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SCIENCE
CELL SORTER
Epithelial cell
SORTING OUT SPERM CELLS Microfluidic device could speed analysis of sexual assault evidence
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SIMPLE MICROFLUIDIC
method could substantially decrease the time required to prepare samples for forensic analysis of sexual assault evidence {Ami. Chem., 77,742 (2005)]. Faster sample preparation could help eliminate the backlog of such evi dence waiting to be analyzed. Current methods to prepare sexual assault evidence for analy sis are based on a process called differential extraction. This tech nique relies on the ability of sperm cells (from the perpetrator) to sur vive chemical conditions that rup ture the membranes of other cells (primarily epithelial cells from the victim). It is applied to the evi dence still on the cotton swab used for collection. Chemist James Ρ Landers and his coworkers at the University of DRUG
Virginia take a different approach: Sort the cells before rupturing any They have developed a microflu idic device that exploits the phys ical differences between the two types of cells to separate them. The simple device consists of two reservoirs connected by a channel. T h e epithelial cells (cheek cells in the demonstration samples) settle to the bottom of the inlet reservoir, which takes four tofiveminutes. Then, a pres sure-induced flow sweeps the sperm cells into the second reser voir. The separated cells can then go through normal DNA analysis. Landers must address a num ber of issues before the method could become practical for real forensic samples. His team is find ing that desorption of the cells from the cotton swabs could be an
A simple microfluidic device separates sperm cells from epithelial cells by allowing the epithelial cells to settle in the first reservoir and then using pressuredriven flow to sweep the sperm cells into the second reservoir.
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issue. In addition, because cells can rupture while the samples are dry during storage, free D N A in the samples could be another concern, which may have to be addressed by chromatography Susan Greenspoon, a forensic molecular biologist with the Virginia Division of Forensic Science, says that "the device is not yet up to the level of performance we can obtain using either semiautomated robotic or manual differential extraction." But she believes that, with further development, it "has real potential to supplant our current methods."—CELIA HENRY
RESEARCH
Oxidized Anion May Have Role In Yioxx Toxicity
O
xidation to a maleic anhydride may be a factor in the long-term toxicity of rofecoxib (Vioxx), a new report suggests. This reactivity is not shared by other cyclooxygenase-2 (C0X-2) inhibitors. The hypothesis, if proven true, runs counter to the assumption that other C0X-2 inhibitors pose the same risk as Vioxx. Vioxx, a painkiller, was withdrawn from the market last September by its manufacturer, Merck, after a clinical trial indicated that it poses an increased risk of cardiovascular problems. Vioxx is a weak acid, and its anion is highly reactive toward
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atmospheric oxygen, according to laboratory studies by Harvard University chemists Leleti Rajender Reddy and E. J. Corey. The products are principally a maleic anhydride and a lesser amount of a γ-hydroxybutenolide [Tetrahedron Lett, published online Dec. 25, 2004, http://dx. doi.org/l 0.1016/j.tetlet.2004.12. 055]. The maleic anhydride had not been reported as a Vioxx metabolite. The authors sug gest that some of it may survive long enough in vivo to react with biomolecules and tissues. "The consequences of this may be a low-level chronic toxicity that is
cumulative and possibly dan gerous over periods of many months," they write. Merck's withdrawal of Vioxx has cast doubts on other COX-2 inhibitors. However, formation of a reactive anion is unique to Vioxx, the authors point out. The difference in reactivity of Vioxx and other COX-2 in hibitors has been "overlooked in the medical and general lit erature," they write. The authors have disclosed their findings to FDA. Corey is a scientific adviser to Pfizer, the maker of the COX-2 inhibitors Celebrex and Bextra.—MAU REEN ROUHI
IN] BRIEF: STRIKEFORÇE An artist's conception depicts NASA's Deep Impact spacecraft just after a deployed "impactor" strikes the nucleus of comet Tempel 1. The debris kicked up by the impact may help reveal the comet's structure. Successfully launched on Jan. 12, Deep Impact is on a six-month journey to the comet.
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