2003 by CRC Press LLC. Glucose is one of the most important carbohydrate nutrient sources and is fundamental to almost all biological processes. Quantification of glucose concentration is important in monitoring and analysis of agricultural products, control and regulation of cell culture, and diagnosis and control of human diseases including diabetes. A wide range of parameters, including glucose concentration range, volume of glucose solution available, and required accuracy, exist across these applications. For instance, the sugar concentration in many agricultural products (e.g., fruit juices) is hundreds of grams per liter while the glucose concentration for an on-line cell culture system may be in the milligrams per deciliter range. Additionally, the volume or, more importantly for optical approaches, the available optical path length for on-line process control and agricultural applications can be tens of centimeters while in vivo these are typically millimeters to centimeters. Consequently, the required glucose sensitivity in vivo needs to be orders of magnitude better than in the agricultural industry. Finally, the environmental challenges associated with in vivo monitoring make this problem more difficult than typical industrial applications because of a range of potential confounders that cannot be controlled. These include temperature and pH variations, confounding chemical species, pressure changes, and correlated physiological changes.
