Micrometer-scale light-addressable potentiometric sensor on an optical fiber for biological glucose determination

A novel light-addressable potentiometric sensor (LAPS), on the micrometer scale, is presented for rapid determination of blood and urine glucose. A LAPS chip with <150 μm working diameter is fabricated using standard semiconductor technique, and assembled onto an optical fiber of a laser module to form a micro-sized device. An active circuit design, containing on-board light driver and transimpedance amplifier, is introduced to simplify electronic connection and improve signal quality. Glucose-sensitive layer is obtained by drop-coating glucose oxidase onto the working surface of the LAPS. Under optimized optical and electrochemical conditions, the proposed sensor is used to detect glucose in laboratorial and real samples. In a wide range as 0.01-100 mM, a log-linear relationship is well established, and the response time is less than 10 s. Limit of detection and limit of quantitation of this method are found to be 0.003 and 0.01 mM, respectively. Data from the proposed method are validated with those from a certified clinical analyzer, and no statistic difference is found.