Development of a Highly-Miniaturized Continuous Biosensor for Lactate and Glucose

There is a need to develop minimally-invasive devices that will allow continuous and simultaneous measurement of more than one metabolic analyte. Two such analytes are glucose and lactate. The benefits of continuously measuring these analytes in subcutaneous interstitial fluid include early detection of physical exhaustion, for example in firefighters or warfighters, and critical care monitoring of patients with heart failure, respiratory failure or shock. To minimize pain during subcutaneous insertion, the device must be small in diameter. We propose to create a minimally-invasive fine-wire based biosensor whose diameter is no more than 0.35 mm that can be inserted through a 21-23 gauge trocar. The sensor will have two wire electrodes devoted to measurement of lactate and glucose and one electrode that will serve as the common reference. The major challenge will be to enhance the sensitivity of the device to lactate and glucose despite its small electrode area. Techniques that will be utilized to accomplish this goal will include development of sensitive assays for glucose oxidase and lactate oxidase to optimize enzyme loading, optimization of glutaraldehyde crosslinking, optimization of membrane thickness, and etching of the platinum electrode surface in order to enhance amperometric detection and membrane adherence.