Lifestyle chemistries of phones

November 22, 2016 § Leave a comment

Swabbing a phone for chemical signatures. Credit: Amina Bouslimani and Neha Garg, UCSD

Swabbing a phone for chemical signatures.
Credit: Amina Bouslimani and Neha Garg, UCSD

It used to be that the most troubling information you could get from swabbing someone’s phone case was an abundance of E. coli indicating his or her lack of good hygiene. In a paper published in Proceedings of the National Academies of Sciences on Nov. 14, researchers at the University of California, San Diego, expanded the scope of interrogation to include a number of trace chemical signatures. The signatures can give a picture of someone’s lifestyle.

“The number of molecules detected on every object will vary depending on the surface of the object and the lifestyle of these people,” says Amina Bouslimani at UCSD. Bouslimani is a postdoctoral researcher in the laboratory of Pieter Dorrestein and the first author on the PNAS study, which was funded by the National Institute of Justice, the research arm of the U. S. Department of Justice. “For every phone, we were able to detect between hundreds and thousands of molecules or compounds,” she continues.

Bouslimani and colleagues swabbed the phones and hands of 39 volunteers. They then paired mass spectrometry with a visualization process known as molecular networking. This allowed the researchers to group similar molecules and identify unknown molecules absent from a reference database based on their similarity to known compounds.

The researchers detected a 69 percent overlap between the samples taken from participants’ hands and the backs of their phones, which demonstrated a high transferability of chemicals between the two surfaces. Among many other food items, pharmaceuticals and hygiene products, the compounds detected corresponded to citrus fruits, caffeine, antidepressants, antifungal creams, hair-loss treatments, sunscreen and mosquito-repelling DEET.

The researchers also evaluated each participant’s potential exposure to flame-retardant plasticizing agents. They posited that this analysis could be used to monitor exposure to additional environmental hazards.

While the approach is not a replacement for DNA or fingerprint analyses, Bouslimani and colleagues hope that it might fill in gaps when DNA samples are contaminated or fingerprints recovered are only partials or not in a database.

“This work is exciting and very thought-provoking,” says Glen Jackson at West Virginia University, an expert in forensic analyses by mass spectrometry.

Jackson is cautious, however, about the accuracy of linking predicted activities with mass spectrometry-confirmed exposure to chemicals.

For example, while the presence of DEET based on data analysis may be very reliable information, he says, “proving that the lifestyle, or activity level, of the suspect is camping versus gardening is a different proposition altogether.” He added that there’s more work to be done to make sure that the results of such testing aren’t misconstrued.

The strength of the approach, according to Bouslimani, is the aggregate of the individual chemical signatures. “Our work flow doesn’t just detect one unique compound on this phone,” she says. “It is the combination of many such lifestyle chemistries that will help us to understand the personal habit and lifestyle.”

Bouslimani and colleagues hope to expand the breadth of their database, which would require the efforts of outside collaborators. “It has to be now a community effort,” she says. “We really hope that other people will start to apply this technology, to take this kind of development to the next level in forensic application.”

In the meantime, Bouslimani and colleagues plan to expand the study to include 80 people and each subjects’ keys, computers and wallets.

This post was written by John Arnst, ASBMB Today’s science writer. 

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