Research on correlation of glucose level in saliva and blood based on fluorometric sensing method

Abstract

In modern society, diabetes mellitus has become a global issue because the number of diabetic patients is rapidly increasing worldwide. The patients with diabetes require continuous monitoring of their blood glucose level every day. However, they have still trouble with measuring blood glucose level. Most of the current blood glucose meters are invasive-type so patients suffer with pain and are prone to infection at the subcutaneous injection. In decade, many types of non-invasive glucose meter have been researched to solve these problems and researchers are trying to measure the blood glucose level indirectly by using a body fluid instead of blood. There are several kinds of body fluid: sweat, urine, tear and saliva. Among them, saliva is easy to collect and it is already known that the biological properties of saliva are closely related to blood so it is suitable for non-invasive type of glucose level measuring. Since it is not well-known whether saliva glucose level can reflect blood glucose level, however, elucidation of the correlation of glucose level in saliva and blood is the most important part. Moreover saliva has an extremely low glucose concentration compared to blood so it requires a precise sensing method for measurement. Meanwhile, the biological and chemical sensing by optical technologies has been great interest and rapidly growing because of their high sensitivity and accuracy. Especially, a fluorometric sensing method is not only simple, but also highly sensitive, so it is used for measuring the glucose level in this thesis. The fluorometric method uses material which has fluorescence property after chemical reaction. The Amplex Ultra Red (AUR) is used as a fluorometric material because of stability over a wide pH range, rapid reaction rate and sensitivity. In AUR fluorometric method, following 3 chemicals are used

Horseradish peroxidase (HRP), glucose oxidase (GOD) and AUR. The ratio of these compounds is the most important to property of AUR assay. Generally, the saliva has 0 to 2 mg/dL glucose level range and results of ratio changing experiments have clearly shown that AUR: HRP: GOD: Glucose =2:2:1:3 is an optimal ratio in this range of glucose concentration. The saliva glucose concentration is measured by above AUR assay condition. However, there is only a weak correlation of glucose level in saliva and blood in raw data because there are several factors that can influence to the correlation. These factors are different from individual person, measurement time and time interval between generation and secretion of saliva. So the correlation is recalculated with several factors which can influence to salivary glucose. After calibration, the correlation of glucose level becomes high enough to measure the blood glucose level.