NEWS OF THE WEEK ACS M E E T I N G NEWS
NONINVASIVE GLUCOSE DETECTION
the sensor yet with patients, so Hernandez isn't sure whether they will need to be induced to cry. He and his students joke about needing to use something that smells like onions. The method is already sensi-
SMALL SCALE Garcia (left) and Hernandez use gold nanoparticles to measure glucose at very low concentrations.
Gold nanoparticle method detects glucose at the low levels found in healthy people
U
SING GOLD NANOPARTICLES,
researchers at the University ofCentral Florida in Orlando can noninvasively detect low levels of glucose in human tears. "The detection limit is low enough to detect levels of glucose in healthy persons," chemistry professor Florencio Hernandez told C&EN. "The idea is to use this method to determine glucose concentrations at very early stages. You can actually detect potential diabetic problems before diabetes becomes a problem." When glucose is in solution, some of it is present in the openchain aldehyde form. Hernandez, graduate student Marisol Garcia, and coworkers use gold nanoparticles to detect glucose with a test—based on the familiar Tollen's silver mirror test for aldehydes—in which they detect the aldehyde through a reaction with chloroauric acid. They described their work in a poster session last week sponsored by the Division of Analytical Chemistry at the ACS national meeting in Atlanta. Hernandez expected the glucose detection to work just like a mercury sensor his team had made previously. In that case, gold nanorods were suspended in a gpld salt solution. When mercury is added to the solution, the mercury and goldforman amalgam that changes the effective length of the nanorods and shifts one of the surface plasmon resonance bands in the absorbance spectrum. The mercury test is sensitive to concentrations as low as parts per quadrillion. The glucose sensor, however, didn't behave in the same way. "There were some interferences from gluconic acid, which stabiWWW.CEN-0NLINE.ORG
lizes metal nanoparticles," Hernandez said. "You start generating nanospheres instead of growing the nanorods." As more nanospheres form, a spectral feature known as the extinction efficiency changes proportionally to the glucose concentration. The researchers measure the absorbance spectrum with a small UV-Vis spectrometer from Ocean Optics. The best fluid for doing the test is tears, Hernandez said. The glucose concentration in tears is known to correlate with the blood glucose concentration. "We're thinking about how many drops of tears we're going to need," he said. "We hope that a couple of tears will be more than enough to determine the concentration." The number of tears necessary will depend on the glucose concentration. The researchers haven't used
tive enough to detect glucose in healthy individuals, but Hernandez wants to drive the sensitivity even lower, so that he can use the method to monitor the effects of diet on glucose levels in healthy people. In addition, contrary to other tests that measure glucose, this method is truly noninvasive. Even the methods that use contact lenses are "pseudoinvasive," Hernandez said. He sees the method as a tool for both researchers and patients.—CELIA ARNAUD
EUROPEAN INDUSTRY
Wacker Outlines Plan For Public Stock Offer
W
acker Chemie executives have embarked on an international road show to talk up their company with investors prior to an April 10 stock offering on the Frankfurt Securities Exchange. The family-owned company's goal for the initial public offering (IPO) is to sell about 25% of its shares, raising at least $300 million. The Wacker family will continue to hold just under 56% of Wacker Chemie, which had sales of $3.44 billion in 2005, up 10% over 2004. The planned share sale comes less than a year after the Wacker family regained full ownership of the firm by buying out the 44% stake held by Sanof i-Aventis. Wacker Chemie then converted itself into a stock corporation in December in anticipation of an IPO. The money being raised will help the compa-
ny expand in a variety of business areas. Wacker Chemie, for example, is in the process of expanding its capacity for silicones in Chinsf; building a new polysilicone plant in Burghausen, Germany; and expanding capacity for 300-mm silicon wafers in its Siltronic unit at Burghausen and at Freiberg, also in Germany. "The initial public offer is a milestone in the history of Wacker going back over 90 years," says Peter-Alexander Wacker, head of the management board. "Through access to the capital market, we shall be better able to use the opportunities for growth before us." In 2003, the company contemplated an IPO of just the Siltronic unit. The plan was scrapped, however, partly because of the business' bad financial performance in 2004 (C&EN, May 9,2005, page 15).-PATRICIA SHORT C & E N / A P R I L 3, 2006
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