University of
California San Diego Health Sciences
We leave behind trace
chemicals, molecules and microbes on every object we touch.
By sampling the
molecules on cell phones, researchers at University of California San Diego
School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences
were able to construct lifestyle sketches for each phone's owner, including
diet, preferred hygiene products, health status and locations visited.
This proof-of-concept
study, published November 14 by Proceedings of the National Academy of
Sciences, could have a number of applications, including criminal
profiling, airport screening, medication adherence monitoring, clinical trial
participant stratification and environmental exposure studies.
"You can imagine
a scenario where a crime scene investigator comes across a personal object --
like a phone, pen or key -- without fingerprints or DNA, or with prints or DNA
not found in the database.
They would have nothing to go on to determine who that belongs to," said senior author Pieter Dorrestein, PhD, professor in UC San Diego School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences. "So we thought -- what if we take advantage of left-behind skin chemistry to tell us what kind of lifestyle this person has?"
In a 2015 study,
Dorrestein's team constructed 3D models to illustrate the molecules and
microbes found at hundreds of locations on the bodies of two healthy adult
volunteers. Despite a three-day moratorium on personal hygiene products before
the samples were collected, the researchers were surprised to find that the
most abundant molecular features in the skin swabs still came from hygiene and
beauty products, such as sunscreen.
"All of these
chemical traces on our bodies can transfer to objects," Dorrestein said.
"So we realized we could probably come up with a profile of a person's
lifestyle based on chemistries we can detect on objects they frequently
use."
Thirty-nine healthy
adult volunteers participated in Dorrestein's latest study. The team swabbed
four spots on each person's cell phone -- an object we tend to spend a lot of
time touching -- and eight spots on each person's right hand, for a total of
nearly 500 samples.
Then they used a technique called mass spectrometry to
detect molecules from the samples. They identified as many molecules as
possible by comparing them to reference structures in the GNPS database, a
crowdsourced mass spectrometry knowledge repository and annotation website
developed by Dorrestein and co-author Nuno Bandeira, PhD, associate professor
at the Jacobs School of Engineering and Skaggs School of Pharmacy and
Pharmaceutical Sciences at UC San Diego.
With this information,
the researchers developed a personalized lifestyle "read-out" from
each phone.
Some of the
medications they detected on phones included anti-inflammatory and anti-fungal
skin creams, hair loss treatments, anti-depressants and eye drops.
Food molecules
included citrus, caffeine, herbs and spices.
Sunscreen ingredients
and DEET mosquito repellant were detected on phones even months after they had
last been used by the phone owners, suggesting these objects can provide
long-term composite lifestyle sketches.
"By analyzing the
molecules they've left behind on their phones, we could tell if a person is
likely female, uses high-end cosmetics, dyes her hair, drinks coffee, prefers
beer over wine, likes spicy food, is being treated for depression, wears
sunscreen and bug spray -- and therefore likely spends a lot of time outdoors
-- all kinds of things," said first author Amina Bouslimani, PhD, an
assistant project scientist in Dorrestein's lab.
"This is the kind
of information that could help an investigator narrow down the search for an
object's owner."
There are limitations,
Dorrestein said.
First of all, these
molecular read-outs provide a general profile of person's lifestyle, but they
are not meant to be a one-to-one match, like a fingerprint.
To develop more
precise profiles and for this method to be more useful, he said more molecules
are needed in the reference database, particularly for the most common foods
people eat, clothing materials, carpets, wall paints and anything else people
come into contact with.
He'd like to see a trace molecule database on
the scale of the fingerprint database, but it's a large-scale effort that no
single lab will be able to do alone.
Moving forward,
Dorrestein and Bouslimani have already begun extending their study with an
additional 80 people and samples from other personal objects, such as wallets
and keys.
They also hope to soon
begin gathering another layer of information from each sample -- identities of
the many bacteria and other microbes that cover our skin and objects.
In a 2010 study, their
collaborator and co-author, Rob Knight, PhD, professor in the UC San Diego
School of Medicine and Jacobs School of Engineering and director of the Center
for Microbiome Innovation at UC San Diego, contributed to a study in which his
team found they could usually match a computer keyboard to its owner just based
on the unique populations of microbes the person left on it.
At that time, they
could make the match with a fair amount of accuracy, though not yet precisely
enough for use in an investigation.
Beyond forensics,
Dorrestein and Bouslimani imagine trace molecular read-outs could also be used
in medical and environmental studies.
For example, perhaps
one day physicians could assess how well a patient is sticking with a
medication regimen by monitoring metabolites on his or her skin.
Similarly, patients
participating in a clinical trial could be divided into subgroups based on how
they metabolize the medication under investigation, as revealed by skin
metabolites -- then the medication could be given only to those patients who
can metabolize it appropriately.
Skin molecule
read-outs might also provide useful information about a person's exposure to
environmental pollutants and chemical hazards, such as in a high-risk workplace
or a community living near a potential pollution source.