Do sweat- and blood- monitoring open a new window on future medical care!?

A biosensor that can easily measure body components

By quantifying body information, we measure our health and think about improving our lifestyle. For example, the most familiar factors include weight, body temperature, and blood pressure. These are typical examples of physical information about the body.

In addition, blood tests can reveal blood sugar levels, gamma-GTP, and cholesterol levels. These are information on components of the body.

Some devices that measure physical information are now very familiar, such as weight scales and thermometers, and can be easily used by individuals at home.

On the other hand, we normally obtain information on components of our body by having a blood test at a medical institution which takes a few days to get a result.

Therefore, we are striving to develop a device that can also easily handle information on body components like one that handles physical information.

The best way to investigate information on components of the body is to measure blood components. However, in order to do so, a physical invasion by piercing the skin and blood vessel is required to collect blood. This is not something that can be easily done by anyone.

For this reason, substances that are easier to collect, such as saliva, tears, urine, and sweat are considered as samples to investigate body components.

For example, your blood components keep changing according to the change in your diet, exercise, or the progress of disease. Consequently, changes appear in the components of saliva, tears, urine, and sweat.

However, some components are changeable while others are not, and there are also components that are not correlated with the blood. Therefore, detailed research is ongoing.

Among these components, I carry out research with a focus on technology that examines secreted components on the skin surface, that is, components of sweat. In fact, the components of sweat change according to the various conditions of the body. We are developing a wristwatch-type device for monitoring components in sweat to examine the changes.

Biological component measurement technology expected in various fields

This device for monitoring components in sweat is used exactly by placing it on the wrist like a wristwatch. It consists of a drug solution to collect sweat and extract its components, and a device that transmits the data. It can be used not only during daily life but also during exercise without interfering, allowing continuous measurement of changes in sweat composition.

Presently, we have completed a prototype, and further improvements are being made while collecting various data.

Collecting and analyzing information from many people (big data) about how components in sweat change over the course of a day will reveal what the data indicates. Thus, the change in the value will encourage individuals to be aware of their general health when they use this device.

Personally, I am very interested in lactic acid contained in sweat. Although lactic acid often appears to be produced by fatigue, more precisely, lactic acid itself is oxidized little by little as a source of energy and acts to reduce fatigue. In a situation where glucose is rapidly decomposed, or oxygen is insufficient in the activities of muscles and cells, lactic acid is produced and accumulated beyond its rate of consumption. Therefore, the level of lactic acid increases under intensive muscle training.

Researchers believe that while the lactic acid in sweat is not expected to reflect the lactic acid level in blood, it is produced by the action of cells when many of them produce sweat. However, if we can examine how the components of sweat change through long-term continuous measurements and find any relationship with the changes, new applications may become possible.

Students who play sport on a full scale are very interested in this study, and they are helping us accumulate data. In the future, we may be able to find data which is useful for training methods.

We also consider that the measurement of lactic acid may be useful not only in sports but also in medical care, and we are conducting joint research with St. Marianna University School of Medicine. For example, if sufficient oxygen is not delivered to the whole body owing to decreased lung function, hemorrhagic shock, or other cardiovascular problems, some parts of tissue become deficient in oxygen, resulting in an increase in blood lactate level. If it exceeds a certain level, it may be life-threatening.

For this reason, they want to measure the patient’s blood frequently, but there is a demand from clinical practice to avoid making holes in the skin and blood vessels as much as possible, considering the decline in the patient’s physical strength and immunity.

For example, the COVID-19, which is a big problem now, is known to cause pneumonia, which means a decline in lung function. Again, in this case, the body should become deficient in oxygen and the lactate level in the blood should increase. Although it may be difficult to determine the patient’s condition based solely on the lactic acid level of sweat, we expect that comprehensive investigation of the dynamics of various components will open new possibilities. Observational studies of lactic acid in sweat will acts as a foundation for such possibilities.

Our technology also allows us to access the skin as well as anywhere on the body surface, therefore, we can measure the components of saliva. By utilizing this feature, we are striving to apply this technology to the health of the mind as well as the body. For example, a protein called amylase in saliva is a well-known stress-induced substance.

In addition, some studies are investigating the relevance of a substance called oxytocin to the social relationships, attachment behavior, development, etc. of humans. It is considered that the oxytocin level increases when a mother’s breast milk is secreted or when a couple hold hands, etc. An association with autism spectrum disorder has also been pointed out.

We think that the activities of individuals will reveal activities of a cohort, or group, if we can measure how the secretion of these substances changes in daily life. For instance, if you think about a company structure, you may be able to quantitatively understand people’s relationships and the work environment of the company and department. This may be very useful information for the personnel division of a company and for job-hunting students. If we expand the scope of it a little more, we may see a picture of society as well. Wouldn’t it be interesting if you could visualize the information that substances in the body indicate, telling you that riding a train on a weekday morning is stressful, or more people feel happy in a certain place at night?

Recently, IoT (Internet of Things) technology has been widely used in our daily life in order to computerize our day-to-day life, increase convenience, and improve the quality of life by connecting various things to the Internet.

We want to develop a bio-sensing device that can measure body components easily, as a tool that enables us to handle information on our body and health, particularly information related to substances in our body, in such systems.

Concept of manufacturing that supports the latest system

It has been known for some time that sweat contains some blood components. However, measuring sweat actually requires a very difficult technique despite it seeming to be such an easy task.

For example, sweat is secreted from very small dermal tissue called sweat glands, and fluid evaporates from the moment it appears on the skin’s surface. This is the same as fine water droplets from a spray falling on a desk and evaporating immediately. Therefore, the sweat that appears on the skin must be collected immediately. This is because the concentration of sweat may change from that at the time of recreation even over a short time.

In addition, sweat does not uniformly secrete from the entire skin, and some of the components that are produced as part of sweat will remain on the skin even after fluid evaporates.

In other words, collecting sweat continuously and accurately to measure components of sweat was extremely difficult and not nearly as easy as it seems.

Accordingly, we have created a mechanism that constantly pumps harmless liquid called a carrier flow to the surface of the skin. Sweat dissolves into the carrier flow and is conveyed to the sensor, and constant flushing on the skin surface maintains its condition without leaving any part of the components on the skin.

Consequently, the change in the components of sweat during exercise, which was difficult to examine before, can be measured in real time.

In addition, in order to improve the accuracy of measurements, we fine-tuned the conditions, such as the selection of components of the reagent to be attached to the device and the temperature of the reagent.

In order for this data to be used in practice, it is important to establish a system with reproducibility and reliability and guarantee the rationality of the data.

Such ingenuities are derived by the accumulation of discoveries and inspiration that occur during a series of trial and error. Of course, there are many failures in the process, but it is important to thrive on such challenges. I think that is the basis of manufacturing.

In recent years, software development has become particularly popular in the field of information and AI that is attracting attention from students who aim to be engineers. However, no software can be of practical use without hardware.

In other words, hardware development is essential in the manufacturing of products that improve our quality of life. If you are interested in the structure and scheme of things on a daily basis, such interests can be utilized in various areas other than manufacturing.

We can think from the viewpoint of manufacturing in daily life and business, for example, when we look at new products or find handicrafts and buildings while travelling. This may trigger new discoveries or breakthroughs.

* The information contained herein is current as of March 2021.
* The contents of articles on Meiji.net are based on the personal ideas and opinions of the author and do not indicate the official opinion of Meiji University.
* I work to achieve SDGs related to the educational and research themes that I am currently engaged in.

Information noted in the articles and videos, such as positions and affiliations, are current at the time of production.