Japanese Researchers Used Fluorescence to Accurately Measure Blood Glucose Levels in Mice

In Japan, researchers are developing a new in vivo diagnostic test technology that can monitor blood glucose in real time. Pathologists and clinical laboratory managers will quickly grasp the implications of these implantable, fluorescable microbeads that can be used to accurately and continuously measure blood sugar levels.

The Japanese researchers created tiny microbeads that glow when in contact with glucose. The beads are small enough to be injected directly into the blood stream and respond rapidly when glucose levels change. According the Shoji Takeuchi, lead researcher at the University of Tokyo’s Life Bio Electromechanical Autonomous Nano Systems Center, the microbeads are uniquely qualified to monitor diabetics’ blood sugar levels.

This image shows a mouse possessing implanted glucose-responsive fluorescent hydrogel microbeads (GF-beads) in its ear. GF-beads can be clearly detected through the skin layers. It is evident that GF-beads have a feasibility to apply for in vivo transdermal glucose monitoring. (Sourced from the PNAS report’s support materials.)

Potential Major Breakthrough in Blood-glucose Monitoring

“We found that our fluorescent beads provide sufficient intensity to transdermally monitor glucose concentrations in vivo,” wrote the researchers in “Injectable Hydrogel Microbeads For Fluorescence-based in Vivo Continuous Glucose Monitoring,” published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS). “The fluorescence intensity successfully traced the blood glucose concentration fluctuation, indicating our method has potential uses in highly-sensitive and minimally invasive continuous blood glucose monitoring.”

Could Clinical Laboratory Tests Use These Fluorescent Microbeads?

These tiny round microparticles emit colors of varying intensity when exposed to ultra-violet (UV) light. Thus, they become visible and the intensity of their color can be measured against background materials providing contrast. Their round shape also makes them highly useful in lab simulations.

“Because the fluorescent microbeads do not require external links or power sources to provide a read out,” wrote the scientists in the article’s abstract, “they could be used to fabricate minimally invasive glucose sensors for people who need to continuously monitor their blood glucose levels.”

The researchers implanted the microbeads in the ears of mice, then bombarded them with UV light and measured the intensity of the beads glow against the amount of glucose already existing in the mice.

“We synthesized a fluorescent monomer composed of glucose-recognition sites, a fluorogenic site, spacers, and polymerization sites,” wrote the scientists. “The spacers are designed to be long and hydrophilic for increasing opportunities to bind glucose molecules; consequently, the fluorescent monomers enable high-intensive responsiveness to glucose.

“We then fabricated injectable-sized fluorescent polyacrylamide hydrogel beads with high uniformity and high throughput,” they continued. ‘We found that our fluorescent beads provide sufficient intensity to transdermally monitor glucose concentrations in vivo. The fluorescence intensity successfully traced the blood glucose concentration fluctuation, indicating our method has potential uses in highly-sensitive and minimally invasive continuous blood glucose monitoring.”

There is always plenty of speculation about when and how the integration of in vivo diagnostics and in vitro diagnostics will occur. Now, pathologists and clinical laboratory managers have an intriguing example of how microbead technology could enable an in vivo test for the continuous and accurate monitoring of blood glucose levels in diabetics.

This research project demonstrates how new medical laboratory technology has the potential to not only shift medical laboratory testing away from today’s high-volume centralized clinical laboratories, but also to even supplement or replace near-patient and point-of-care (POC) testing—even as patients benefit from a more convenient and precise diagnostic test.

–Michael McBride

Related Information:

Injectable Hydrogel Microbeads For Fluorescence-based in Vivo Continuous Glucose Monitoring Abstract

MPEG Movie Showing Glowing Microbeads in Ear of a Lab Mouse

Research Paper Supporting Information

Fluorescent Microspheres—Properties and Applications