Preliminary study of calibration-free continuous glucose monitoring with microdialysis technique

To develop an artificial pancreas, measurement of subcutaneous glucose concentration by using a microdialysis technique is required. However, long-term continuous measurement has not been achieved because the microdialysis probe recovery rate and the sensitivity of the glucose sensor decrease. To solve this problem, a new method for long-term continuous measurement of subcutaneous tissue glucose concentration using a microdialysis technique was developed. We assumed a model of standard glucose solutions of two different concentrations, which are perfused via a microdialysis probe inserted subcutaneously. The standard solutions are switched by changing the valve. One solution is higher in concentration than the tissue and the other is lower. By controlling the perfusion time ratio of the standard solutions, we will automatically be able to calculate the glucose concentration of the tissue from the ratio of perfusion time when the glucose sensor signal at the microdialysis probe outlet is steady. In our results, measurement error was less than 10% in the experiment using a larger-scaled hollow fiber instead of a microdialysis probe. This study suggests a method for continuous measuring of subcutaneous tissue glucose concentration without calibration.