Gingival Crevicular Fluid Collecting Device for Noninvasive Blood Glucose Monitoring

Objective: We have been focusing on the development of noninvasive methods of measuring the blood glucose level by analyzing painlessly collected gingival crevicular fluid (GCF). Its flow rate is only 2 to 3 mL per hour per tooth. We fabricated a GCF-collecting device used for collecting and determination of the GCF, which was designed to be disposable. A clinical evaluation of the time-course changes in measurement accuracy using this GCF-collecting device was performed. Methods: Enclosed within a GCF-collecting device is an enzyme testing tape used for the determination of the GCF glucose level. It has a capillary drain and capillary action is used to pump GCF automatically. Three sheets of film are laminated in order to make the capillary drain. The middle film has a drain and the plain films on each side are used as a cover. The drain draws samples to a built-in testing tape between these films. Glucose tolerance test was performed on four normal subjects (two male, two female, aged 22±1 years, BMI of 19.8±1.0 kg/m², mean±S.D.) as an in vivo evaluation. Next, time-course changes of the correlation coefficient of blood and GCF glucose levels were measured in the subjects one or two times per day for two weeks. Results: The correlation coefficient was initially 0.92±0.10 but lowered to 0.75±0.20 over the two weeks. It can be speculated that a major factor that, may reduce the correlation between the two glucose levels, could be contamination by saliva of the GCF because the accumulated correlation coefficient was lowered down continuously at every step. Conclusion: The present study demonstrated that if contamination by saliva can be reduced, this procedure may be used to estimate blood glucose level noninvasively.