Abstract

The Next Generation Self Monitoring of Blood Glucose (SMBG) and Continuous Glucose Monitoring (CGM)

Koji Sode, Chair, Tokyo University of Agriculture and Technology

The 1st generation blood glucose monitoring systems employed oxygen as the electron acceptor and measuring either the consumption of oxygen or the liberation of hydrogen peroxide. The 2nd generation sensors, artificial electron acceptors (electron mediators) were employed. Current glucose sensing systems, utilized in the Self Monitoring of Blood Glucose (SMBG) dedicating for glycemic control of diabetic patients, are based on the 2nd generation principle. The recent most remarkable progress is the use of fungi derived FAD dependent glucose dehydrogenases or often referred as GDH-FAD, focusing their narrow substrate specificity, especially their lack of activity toward maltose. The 3rd generation sensors, although commercial product has not yet been reported, are direct electron transfer principle. This principle employs the enzymes capable of the direct electron transfer to the electrode, thus eliminating the use of artificial electron mediators and avoiding errors due to variations in the concentration of oxygen in blood samples. Besides, continuous glucose monitoring (CGM) is expected to become an ideal way to monitor glycemic levels in diabetic patients, as well as a useful tool to control the blood glucose level in combination with an insulin pump, thus realizing the concept of an artificial pancreas. Current CGM systems employ either the 1st or 2nd generation of enzyme glucose sensors, using GOx as the enzyme. In this paper, I introduce the challenge in the development of the 3rd generation of SMBG and CGM sensor, based on the Direct Electron Transfer (DiET) technology. The sensor employs a unique bacterial glucose dehydrogenase enzyme (FAD-GDH) harboring flavin adenine dinucleotide (FAD) as the catalytic cofactor in its catalytic subunit and also cytochrome c as the electron transfer subunit. The sensor does not require any artificial electron acceptors to show sensor response to glucose in the sample. The in vitro and in vivo performances of DiET tech