Two-Dimensional Array ATP/ADP Sensitive Image Sensor with a Uniform Distribution of Chemically Immobilized Apyrase

ATP and ADP are the major energy source in metabolism of cells, and furthermore ATP works as an important extracellular signaling material. ATP bioimaging is required to understand their metabolism. In this paper, a label-free ATP/ADP image sensor was fabricated using a 128 x 128 (16 k) pixel array semiconductor CCD-type pH image sensor and Apyrase. The principle is based on measuring protons produced by the enzyme reaction between Apyrase and ATP or ADP. In order to put a uniform potential response of the sensor into practice, two different methods, (3-APTES and CEST), which chemically fixed N-terminal of Apyrase with the sensor were examined. The sensor modified by the CEST method had a quite clean surface microscopically and demonstrated a fine real-time image monitoring the ATP concentration. The potential response of the image sensor was characterized; effect of buffer solution, calibration curves of ATP and ADP, durability, the limit of detection (LOD) for ATP, and the response of time. The potential distribution for effective pixels to ATP concentration was narrow, single and symmetrical. Due to 16K sensing pixels finely responding to ATP concentration uniformly, the LOD of ATP concentration (10 mu M) was exactly determined with a statistical treatment.