Tag Archives: Gabriela Valdés-Ramírez

Monitoring your saliva via mouth guard and smart phone

I first came across the notion that saliva instead of blood and urine could be used to assess and monitor health in a presentation abstract for the 2004 American Association for the Advancement of Science (AAAS) annual meeting held in Seattle, Washington (as per my Feb. 15, 2011 posting). There have been a few ‘saliva’ health monitoring projects mentioned here over the years but this proof-of-concept version seems like it has the potential to get to the marketplace. An August 31, 2015 news item on Nanowerk features a ‘saliva’ health monitoring project from the University of California at San Diego (UCSD),

Engineers at the University of California, San Diego, have developed a mouth guard that can monitor health markers, such as lactate, cortisol and uric acid, in saliva and transmit the information wirelessly to a smart phone, laptop or tablet.
The technology, which is at a proof-of-concept stage, could be used to monitor patients continuously without invasive procedures, as well as to monitor athletes’ performance or stress levels in soldiers and pilots. In this study, engineers focused on uric acid, which is a marker related to diabetes and to gout. Currently, the only way to monitor the levels of uric acid in a patient is to draw blood.

An August 31, 2015 UCSD news release (also on EurekAlert), which originated the news item, describes the research and the mouth guard in more detail,

In this study, researchers showed that the mouth guard sensor could offer an easy and reliable way to monitor uric acid levels. The mouth guard has been tested with human saliva but hasn’t been tested in a person’s mouth.

Researchers collected saliva samples from healthy volunteers and spread them on the sensor, which produced readings in a normal range. Next, they collected saliva from a patient who suffers from hyperuricemia, a condition characterized by an excess of uric acid in the blood. The sensor detected more than four times as much uric acid in the patient’s saliva than in the healthy volunteers.

The patient also took Allopurinol, which had been prescribed by a physician to treat their condition. Researchers were able to document a drop in the levels of uric acid over four or five days as the medication took effect. In the past, the patient would have needed blood draws to monitor levels and relied instead on symptoms to start and stop his medication.

Fabrication and design

Wang’s team created a screen-printed sensor using silver, Prussian blue ink and uricase, an enzyme that reacts with uric acid. Because saliva is extremely complex and contains many different biomarkers, researchers needed to make sure that the sensors only reacted with the uric acid. Nanoengineers set up the chemical equivalent of a two-step authentication system. The first step is a series of chemical keyholes, which ensures that only the smallest biochemicals get inside the sensor. The second step is a layer of uricase trapped in polymers, which reacts selectively with uric acid. The reaction between acid and enzyme generates hydrogen peroxide, which is detected by the Prussian blue ink.  That information is then transmitted to an electronic board as electrical signals via metallic strips that are part of the sensor.

The electronic board, developed by Mercier’s team, uses small chips that sense the output of the sensors, digitizes this output and then wirelessly transmits data to a smart phone, tablet or laptop. The entire electronic board occupies an area slightly larger than a U.S. penny.

Next steps

The next step is to embed all the electronics inside the mouth guard so that it can actually be worn. Researchers also will have to test the materials used for the sensors and electronics to make sure that they are indeed completely biocompatible. The next iteration of the mouth guard is about a year out, Mercier estimates.

“All the components are there,” he said. “It’s just a matter of refining the device and working on its stability.”

Wang and Mercier lead the Center for Wearable Sensors at UC San Diego, which has made a series of breakthroughs in the field, including temporary tattoos that monitor glucose, ultra-miniaturized energy-processing chips and pens filled with high-tech inks for Do It Yourself chemical sensors.

Here’s a link to and a citation for the paper,

Wearable salivary uric acid mouthguard biosensor with integrated wireless electronics by Jayoung Kim, Somayeh Imani, William R. de Araujo, Julian Warchall, Gabriela Valdés-Ramírez, Thiago R.L.C. Paixão, Patrick P. Mercier, & Joseph Wang. Biosensors and Bioelectronics Volume 74, 15 December 2015, Pages 1061–1068 doi:10.1016/j.bios.2015.07.039

This paper is behind a paywall.

Here’s an image of UCSD’s proposed mouth guard,

The mouth guard sensor offers an easy and reliable way to monitor uric acid levels in human saliva. Credit: Jacobs School of Engineering, UC San Diego

The mouth guard sensor offers an easy and reliable way to monitor uric acid levels in human saliva. Credit: Jacobs School of Engineering, UC San Diego

University of Toronto’s (Canada) smiley face tattoo/sensor

Researchers at the University of Toronto have created a medical sensor that can be applied to the skin like a temporary tattoo.

University of Toronto Scarborough student Vinci Hung helped create the smiley face sensor shown here in the box at upper right (photo by Ken Jones)

The Dec. 3, 2012 news item on ScienceDaily notes,

A medical sensor that attaches to the skin like a temporary tattoo could make it easier for doctors to detect metabolic problems in patients and for coaches to fine-tune athletes’ training routines. And the entire sensor comes in a thin, flexible package shaped like a smiley face.

“We wanted a design that could conceal the electrodes,” says Vinci Hung, a PhD candidate in the Department of Physical & Environmental Sciences at UTSC [University of Toronto Scarborough], who helped create the new sensor. “We also wanted to showcase the variety of designs that can be accomplished with this fabrication technique.”

The Dec. 3, 2012 University of Toronto news release by Kurt Kleiner, which originated the news item, provides details about how the sensor/tattoo is fabricated and how it functions on the skin,

The new tattoo-based solid-contact ion-selective electrode (ISE) is made using standard screen printing techniques and commercially available transfer tattoo paper, the same kind of paper that usually carries tattoos of Spiderman or Disney princesses. In the case of the smiley face sensor, the “eyes” function as the working and reference electrodes, and the “ears” are contacts to which a measurement device can connect.

The sensor Hung helped make can detect changes in the skin’s pH levels in response to metabolic stress from exertion. Similar devices, called ion-selective electrodes (ISEs), are already used by medical researchers and athletic trainers. They can give clues to underlying metabolic diseases such as Addison’s disease, or simply signal whether an athlete is fatigued or dehydrated during training. The devices are also useful in the cosmetics industry for monitoring skin secretions.

But existing devices can be bulky, or hard to keep adhered to sweating skin. The new tattoo-based sensor stayed in place during tests, and continued to work even when the people wearing them were exercising and sweating extensively. The tattoos were applied in a similar way to regular transfer tattoos, right down to using a paper towel soaked in warm water to remove the base paper.

To make the sensors, Hung and her colleagues used a standard screen printer to lay down consecutive layers of silver, carbon fibre-modified carbon and insulator inks, followed by electropolymerization of aniline to complete the sensing surface.

By using different sensing materials, the tattoos can also be modified to detect other components of sweat, such as sodium, potassium or magnesium, all of which are of potential interest to researchers in medicine and cosmetology.

You can find the reserchers’ article in the Royal Society’s Analyst journal,

Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring
Amay J. Bandodkar ,  Vinci W. S. Hung ,  Wenzhao Jia ,  Gabriela Valdés-Ramírez ,  Joshua R. Windmiller ,  Alexandra G. Martinez ,  Julian Ramírez ,  Garrett Chan ,  Kagan Kerman and Joseph Wang in Analyst, 2013,138, 123-128 DOI: 10.1039/C2AN36422K

The article is open access but you do need to register for a free account with the Royal Society’s RSC [ublishing platform.