Analyst http://dx.doi.org/10.1039/c1an15200a (2011)

DNA profiling is widely used by forensic investigators to identify an offender from just a single cell. However, equally valuable is the ability to detect and identify traces of body fluids such as saliva, semen and blood on various objects at the crime scene. At present, methods and tests used to analyse body fluids are destructive and have a low specificity. Now, Nunzianda Frascione and colleagues at King's College London have shown that magnetic nanoparticles conjugated with specific antibodies can detect and identify blood and saliva in situ on different types of substrates.

The researchers functionalized magnetic nanoparticles with fluorescently labelled antibodies that recognize specific components of red blood cells, white blood cells or saliva. They applied the nanoparticles to human blood or saliva that had been smeared onto a glass slide. After 30 mins the unbound nanoparticles were removed by a magnet and the bound conjugates were visualized under a fluorescent microscope. The antibodies showed good specificity and had little cross reactivity with other body fluids. Furthermore, blood stains that were treated with the nanoparticles could still be used for DNA profiling, suggesting that this method could potentially save money as DNA profiling would only be carried out on identified sections of the samples. The method also worked on samples on substrates such as ceramic, paper and dark fabrics, thereby increasing the likelihood of uncovering important evidence at the crime scene.