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Fingerprints reveal drug habits An assay detects drug metabolites excreted in sweat from the hands.
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spire more. “We’ve also gotten fingerhandling paper money, for example hat if a criminal’s fingerprints (Anal. Chem. 2000, 72, 397 A–403 A). prints from people who cycle or run to could reveal whether he or she work, and it hasn’t impacted the quality The investigators want to catch drug indulges in a certain drug as well as of the fingerprints. The more somebody abusers. “If we go for the metabolite, make his or her identity known? David then we know the person is a user,” says sweats, the better,” says Russell. Russell and colleagues at the University Russell says that he and his co-workRussell. of East Anglia and King’s College Loners are doing several things to make the Russell and colleagues modified gold don (both in the U.K.) have developed assay more amenable to fieldwork. Innanoparticles with an antibody that has a way to visualize drug metabolites in addition to the unique swirls and whorls a strong affinity for cotinine. They asked stead of adding a secondary antibody with a fluorescent tag in fingerprints (Angew. to the modified nanoChem., Int. Ed. 2007, (a) (b) (c) particles, the investi46, 4100– 4103). gators are trying to Skin on the palms fluorescently tag the and fingers has ridges primary antibodies on and grooves that prothe nanoparticles to duce fingerprints, and reduce the number of each skin ridge has a steps in the procedure. row of pores through They are also working which sweat is excreted. on ways to make the Sweat contains all kinds assay capable of deof substances, including tecting multiple analactate, urea, amino lytes, either by incoracids, and metabolites of Fluorescence images, at various magnifications, show detailed fingerprint information. The images come from the thumb of a male smoker after 40 minutes of sweatporating several types ingested drugs. When a of antibodies on every finger touches a surface, ing. Scale bars: (a) 5, (b) 2, and (c) 1 mm. (Adapted with permission. Copyright 2007 nanoparticle or by desweat is transferred from Wiley-VCH Verlag GmbH & Co KGaA.) veloping a mixture of the skin to the surface volunteers to first wash their hands and nanoparticles each modified with a difand leaves an impression of the finger’s then place a hand inside a wrapped ferent antibody. ridge pattern. This is called a latent, or glass beaker to induce sweating. After Russell and colleagues are working invisible, fingerprint that can be seen closely with the police. They also are only after physical or chemical treatment. some time, the volunteers were asked considering other applications, such as The investigators developed a chemi- to hold a clean glass slide to create fingerprints. Next, the researchers deposit- workplace screening and drug testing cal treatment to visualize drug metaboed the modified nanoparticles on the for sports. “We had a soccer competilites in fingerprint sweat. They based glass slide. After an incubation period, tion, and the guy nominated to give the their assay on cotinine, a metabolite of secondary fluorescently labeled anti[drug test] sample had to wait for hours nicotine. Russell says the investigators body fragments were added to the slide. because he was so dehydrated, he was went after smokers because, “We needAfter a washing step, the investigators unable to produce a urine sample,” says ed to show proof of principle because Russell. “Now we can easily do an analviewed the slide under a fluorescence the long-term goal is to do narcotics ysis very quickly.” A key aspect in sports microscope. and drugs of abuse. We needed somedrug testing is to make sure a sample is They found that the modified nanothing for which we could readily get the correctly attributed to an athlete—curparticles clearly distinguished between student body to provide fingerprints smokers and nonsmokers—the smokers’ rent sampling methods in sports involve and do so quite happily. Asking ‘Are fingerprints glowed with the fluorescent a convoluted coding and chain-of-cusyou on heroin or cocaine?’ wouldn’t tody system. But with the method deantibodies, but the nonsmokers’ fingerget us many volunteers!” veloped by Russell and colleagues, he prints didn’t give any signals. Among Russell and colleagues didn’t want says, “you’ve got the identification and smokers, fingerprints obtained from to detect unadulterated drugs, because men gave stronger signals than those the analysis all in the same sample.” a these can end up on people’s hands in from women, because men tend to per—Rajendrani Mukhopadhyay the most innocuous of ways—just from © 2007 AMERICAN CHEMICAL SOCIETY
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