hydroxyl groups in tannic acid means that each tannic acid molecule can complex up to a dozen or so iron atoms. The result is a cross-linked coating that is about 10 nm thick, Caruso says. The technique seems like it could be easily expanded, Bielawski says. “There are a lot of other polyphenols out there besides tannic acid, so there’s considerTannic acid and iron combine able potential for changing the surface to form a coating on polystyrene chemistries of the coating and creating substrates as shown by atomic new applications.”—SARAH EVERTS force microscopy. O
SIMPLE, SAFE, AND CHEAP COATING
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to prevent cavities coated their teeth with black solutions of iron mixed with vegetable tannins. This custom of ohaguro was abandoned by the Japanese in the 19th century, but chemists in Australia have resurrected a version of the technique with potential applications far beyond preventive dentistry. A team led by Frank Caruso at the University of Melbourne has developed a simple one-pot recipe for a coating made of only Fe(III) and tannic acid, a polyphenol found in wood that is perhaps best known for improving the flavor of wood-casket-aged red wine. The coating is unusually versatile. It can cover all manner of nano- and microscopic objects, including gold nanoparticles, calcium carbonate and silicon dioxide particles, and bacteria, regardless of whether the object to be coated is positively charged, negatively charged, or neutral (Science 2013, DOI: 10.1126/science.1237265). The discovery is patentpending. Since both Fe(III) and tannic acid are generally regarded as safe by regulators and are already used in food and biomedical applications, the coating could find uses right away in areas as diverse as drug delivery and corrosion protection, comments Christopher W. Bielawski, a chemist at the University of Texas, Austin. “This is going to make a big impact mainly because it is so simple,” he adds. “Many will wish that they had
OUTSOURCING Contract research firm Evotec to close chemistry labs in India In a reversal of the trend of moving pharmaceutical chemistry research to Asia, the drug discovery services firm Evotec has decided to close its laboratories in Thane, India, and conduct all chemistry research in Abingdon, England, instead. Evotec didn’t encounter performance or quality problems with the Indian staff, says Evotec Chief Operating Officer Mario Polywka. “They are the most amazing organic chemists.” Rather, Polywka says, the firm’s increasing focus on high-value collaborations—including with Harvard University and the Belfer Institute for Applied Can-
cer Science—means that close involvement by the firm’s medicinal chemists with research partners is paramount. The Indian labs’ operations will wind down by the end of September, Evotec says, putting 120 people out of work. Employment in Abingdon, where about 180 medicinal and other chemists work now, will increase, Polywka adds, although he won’t give a number. Germany-based Evotec acquired the Thane operation, Research Support International, in 2009 as part of a bid to create a low-cost Asian operation. But more recently, customers have been requesting Europe-based services,
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Polywka says. In addition, Evotec had to relocate the Indian labs by June 2014 and was unable to find a comparable site, he says. Indian contract chemistry firms such as GVK Bio, TCG Lifesciences, and Syngene continue to grow, says Nailesh A. Bhatt, an India expert who heads the Princeton, N.J.-based strategic advisory firm Proximare. But non-Indian companies often underestimate the complexities of integrating and operating an Indian acquisition, he notes, especially if the local promoter is no longer involved, as was the case with Research Support International.—MICHAEL MCCOY
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N ANCIENT JAPANESE culture, those who wished
