Researchers from the Indian Institute of Science have developed two new methods to detect glucose levels in the blood. Both the method use state of the art technology, and can potentially help in early detection of diabetes.
One of the methods is developed using the 'field effect transistor', a device without which our technology dominated world wouldn't have existed. The other method uses what is called a 'Bragg grating', a device that is used in applications ranging from measuring pulse in humans to aircraft health monitoring. However, both the methods are radically different from the method presently used in diagnostic laboratories.
“To detect glucose, hospitals use chemical based methods that are complicated and time consuming. Our first technology is based on electrical signals and the second uses the principles of optics”, says Prof Ajay Sood, Professor of Physics, Indian Institute of Science, and a Fellow of the Royal Society, London. Prof Sood and Prof Asokan along with Prof Sampath led the development of the novel technologies. Prof Sood and Prof Asokan are not new to developing this kind of technologies: using Fibre Bragg grating, they have developed other medical diagnostic platforms in the past.
Interestingly, both the methods use functionalized graphene, a material with excellent properties. Graphene is simply a single layer of carbon atoms held together by chemical bonds. However, it's mechanical, optical, and electrical properties defy its structural simplicity. It also has a larger surface area . Graphene oxide is both hydrophobic as well as hydrophilic in nature , which makes it possible to attach it to glass fibre.
For their initial experiments (published in Sensors and Actuators : B , August 2015), Professor Sood’s team made a FET of graphene functionalized with APBA molecules which have specificity to attach to the glucose molecules. These sensors could sense a glucose at a concentration of 2 nanomolars, a remarkable sensitivity. To get a feel for that, imagine searching for four people from a population that is ten times that of India, and catching them!
After successfully demonstrating a glucose detector based on the field effect transistor, Prof Sood and Prof Asokan teamed up to develop a detector based on 'Fibre Bragg grating'( published in Journal of Biophotonics , August 2015). A Bragg grating is an interesting device. It reflects one wavelength, like a mirror, and allows other wavelengths to pass through, like a piece of transparent glass. The reflected wavelength depends on an optical property called the refractive index of the shell material .The researchers removed the clad material of the optical fibre and coated the grating part of the fibre with graphene functionalized with APBA molecules. When exposed to blood, the glucose molecules that are attached to haemoglobin, bind to APBA molecules which changes the wavelength reflected by the grating. By calibrating the change in reflected wavelength, the researchers could accurately measure the concentration of glucose in the blood. The device is sensitive enough to detect glucose in an ocean of healthy blood, and can detect glycolated haemoglobin too.
Though both the technologies look promising, Prof Sood feels that it's too early to compare and contrast them. With the ever increasing demand for cheaper, quicker, and more accurate medical diagnostic devices, these technologies may well develop into usable products one day.
About the authors
All the authors are at the Indian Institute of Science, Bangalore. S. Sridevi ( a graduate student)and Professor S. Asokan are from the Department of Instrumentation and Applied Physics. K. S. Vasu ( graduate student )and Professor A. K. Sood are from the Department of Physics. Prof .S. Sampath is from the Department of Inorganic and Physical Chemistry. Prof S. Asokan is also at the Robert Bosch Centre for Cyber Physical Systems, Indian Institute of Science, Bangalore.
Contact: Prof Ajay Sood at 080-2293 2964.