Blood testing is the standard option for checking glucose levels, but a new technology described in the journal Advanced Materials could allow noninvasive testing via a contact lens that samples glucose levels in tears.
“There’s no noninvasive method to do this,” said Wei-Chuan Shih, a researcher with the University of Houston (UH) who worked with colleagues at UH and the Korea Advanced Institute of Science and Technology to develop the project. “It always requires a blood draw. This is unfortunately the state of the art.”
But glucose is a good target for optical sensing, and especially for what is known as surface-enhanced Raman scattering spectroscopy, said Shih.
The paper describes the development of a tiny device, built from multiple layers of gold nanowires stacked on top of a gold film and produced using solvent-assisted nanotransfer printing, which optimized the use of surface-enhanced Raman scattering to take advantage of the technique’s ability to detect small molecular samples.
Surface-enhanced Raman scattering-named for Indian physicist C.V. Raman, who discovered the effect in 1928-uses information about how light interacts with a material to determine properties of the molecules that make up the material.
The device enhances the sensing properties of the technique by creating “hot spots,” or narrow gaps within the nanostructure which intensified the Raman signal, the researchers said.
“It should be noted that glucose is present not only in the blood but also in tears, and thus accurate monitoring of the glucose level in human tears by employing a contact-lens-type sensor can be an alternative approach for noninvasive glucose monitoring,” the researchers wrote.
Scientists know that glucose is present in tears, but Shih said how tear glucose levels correlate with blood glucose levels hasn’t been established. The more important finding, he said, is that the structure is an effective mechanism for using surface-enhanced Raman scattering spectroscopy.
Although traditional nanofabrication techniques rely on a hard substrate-usually glass or a silicon wafer-Shih said researchers wanted a flexible nanostructure, which would be more suited to wearable electronics. The layered nanoarray was produced on a hard substrate but lifted off and printed onto a soft contact, he said.
This article was adapted from information provided by University of Houston.