HÉffiiteteFTHÈWiEIÎ NANOTECHNOLOGY
DEVELOPED FOR DETECTION Silver-coated gold nanoparticles provide sensitive DNA Raman assay
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OMBINING NANOPARTICLES
decorated with dye molecules and surface-enhanced Raman spectroscopy (SERS) provides a sensitive D N A assay, according to chemists at Northwestern University Previously, chemistry professor Chad A. Mirkin's group had developed a scanometric assay in which gold nanoparticles are functionalized with probe oligonucleotide strands that are complementary to a sequence in a target strand of D N A [Science, 289,1757 (2000)].Theprobe and target are captured by a D N A strand on a microchip array, which is "developed" by plating silver on it. Now, they show that the silver can act as a SERS enhancer. Mirkin, postdoc YiinWei Charles Cao, and graduate student Rongchao Jin show that the sensitivity of the SERS assay is 20 femtomolar— a detection limit that isn't even close to being optimized, Mirkin says [Science, 297,1536 (2002)}. In addition, the Raman dyes provide easily distinguishable spectroscopic fingerprints with very narrow bandwidths, an advantage over fluorescence. Mirkin and his coworkers used the Raman-active dyes to demonstrate that they could distinguish between dissimilar D N A targets from a variety ofviruses and bacteria. The Raman spectra indicated that the assay was selective with no cross-hybridization. Mirkin says his group is "turning the SERS approach upside down. Most people try to create a SERS active substrate and do chemistry on top of it. The probHTTP://PUBS.ACS.ORG/CEN
lem is that the substrate changes over time. Here you're always reading right after the developing." Chemistry professor Richard P. Van Duyne, also at N o r t h western, is one of the discoverers of the SERS effect. "The ondemand creation of the silver surface circumvents the old problem of limited stability and reproducibility that had previously been a serious limitation to the practical application of SERS and related techniques," he says. Shuming Nie, professor of biomedical engineering and chemistry at Georgia Tech and Emory University, says, 'After 25 years and more than 4,000 papers, the phenomenon of surface Raman enhancement is finally becoming a useful method for chemical and biological studies."
Mirkin anticipates a time when nanoparticle-based detection will supplant molecular fluorescence. "The argument has been made in almost every category—sensitivity selectivity, ease of use, flexibility, and cost—for the replacement of molecular fluorophore technology with nanoparticle-based technology," he says. He would like to see this technology eventually make it to the doctor's office. The nanoparticle SERS assay has been licensed by Nanosphere Inc., a Northbrook, 111., company that Mirkin cofounded.—
ENHANCING From left: Mirkin, Jin, and Cao.
CELIA HENRY
OUTREACH
Biogen Sets Aside Space And Resources For Community Laboratory
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iogen has opened an 1,110-sq-ft teaching facility at its headquarters site in Cambridge, Mass. The Community Laboratory, as it's called, was designed to serve Cambridge public school students. The biopharmaceutical company worked closely with the city and school system in its development. The lab will offer "exciting educational opportunities and provide students with a glimpse of how science can be applied to careers in biotechnology," Biogen Chairman and CEO James C. Mullen says. "We look forward to continuing to work together to ensure it remains a resource that supports the work being done in classrooms and aids in the development of future scientists."
The laboratory space is within one of Biogen's R&D buildings and is outfitted with the latest equipment and technology. This summer, nearly 50 Cambridge Rindge & Latin School 11th- and 12th-grade students enrolled in two one-week sessions on molecular genetics. Experiments included the extraction of DNA from living cells and the purification of proteins from bacteria. Biogen scientists led discussions on technology and applications to discover and develop new therapeutics. During the school year, classes will visit the lab to conduct experiments. The company anticipates using the lab for employee and adult education programs as well.—ANN THAYER
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