Noninvasive glucose sensing utilizing a digital closed-loop polarimetric approach.

A polarimetric glucose sensor utilizing a digital closed-loop controller was designed and implemented during this study. Its potential as a noninvasive glucose sensor was evaluated in vitro for both glucose-doped water and bovine aqueous humor mediums. A physiological hyperglycemic concentration range was used in both calibration and validation of each set of experiments. Ideally, the end application of this system could estimate blood glucose concentrations indirectly by measuring the amount of rotation of a light beam's polarization state after it propagates through the aqueous humor contained within the anterior chamber of the eye. The polarimeter designed in this study differs from similar investigated systems in that it utilizes a digital closed-loop control system. This type of controller was implemented in order to further improve system repeatability and stability without sacrificing accuracy. Unique to this investigation, independent validation sets other than those used to create each respective calibration model were obtained. The results of the glucose-doped water experiments yielded mean standard errors of prediction for calibration and validation of 6.91 and 8.84 mg/dl, respectively. The mean standard errors of prediction during calibration and validation of the glucose-doped aqueous humor experiments were higher at 27.20 and 27.47 mg/dl, respectively, due to medium degradation over time while exposed to air.