Chemical "traces" on the phone can tell about the life of the owner

We reserve traces of chemicals, molecules and microbes on each item we touch. Collecting molecular samples on smartphones, researchers from the University of California School of Medicine and the Skaggs School of Pharmacy and Pharmaceutical Sciences were able to model the wearer's lifestyle, including diet, hygiene products that he uses, his health and frequently visited places. The results of the study could be used for forensic examination, airport screening, monitoring treatment adherence, stratification of participants for clinical trials and environmental impact studies.



Imagine a situation where an investigator finds a personal object at a crime scene, such as a phone, pen or key without fingerprints or DNA. Or there are traces, but they were not found in the database. The investigators have nothing to determine to whom this thing belongs. The lead author of the study, Peter Dorstein, Ph.D. from the University of California School of Medicine, asked himself: "What if we conduct a chemical analysis of traces from the surface of devices that a person often uses to create a" portrait "of his lifestyle?"

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Last year , the Dorshtein team built 3D models illustrating molecules and microbes that were found in hundreds of places on the body of two adult volunteers. For three days, the subjects ignored personal care products before the researchers took samples. Despite this, scientists have found traces of sunscreen and other cosmetic products in skin samples.



The person transfers these traces to any other physical objects. Thus, scientists came to the conclusion that they could probably create a profile of a person’s life based on chemical “imprints” that remain on frequently used objects.





The main stages of the experiment



This experiment involved 39 adult volunteers. A team of scientists took samples from four points of the smartphone and eight points of the human right hand: a total of about 500 samples. They then used mass spectrometry to isolate individual molecules from samples. The Dorshtein group tried to find as many molecules as possible by comparing them with samples from several databases.



With this information, researchers have developed a personalized “reader” lifestyle with each smartphone. Some devices have found traces of drugs, hair loss medicines, antidepressants, and eye drops. Molecules of food products - citrus, caffeine, herbs and spices. Sunscreens and mosquito repellents were found on the phones months after the device owner had used them for the last time. The Dorshtein Group believes that such tools can provide a more detailed "identikit" of life.





A map showing the localization and concentration of molecules of interest on the hands and phones of four participants in the experiment



The result of the analysis is detailed. A typical example looks like this: “a woman uses quality cosmetics, dyes her hair, drinks coffee, prefers beer to wine, likes spicy food, is treated for depression and uses sunblock and insect repellent, spends a lot of time outdoors.” According to Amina Buslimani, a candidate of medical sciences and co-author of the work, this information will help the investigator to narrow down the search for the owner of the subject.



Dorstein notes that this technique has several limitations. "Reading" the molecules at the exit gives only a general idea of ​​a person's lifestyle. This method is not intended to be an alternative to fingerprints. To develop accurate "portraits" that can be useful for the investigation, we need a more complete database of molecules. In particular, the most common food, clothing, carpets, paints for walls and everything that people constantly come into contact with. He would like to create a database comparable in scale to the fingerprint databases. However, this will require serious efforts, and no laboratory can do it alone.



Contrary to restrictions, the Dorshtein team expanded its research to 80 people. This time, scientists collected other personal items, such as wallets and keys. They hope in the near future to begin collecting another layer of information from each sample - the belonging of certain bacteria and microbes to a specific person. In a 2010 study, their associate and co-author Rob Knight and his team found that to establish compliance, it is enough to detect a unique microbial population. Then you can hold the thread from the object to the owner with a fair amount of accuracy. For use in investigations, it was still not enough.



Melanie Bailey, an expert in forensic medicine at the University of Surrey, believes that the approach of the Dorshtein team can be valuable: "Information obtained in this way will narrow the list of suspects or give at least some hint at what person you need to work further on .



But John Bond, the former head of the Northamptonshire Police Forensic Service and professor of criminology at the University of Leicester , is less optimistic. He pointed out that it is already possible to detect traces of firearms, explosives, and drug trafficking at sites. He does not understand how lifestyle-related chemicals will help “cover” a criminal: “The problem is that they are not very picky about these things. If you find traces of a particular brand of cosmetics, this is unlikely to really help narrow the search and will be what you really need. ”



In addition to forensic analysis, Dorstein and Buslimani consider their technology suitable for medical and environmental studies. One day, doctors would be able to assess how well a patient follows a course of treatment, following the metabolic products on his skin. Patients participating in the clinical trials of a drug can be divided into subgroups based on skin metabolites. Then medications can be given to those patients who will assimilate them properly. Reading traces on the skin will provide useful information about the effects of environmental pollutants or chemical factors on humans.



Scientific work published in the journal Proceedings of the National Academy of Sciences November 14, 2016

DOI: 10.1073 / pnas.1000162107