Blood sugar measured by laser may do away with pin pricks

Date: Aug-22-2014 Researchers are working on a way to use laser technology to measure blood

glucose non-invasively. While there is still a way to go before they have a laser device that is

portable and suitable for home use, they believe one day it will replace the need for diabetics

to draw blood to test their glucose levels.

In the journal Biomedical Optics Express, the team of electrical engineers, from

Princeton University, NJ, describes how they used their prototype device to measure blood sugar

by directing the laser at a person's palm.

Senior author Claire Gmachl, the Eugene Higgins Professor of Electrical Engineering at

Princeton, says:

"With this work we hope to improve the lives of many diabetes sufferers who depend on frequent

blood glucose monitoring."

Laser beam penetrates skin and is absorbed by glucose

The device works by sending a laser beam through skin cells - without causing damage - to be

absorbed by sugar molecules. The target is not blood sugar as such, but the sugar content of

dermal interstitial fluid, which has a strong correlation with blood sugar.

The new monitor uses a laser, instead of blood sample, to read blood sugar levels. The laser is directed at the person's palm, passes through skin cells and is partially absorbed by sugar molecules, allowing researchers to calculate blood sugar levels.
Image credit: Princeton

The amount of absorption of the laser beam is thus an indicator of the amount of glucose in

the blood.

The team was surprised at how accurate the readings turned out to be. Current glucose

monitors that patients use at home are required to show readings within 20% of the patient's

actual blood level.

Lead author Sabbir Liakat, a graduate student in electrical engineering, says even their early

version of the laser system met this requirement, and the latest version is 84% accurate.

The challenge now is to improve the technology - and not least to bring down the scale.

When they started working on the idea, the device covered an average lab bench and needed an

elaborate system to keep it cool.

Prof. Gmachl says they have solved the cooling problem - the system now works at room

temperature - but they still have to work out how to make the technology smaller.

They aim to develop a mobile device they can take to clinics and put through more tests and

collect a larger set of data to work with.

The device uses a 'quantum cascade laser' to produce mid-infrared light

The system uses infrared laser light, which is just beyond the spectrum light visible to the

human eye. Medical devices currently use near-infrared, a band that has slightly longer

wavelengths than the red that the human eye can see. Near-infrared is not blocked by water and

can thus be used in the body.

The quantum cascade laser allows the team to select the frequency they need in the mid-infrared region, and also because of recent improvements in the technology, it provides the increased power and stability needed to penetrate the skin.
Image credit: Princeton

But near infrared does not interact with chemicals in the skin - for that you have to move to

slightly longer wavelengths in the mid-infrared region. At this wavelength, the laser light is

absorbed by blood sugar and is not much affected by other chemicals in the skin.

However, mid-infrared laser light is more difficult to harness with standard lasers, and it

also requires higher power and stability in order for the beam to penetrate the skin and scatter

off bodily fluid.

But as sometimes happens in projects where people work tirelessly to achieve their goals -

there was a breakthrough. This came when they tried a new type of device called a 'quantum

cascade laser.'

The quantum cascade laser allows the team to select the frequency they need in the mid-infrared region, and also because of recent improvements in the technology, it provides the

increased power and stability needed to penetrate the skin.

Small study shows average readings meet required clinical accuracy

In their study paper they describe how they measured the blood sugar of three healthy

volunteers before and after they each ate 20 jellybeans. The researchers also measured the

resulting rise in blood sugar with the conventional finger-prick test.

The team repeated the experiment and took measurements several times over several weeks. The

results showed that while the laser device's average readings had errors larger than standard

blood sugar monitors, they were within the range required for clinical accuracy.

The team is excited by the potential their discovery offers because, as Prof. Gmachl explains,

"the quantum cascade laser can be designed to emit light across a very wide wavelength range, its

usability is not just for glucose detection, but could conceivably be used for other medical

sensing and monitoring applications."

The National Science Foundation, the Wendy and Eric Schmidt Foundation, Daylight Solutions

Inc., and Opto-Knowledge Systems helped to fund the study.

Recently, Medical News Today also learned how the discovery of a glucose sensor in the brain may

lead to new diabetes treatments.

Written by Catharine Paddock PhD

View all articles written by Catharine, or follow her on:

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.