doi:10.1038/nindia.2014.140 Published online 27 October 2014
Researchers have fabricated a sensitive, enzyme-free sensor that can rapidly measure low concentrations of glucose1. They made the sensor using surfactant-containing magnetic nanoemulsions. It is potentially useful for measuring glucose levels in diabetic patients, foods and biochemical samples.
Existing glucose sensors employ enzymes such as glucose oxidase. These sensors take considerable time to detect glucose, making them unsuitable for many applications. To devise an effective and fast glucose sensor, the researchers encapsulated ferrimagnetic iron oxide nanoparticles with an oil-in-water emulsion. They then stabilized this nanoemulsion by adding the surfactant sodium dodecyl sulphate. Sophisticated imaging revealed that the magnetic nanoemulsions consist of nanoscale droplets.
The researchers evaluated the glucose-sensing efficacy of the magnetic nanoemulsions by exposing them to different concentrations of glucose in the presence of a constant external magnetic field and ambient light. They discovered that the magnetic field caused the droplets in nanoemulsions form one-dimensional chain-like structures.
The nanoscale droplets are separated by tiny distances, which vary depending on the glucose concentration. These changes in the average interdroplet distance caused the magnetic nanoemulsions to reflect light of different colours. For example, the magnetic nanoemulsions reflected green light at normal glucose levels, whereas they reflected orange light at diabetic glucose levels.
The researchers say that this method enables glucose detection by visual observation without the need to use electronic devices. “This enzyme-free method can detect glucose in milliseconds, making it suitable for developing the next generation of smart glucometers”, says John Philip, a senior author of the study.