Needle-free diabetes testing

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  • Published: Sep 1, 2010
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Needle-free diabetes testing

A new device based on Raman spectroscopy has been developed by scientists at MIT to help patients with diabetes monitor their blood glucose levels without needing to prick their fingers to take a blood sample.

People with Type 1 diabetes must ensure that they monitor their blood glucose levels in order to avoid the potentially lethal complications of the disease, such as organ damage caused by too much glucose in the blood and hypoglycaemia, in which organs including the brain are deprived of fuel. Most patients are forced to prick their fingers several times a day to draw blood for testing.

Researchers at Massachusetts Institute of Technology's Spectroscopy Laboratory hope to remedy that situation for diabetes sufferers and are working on a non-invasive way to measure blood glucose levels using light.

The concept of a light-based blood-glucose monitor was first postulated fifteen years ago by MIT physicist the late Michael Feld who was head of the Spectroscopy Laboratory. He reasoned that Raman spectroscopy would be the most appropriate tool to develop for such a test. A Raman device could obtain a measure of blood glucose concentration simply by scanning a patient's skin on their arm or finger with near-infrared light.

Now, two graduate students in the laboratory, Ishan Barman and Chae-Ryon Kong, have developed a small Raman spectrometer, not much bigger than a standard notebook computer that could be used by physicians and patients alike. The device would be a boon to the lives of millions of Type 1 diabetes patients the world over.

The MIT team was faced with a major obstacle in that to be effective they must circumvent the problem of near-infrared light penetrating the skin by only about half a millimetre. The technique would thus be determining not blood glucose but the fluid that bathes skin cells, the interstitial fluid. The key was to devise an algorithm that relates the two concentrations, using interstitial fluid concentration as an accurate proxy of blood glucose levels.

So far, so simple.

However, the correlation between these two measurements is affected by whether or not someone has ingested something sweet. Blood glucose rises rapidly immediately after eating or drinking something containing sugar whereas the interstitial concentration lags behind, taking some five to ten minutes to rise to its peak level. In other words, interstitial fluid measurements do not give an accurate picture of what is happening in the bloodstream and so a patient could administer insulin inappropriately.

The team, which also includes Ramachandra Rao Dasari, associate director of the Spectroscopy Lab, and former postdoctoral researcher Gajendra Pratap Singh, has now addressed this time lag using a new calibration method they call Dynamic Concentration Correction (DCC). This new algorithm incorporates the rate at which glucose diffuses from the blood into the interstitial fluid.

Writing in the journal Analytical Chemistry, the team describes how the study tested the new system on ten healthy -volunteers. The researchers used DCC-calibrated Raman spectroscopy to significantly boost the accuracy of blood glucose measurements. They saw an average improvement of about 15 percent in some volunteers and up to 30 percent in others.

The success of the system will hinge on a full clinical trial in healthy volunteers, which Barman and Kong plan to launch in Autumn 2010 with funding from the National Institutes of Health and National Center for Research Resources.

Chemist Michael Morris, of the University of Michigan, is enthusiastic about the work. "Getting optical glucose measurements of any sort is something people have been trying to do since the 1980s," he explains. Researchers usually report that they can get good measurements one day, but not the next, or that it only works for a few people, a universal calibration system has, until now, remained elusive. Morris adds that the non-invasive nature of Raman spectroscopy could help boost quality of life for diabetes patients, but that to be practical, any device would need to become more affordable and very simple to use. The Spectroscopy Lab researchers believe that the smaller machine they are now developing should substantially drive down costs by miniaturizing and reducing the complexity of the instrument.

"The new device based on Raman spectroscopy is currently under development and we hope to have a functional prototype in the next two years," Barman told SpectroscopyNOW. "However, at this time, we have a portable instrument, which is relatively large, the size of a shopping cart, and can only be used for clinical studies. In fact, our feasibility studies which will start this Fall will be making use of this portable instrument that can be wheeled into a clinic but cannot be used for personal use."

"We will be starting [clinical] studies in September 2010," Barman told us. "We expect the initial series of studies to complete by the middle of next year. In the first trials, we will be testing our instrumentation and methodologies on healthy human volunteers. In the next set of investigations, we will be incorporating our primary target population of Type I and II diabetics. For our purposes, there is no difference between any diabetic patient (Type I, II or gestational) - however, if successfully implemented our technology would be most beneficial to Type I patients who need to perform 6-12 measurements per day."





Photo: Patrick Gillooly
Needle-free glucose monitoring
(Credit: Patrick Gillooly, MIT)

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