A fingerprint is of no use to an investigator unless it can be matched to one in a database or can be directly compared with that of a suspect. Russell and his team expect that we will soon be able to gain information about the lifestyle of the person who made the fingerprints, which could shrink the pool of suspects. In this way, it should be possible to use fingerprints to detect drugs, medications, or food that have been consumed, and also to diagnose some diseases.
Researchers want to coax all of these secrets out of the tiny traces of perspiration that a fingerprint leaves on a surface. The research team demonstrated the ease with which this should be possible by differentiating between fingerprints made by smokers and nonsmokers. To avoid false results from chance contact with tobacco products, they designed their system to detect cotinine, a metabolite formed by the body after consumption of nicotine. Applying nanotechnology, the researchers wet the fingerprints with a solution containing gold nanoparticles to which cotinine-specific antibodies were attached. These bind to the cotinine. Subsequently, a second antibody, which was tagged with a fluorescent dye and binds specifically to cotinine antibodies, was applied to the fingerprint. Because there are many cotinine antibodies attached to each nanosphere, there is a significant amplification effect.
Indeed, the ridge patterns of smokers’ fingerprints fluoresce, while those of nonsmokers do not. The fingerprints are very highly resolved and can be lifted for comparison with known prints, just as in conventional procedures. When magnified, even the tiny sweat pores along the ridges of the fingertip become visible, which can also be used to make an unambiguous assignment.
In addition to forensic applications, this method would be ideal for detecting doping. Sample manipulations by the test subjects would hardly be possible since each sample is uniquely assignable to a specific athlete by virtue of the ridge pattern. Medical diagnostics could also benefit in the form of simple and quick mass screening with no danger of sample mix-ups. Another application could be drug screening without taking blood samples—from suspicious drivers, for example.