Continuous glucose monitoring by means of mid-infrared transmission laser spectroscopy in vitro

摘要

The continuous surveillance of glucose concentration reduces short-term risks and long-termncomplications for people with diabetes mellitus, a disorder of glucose metabolism. As a first stepntowards the continuous monitoring of glucose, reagent-free transmission spectroscopy in the midinfrarednregion has been carried out in vitro using a quantum cascade laser and an optical silver halidenfiber. A 30 mm gap in the fiber allowed for transmission spectroscopy of aqueous glucose solutions atna wavelength of 9.69 mm, which is specific to a molecular vibration of glucose. A noise-equivalentnconcentration as low as 4 mg/dL was achieved at an average power of 1.8 mW and an integration timenof 50 s. This is among the most precise of glucose measurements using mid-infrared spectroscopy. Evennwith the very low average laser power of 0.07mWthe sensitivity of previous results (using a fiber opticalnevanescent field analysis) has been improved upon by almost one order of magnitude. Finally, thenimpact of potentially interfering substances such as other carbohydrates was analyzed.